Add constrained_t to fold

Co-authored-by: Radosław Rowicki <35342116+radrow@users.noreply.github.com>

.circleci/config.yml

@@ -3,7 +3,7 @@ version: 2.1
 executors:
   aebuilder:
     docker:
-      - image: aeternity/builder:bionic-otp24
+      - image: aeternity/builder:xenial-otp21
         user: builder
     working_directory: ~/aesophia
 

.github/workflows/docs-develop.yml

@@ -13,6 +13,10 @@ jobs:
       - uses: actions/setup-python@v2
         with:
           python-version: 3.8
+      - uses: actions/cache@v2
+        with:
+          path: ~/.cache/pip3
+          key: ${{ runner.os }}-pip-${{ hashFiles('.github/workflows/requirements.txt') }}
       - run: pip3 install -r .github/workflows/requirements.txt -U
       - run: git config --global user.email "github-action@users.noreply.github.com"
       - run: git config --global user.name "GitHub Action"

.github/workflows/docs-release.yml

@@ -13,6 +13,10 @@ jobs:
       - uses: actions/setup-python@v2
         with:
           python-version: 3.8
+      - uses: actions/cache@v2
+        with:
+          path: ~/.cache/pip3
+          key: ${{ runner.os }}-pip-${{ hashFiles('.github/workflows/requirements.txt') }}
       - run: pip3 install -r .github/workflows/requirements.txt -U
       - run: git config --global user.email "github-action@users.noreply.github.com"
       - run: git config --global user.name "GitHub Action"

.github/workflows/requirements.txt

@@ -1,5 +1,5 @@
 mkdocs==1.2.4
-mkdocs-simple-hooks==0.1.5
-mkdocs-material==7.3.6
-mike==1.1.2
-pygments==2.12.0
+mkdocs-simple-hooks==0.1.3
+mkdocs-material==7.1.9
+mike==1.0.1
+pygments==2.11.2

CHANGELOG.md

@@ -6,13 +6,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ### Added
-### Changed
-### Removed
-
-## [7.0.0]
-### Added
-- Added support for `EXIT` opcode via `exit : (string) => 'a` function (behaves same as `ABORT`, but consumes all gas).
-- Compiler warnings for the following: shadowing, negative spends, division by zero, unused functions, unused includes, unused stateful annotations, unused variables, unused parameters, unused user-defined type, dead return value.
+- Compiler warnings for the follwing: shadowing, negative spends, division by zero, unused functions, unused includes, unused stateful annotations, unused variables, unused parameters, unused user-defined type, dead return value.
 - The pipe operator |>
   ```
   [1, 2, 3] |> List.first |> Option.is_some  // Option.is_some(List.first([1, 2, 3]))
@@ -22,7 +16,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   function sum(l : list(int)) : int = foldl((+), 0, l)
   function logical_and(x, y) = (&&)(x, y)
   ```
-- Contract interfaces polymorphism
+- Add comparable typevar constraints (`ord` and `eq`)
+  ```
+  lt : 'a is ord ; ('a, 'a) => bool
+  lt(x, y) = x < y
+
+  is_eq : 'a is eq ; ('a, 'a) => bool
+  is_eq(x, y) = x == y
+  ```
 ### Changed
 - Error messages have been restructured (less newlines) to provide more unified errors. Also `pp_oneline/1` has been added.
 - Ban empty record definitions (e.g. `record r = {}` would give an error).
@@ -352,8 +353,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Simplify calldata creation - instead of passing a compiled contract, simply
   pass a (stubbed) contract string.
 
-[Unreleased]: https://github.com/aeternity/aesophia/compare/v7.0.0...HEAD
-[7.0.0]: https://github.com/aeternity/aesophia/compare/v6.1.0...v7.0.0
+[Unreleased]: https://github.com/aeternity/aesophia/compare/v6.1.0...HEAD
 [6.1.0]: https://github.com/aeternity/aesophia/compare/v6.0.2...v6.1.0
 [6.0.2]: https://github.com/aeternity/aesophia/compare/v6.0.1...v6.0.2
 [6.0.1]: https://github.com/aeternity/aesophia/compare/v6.0.0...v6.0.1

docs/sophia_features.md

@@ -134,155 +134,6 @@ main contract IntHolderFactory =
 In case of a presence of child contracts (`IntHolder` in this case), the main
 contract must be pointed out with the `main` keyword as shown in the example.
 
-### Contract interfaces and polymorphism
-
-Contracts can implement one or multiple interfaces, the contract has to define
-every entrypoint from the implemented interface and the entrypoints in both
-the contract and implemented interface should have compatible types.
-
-```
-contract interface Animal =
-  entrypoint sound : () => string
-
- contract Cat : Animal =
-  entrypoint sound() = "Cat sound"
-```
-
-Contract interfaces can extend other interfaces. An extended interface has to
-declare all entrypoints from every parent interface. All the declarations in the extended
-interface must have types compatible with the declarations from the parent
-interface.
-
-```
-contract interface II =
-  entrypoint f : () => unit
-
-contract interface I : II =
-  entrypoint f : () => unit
-  entrypoint g : () => unit
-
-contract C : I =
-  entrypoint f() = ()
-  entrypoint g() = ()
-```
-
-It is only possible to implement (or extend) an interface that has been already
-defined earlier in the file (or in an included file). Therefore recursive
-interface implementation is not allowed in Sophia.
-
-```
-// The following code would show an error
-
-contract interface X : Z =
-     entrypoint x : () => int
-
- contract interface Y : X =
-     entrypoint x : () => int
-     entrypoint y : () => int
-
- contract interface Z : Y =
-     entrypoint x : () => int
-     entrypoint y : () => int
-     entrypoint z : () => int
-
- contract C : Z =
-     entrypoint x() = 1
-     entrypoint y() = 1
-     entrypoint z() = 1
-```
-
-#### Subtyping and variance
-
-Subtyping in Sophia follows common rules that take type variance into account. As described by [Wikipedia](https://en.wikipedia.org/wiki/Covariance_and_contravariance_(computer_science)), 
-
->Variance refers to how subtyping between more complex types relates to subtyping between their components.
-
-This concept plays an important role in complex types such as tuples, `datatype`s and functions. Depending on the context, it can apply to positions in the structure of a type, or type parameters of generic types. There are four kinds of variances:
-
-- covariant
-- contravariant
-- invariant
-- bivariant
-
-A type is said to be on a "covariant" position when it describes output or a result of some computation. Analogously, position is "contravariant" when it is an input, or a parameter. Intuitively, when a part of the type is produced by values of it, it is covariant. When it is consumed, it is contravariant. When a type appears to be simultaneously input and output, it is described as invariant. If a type is neither of those (that is, it's unused) it's bivariant. Furthermore, whenever a complex type appears on a contravariant position, all its covariant components become contravariant and vice versa.
-
-Variance influences how subtyping is applied. Types on covariant positions are subtyped normally, while contravariant the opposite way. Invariant types have to be exactly the same in order for subtyping to work. Bivariant types are always compatible.
-
-A good example of where it matters can be pictured by subtyping of function types. Let us assume there is a contract interface `Animal` and two contracts that implement it: `Dog` and `Cat`.
-
-```sophia
-contract interface Animal =
-  entrypoint age : () => int
-  
-contract Dog : Animal =
-  entrypoint age() = // ...
-  entrypoint woof() = "woof"
-  
-contract Cat : Animal =
-  entrypoint age() = // ...
-  entrypoint meow() = "meow"
-```
-
-The assumption of this exercise is that cats do not bark (because `Cat` does not define the `woof` entrypoint). If subtyping rules were applied naively, that is if we let `Dog => Dog` be a subtype of `Animal => Animal`, the following code would break:
-
-```sophia
-let f : (Dog) => string  = d => d.woof()
-let g : (Animal) => string  = f
-let c : Cat = Chain.create()
-g(c)  // Cat barking!
-```
-
-That is because arguments of functions are contravariant, as opposed to return the type which is covariant. Because of that, the assignment of `f` to `g` is invalid - while `Dog` is a subtype of `Animal`, `Dog => string` is **not** a subtype of `Animal => string`. However, `Animal => string` **is** a subtype of `Dog => string`. More than that, `(Dog => Animal) => Dog` is a subtype of `(Animal => Dog) => Animal`.
-
-This has consequences on how user-defined generic types work. A type variable gains its variance from its role in the type definition as shown in the example:
-
-```sophia
-datatype co('a) = Co('a) // co is covariant on 'a
-datatype ct('a) = Ct('a => unit) // ct is contravariant on 'a
-datatype in('a) = In('a => 'a) // in is invariant on 'a
-datatype bi('a) = Bi // bi is bivariant on 'a
-```
-
-The following facts apply here:
-
-- `co('a)` is a subtype of `co('b) when `'a` is a subtype of `'b`
-- `ct('a)` is a subtype of `ct('b) when `'b` is a subtype of `'a`
-- `in('a)` is a subtype of `in('b) when `'a` is equal to `'b`
-- `bi('a)` is a subtype of `bi('b) always
-
-That altogether induce the following rules of subtyping in Sophia:
-
-- A function type `(Args1) => Ret1` is a subtype of `(Args2) => Ret2` when `Ret1`
-is a subtype of `Ret2` and each argument type from `Args2` is a subtype of its
-counterpart in `Args1`.
-
-- A list type `list(A)` is a subtype of `list(B)` if `A` is a subtype of `B`.
-
-- An option type `option(A)` is a subtype of `option(B)` if `A` is a subtype of `B`.
-
-- A map type `map(A1, A2)` is a subtype of `map(B1, B2)` if `A1` is a subtype
-of `B1`, and `A2` is a subtype of `B2`.
-
-- An oracle type `oracle(A1, A2)` is a subtype of `oracle(B1, B2)` if `B1` is
-a subtype of `A1`, and `A2` is a subtype of `B2`.
-
-- An oracle_query type `oracle_query(A1, A2)` is a subtype of `oracle_query(B1, B2)`
-if `A1` is a subtype of `B1`, and `A2` is a subtype of `B2`.
-
-- A user-defined datatype `t(Args1)` is a subtype of `t(Args2)`
-
-- When a user-defined type `t('a)` is covariant in `'a`, then `t(A)` is a
-subtype of `t(B)` when `A` is a subtype of `B`.
-
-- When a user-defined type `t('a)` is contravariant in `'a`, then `t(A)` is a
-subtype of `t(B)` when `B` is a subtype of `A`.
-
-- When a user-defined type `t('a)` is binvariant in `'a`, then `t(A)` is a
-subtype of `t(B)` when either `A` is a subtype of `B` or when `B` is a subtype
-of `A`.
-
-- When a user-defined type `t('a)` is invariant in `'a`, then `t(A)` can never be
-a subtype of `t(B)`.
 
 ## Mutable state
 
@@ -503,28 +354,29 @@ namespace C =
 ## Types
 Sophia has the following types:
 
-| Type                 | Description                                                                                 | Example                                                      |
-|----------------------|---------------------------------------------------------------------------------------------|--------------------------------------------------------------|
-| int                  | A 2-complement integer                                                                      | ```-1```                                                     |
-| address              | æternity address, 32 bytes                                                                 | ```Call.origin```                                            |
-| bool                 | A Boolean                                                                                   | ```true```                                                   |
-| bits                 | A bit field                                                                                 | ```Bits.none```                                              |
-| bytes(n)             | A byte array with `n` bytes                                                                 | ```#fedcba9876543210```                                      |
-| string               | An array of bytes                                                                           | ```"Foo"```                                                  |
-| list                 | A homogeneous immutable singly linked list.                                                 | ```[1, 2, 3]```                                              |
-| ('a, 'b) => 'c       | A function. Parentheses can be skipped if there is only one argument                        | ```(x : int, y : int) => x + y```                            |
-| tuple                | An ordered heterogeneous array                                                              | ```(42, "Foo", true)```                                      |
-| record               | An immutable key value store with fixed key names and typed values                          | ``` record balance = { owner: address, value: int } ```      |
-| map                  | An immutable key value store with dynamic mapping of keys of one type to values of one type | ```type accounts = map(string, address)```                   |
-| option('a)           | An optional value either None or Some('a)                                                   | ```Some(42)```                                               |
-| state                | A user defined type holding the contract state                                              | ```record state = { owner: address, magic_key: bytes(4) }``` |
-| event                | An append only list of blockchain events (or log entries)                                   | ```datatype event = EventX(indexed int, string)```           |
-| hash                 | A 32-byte hash - equivalent to `bytes(32)`                                                  |                                                              |
-| signature            | A signature - equivalent to `bytes(64)`                                                     |                                                              |
-| Chain.ttl            | Time-to-live (fixed height or relative to current block)                                    | ```FixedTTL(1050)``` ```RelativeTTL(50)```                   |
-| oracle('a, 'b)       | And oracle answering questions of type 'a with answers of type 'b                           | ```Oracle.register(acct, qfee, ttl)```                       |
-| oracle_query('a, 'b) | A specific oracle query                                                                     | ```Oracle.query(o, q, qfee, qttl, rttl)```                   |
-| contract             | A user defined, typed, contract address                                                     | ```function call_remote(r : RemoteContract) = r.fun()```     |
+| Type                 | Description                                                                                 | Example                                                                       |
+|----------------------|---------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------|
+| int                  | A 2-complement integer                                                                      | ```-1```                                                                      |
+| char                 | A single character                                                                          | ```'c'```                                                                     |
+| address              | æternity address, 32 bytes                                                                  | ```Call.origin``` ```ak_2gx9MEFxKvY9vMG5YnqnXWv1hCsX7rgnfvBLJS4aQurustR1rt``` |
+| bool                 | A Boolean                                                                                   | ```true```                                                                    |
+| bits                 | A bit field                                                                                 | ```Bits.none```                                                               |
+| bytes(n)             | A byte array with `n` bytes                                                                 | ```#fedcba9876543210```                                                       |
+| string               | An array of bytes                                                                           | ```"Foo"```                                                                   |
+| list                 | A homogeneous immutable singly linked list.                                                 | ```[1, 2, 3]```                                                               |
+| ('a, 'b) => 'c       | A function. Parentheses can be skipped if there is only one argument                        | ```(x : int, y : int) => x + y```                                             |
+| tuple                | An ordered heterogeneous array                                                              | ```(42, "Foo", true)```                                                       |
+| record               | An immutable key value store with fixed key names and typed values                          | ``` record balance = { owner: address, value: int } ```                       |
+| map                  | An immutable key value store with dynamic mapping of keys of one type to values of one type | ```type accounts = map(string, address)```                                    |
+| option('a)           | An optional value either None or Some('a)                                                   | ```Some(42)```                                                                |
+| state                | A user defined type holding the contract state                                              | ```record state = { owner: address, magic_key: bytes(4) }```                  |
+| event                | An append only list of blockchain events (or log entries)                                   | ```datatype event = EventX(indexed int, string)```                            |
+| hash                 | A 32-byte hash - equivalent to `bytes(32)`                                                  |                                                                               |
+| signature            | A signature - equivalent to `bytes(64)`                                                     |                                                                               |
+| Chain.ttl            | Time-to-live (fixed height or relative to current block)                                    | ```FixedTTL(1050)``` ```RelativeTTL(50)```                                    |
+| oracle('a, 'b)       | And oracle answering questions of type 'a with answers of type 'b                           | ```Oracle.register(acct, qfee, ttl)```                                        |
+| oracle_query('a, 'b) | A specific oracle query                                                                     | ```Oracle.query(o, q, qfee, qttl, rttl)```                                    |
+| contract             | A user defined, typed, contract address                                                     | ```function call_remote(r : RemoteContract) = r.fun()```                      |
 
 ## Literals
 | Type                 | Constant/Literal example(s)                                                                                                         |
@@ -650,6 +502,59 @@ function
 
 Guards cannot be stateful even when used inside a stateful function.
 
+## Comparable types
+
+Only certain types are allowed to be compared by equality (`==`, `!=`) and
+inequality (`<`, `>`, `=<`, `>=`). For instance, while it is legal to compare
+integers, comparing functions would lead to an error:
+
+```
+function f() = 
+  f == f  // type error
+```
+
+The rules apply as follows:
+
+- All types that are comparable by inequality are also comparable by equality.
+- The builtin types `bool`, `int`, `char`, `bits`, `bytes`, `string`, `unit`,
+  `hash`, `address` and `signature` are comparable by inequality (and thus by
+  equality).
+- The composite types `list`, `option`, and tuples are comparable by
+  equality/inequality if their type parameters are comparable by
+  equality/inequality.
+- The composite types `map`, `oracle`, and `oracle_query` are comparable by
+  equality if their type parameters are comparable by equality.
+- User-defined records and datatypes are comparable by equality if their type
+  parameters are comparable by equality.
+- Smart contracts are comparable by equality.
+- User-declared type variables are comparable according to the [type
+  constraints](#type-constraints) given in the function signature.
+
+In all other cases the types are not comparable.
+
+### Type constraints
+
+Polymorphic types are not declared as comparable by default. If the user
+specifies the type signature for a function, they need to manually declare type
+constraints in order to allow the variables to be compared. This can only be
+done if the type declaration is separated from the function definition. The
+constraints have to be prepended to the type declaration and separated with a
+semicolon:
+
+```
+
+function eq(x : 'a, y : 'a) = x == y  // Type error, 'a is not comparable
+
+function
+  eq : 'a is eq ; ('a, 'a) => bool
+  eq(x, y) = x == y                   // Compiles
+
+function eq(x, y) = x == y            // Compiles as the constraints are inferred
+```
+
+Currently only two constraints are allowed: `eq` for equality and `ord` for
+inequality. Declaring a type as `ord` automatically implies `eq`.
+
 ## Lists
 
 A Sophia list is a dynamically sized, homogenous, immutable, singly
@@ -1011,16 +916,6 @@ function require(b : bool, err : string) =
     if(!b) abort(err)
 ```
 
-Aside from that, there is an almost equivalent function `exit`
-
-```sophia
-exit(reason : string) : 'a
-```
-
-Just like `abort`, it breaks the execution with the given reason. The difference
-however is in the gas consumption — while `abort` returns unused gas, a call to
-`exit` burns it all.
-
 ## Delegation signature
 
 Some chain operations (`Oracle.<operation>` and `AENS.<operation>`) have an

docs/sophia_stdlib.md

@@ -812,8 +812,8 @@ Registers new oracle answering questions of type `'a` with answers of type `'b`.
   private key of the account, proving you have the private key of the oracle to be. If the
   address is the same as the contract `sign` is ignored and can be left out entirely.
 * The `qfee` is the minimum query fee to be paid by a user when asking a question of the oracle.
-* The `ttl` is the Time To Live for the oracle in key blocks, either relative to the current
-  key block height (`RelativeTTL(delta)`) or a fixed key block height (`FixedTTL(height)`).
+* The `ttl` is the Time To Live for the oracle, either relative to the current
+  height (`RelativeTTL(delta)`) or a fixed height (`FixedTTL(height)`).
 * The type `'a` is the type of the question to ask.
 * The type `'b` is the type of the oracle answers.
 

priv/stdlib/List.aes

@@ -29,9 +29,11 @@ namespace List =
     []   => abort("drop_last_unsafe: list empty")
 
 
-  function contains(e : 'a, l : list('a)) = switch(l)
-    []   => false
-    h::t => h == e || contains(e, t)
+  function
+    contains : 'a is eq; ('a, list('a)) => bool
+    contains(e, l) = switch(l)
+      []   => false
+      h::t => h == e || contains(e, t)
 
 /** Finds first element of `l` fulfilling predicate `p` as `Some` or `None`
  * if no such element exists.

priv/stdlib/Option.aes

@@ -30,7 +30,9 @@ namespace Option =
     None    => abort(err)
     Some(x) => x
 
-  function contains(e : 'a, o : option('a)) = o == Some(e)
+  function
+    contains : 'a is eq; ('a, option('a)) => bool
+    contains(e, o) = o == Some(e)
 
   function on_elem(o : option('a), f : 'a => unit) : unit = match((), f, o)
 

priv/stdlib/String.aes

@@ -90,6 +90,7 @@ namespace String =
           Some(ix)
 
   private function
+    is_prefix : (list(char), list(char)) => option(list(char))
     is_prefix([], ys) = Some(ys)
     is_prefix(_, [])  = None
     is_prefix(x :: xs, y :: ys) =
@@ -98,10 +99,10 @@ namespace String =
 
   private function
     to_int_([], _, x, _) = Some(x)
-    to_int_(i :: is, value, x, b) =
+    to_int_(i :: ints, value, x, b) =
       switch(value(i))
         None => None
-        Some(n) => to_int_(is, value, x * b + n, b)
+        Some(i) => to_int_(ints, value, x * b + i, b)
 
   private function ch_to_int_10(ch) =
     let c = Char.to_int(ch)

rebar.config

@@ -2,10 +2,11 @@
 
 {erl_opts, [debug_info]}.
 
-{deps, [ {aebytecode, {git, "https://github.com/aeternity/aebytecode.git", {tag, "v3.1.1"}}}
+{deps, [ {aebytecode, {git, "https://github.com/aeternity/aebytecode.git", {ref,"0699f35"}}}
        , {getopt, "1.0.1"}
        , {eblake2, "1.0.0"}
-       , {jsx, {git, "https://github.com/talentdeficit/jsx.git", {tag, "2.8.0"}}}
+       , {jsx, {git, "https://github.com/talentdeficit/jsx.git",
+                     {tag, "2.8.0"}}}
        ]}.
 
 {dialyzer, [
@@ -14,7 +15,7 @@
             {base_plt_apps, [erts, kernel, stdlib, crypto, mnesia]}
            ]}.
 
-{relx, [{release, {aesophia, "7.0.0"},
+{relx, [{release, {aesophia, "6.1.0"},
          [aesophia, aebytecode, getopt]},
 
         {dev_mode, true},

rebar.lock

@@ -1,11 +1,11 @@
-{"1.2.0",
+{"1.1.0",
 [{<<"aebytecode">>,
   {git,"https://github.com/aeternity/aebytecode.git",
-       {ref,"8269dbd71e9011921c60141636f1baa270a0e784"}},
+       {ref,"0699f35b0398bac6cd4468da654d608375bd853d"}},
   0},
  {<<"aeserialization">>,
   {git,"https://github.com/aeternity/aeserialization.git",
-       {ref,"eb68fe331bd476910394966b7f5ede7a74d37e35"}},
+       {ref,"47aaa8f5434b365c50a35bfd1490340b19241991"}},
   1},
  {<<"base58">>,
   {git,"https://github.com/aeternity/erl-base58.git",
@@ -14,7 +14,7 @@
  {<<"eblake2">>,{pkg,<<"eblake2">>,<<"1.0.0">>},0},
  {<<"enacl">>,
   {git,"https://github.com/aeternity/enacl.git",
-       {ref,"793ddb502f7fe081302e1c42227dca70b09f8e17"}},
+       {ref,"26180f42c0b3a450905d2efd8bc7fd5fd9cece75"}},
   2},
  {<<"getopt">>,{pkg,<<"getopt">>,<<"1.0.1">>},0},
  {<<"jsx">>,
@@ -24,8 +24,5 @@
 [
 {pkg_hash,[
  {<<"eblake2">>, <<"EC8AD20E438AAB3F2E8D5D118C366A0754219195F8A0F536587440F8F9BCF2EF">>},
- {<<"getopt">>, <<"C73A9FA687B217F2FF79F68A3B637711BB1936E712B521D8CE466B29CBF7808A">>}]},
-{pkg_hash_ext,[
- {<<"eblake2">>, <<"3C4D300A91845B25D501929A26AC2E6F7157480846FAB2347A4C11AE52E08A99">>},
- {<<"getopt">>, <<"53E1AB83B9CEB65C9672D3E7A35B8092E9BDC9B3EE80721471A161C10C59959C">>}]}
+ {<<"getopt">>, <<"C73A9FA687B217F2FF79F68A3B637711BB1936E712B521D8CE466B29CBF7808A">>}]}
 ].

src/aeso_aci.erl

@@ -83,7 +83,7 @@ from_typed_ast(Type, TypedAst) ->
         string -> do_render_aci_json(JArray)
     end.
 
-encode_contract(Contract = {Head, _, {con, _, Name}, _, _}) when ?IS_CONTRACT_HEAD(Head) ->
+encode_contract(Contract = {Head, _, {con, _, Name}, _}) when ?IS_CONTRACT_HEAD(Head) ->
     C0 = #{name => encode_name(Name)},
 
     Tdefs0 = [ encode_typedef(T) || T <- sort_decls(contract_types(Contract)) ],
@@ -341,12 +341,10 @@ stateful(false) -> "".
 
 %% #contract{Ann, Con, [Declarations]}.
 
-contract_funcs({C, _, _, _, Decls}) when ?IS_CONTRACT_HEAD(C) ->
+contract_funcs({C, _, _, Decls}) when ?IS_CONTRACT_HEAD(C); C == namespace ->
     [ D || D <- Decls, is_fun(D)].
 
-contract_types({namespace, _, _, Decls}) ->
-    [ D || D <- Decls, is_type(D) ];
-contract_types({C, _, _, _, Decls}) when ?IS_CONTRACT_HEAD(C) ->
+contract_types({C, _, _, Decls}) when ?IS_CONTRACT_HEAD(C); C == namespace ->
     [ D || D <- Decls, is_type(D) ].
 
 is_fun({letfun, _, _, _, _, _}) -> true;

src/aeso_ast_infer_types.erl

@@ -14,13 +14,8 @@
 
 -export([ infer/1
         , infer/2
-        , unfold_types_in_type/2
         , unfold_types_in_type/3
-        , switch_scope/2
         , pp_type/2
-        , lookup_env1/4
-        , name/1
-        , qname/1
         ]).
 
 -include("aeso_utils.hrl").
@@ -92,11 +87,10 @@
 -type byte_constraint() :: {is_bytes, utype()}
                          | {add_bytes, aeso_syntax:ann(), concat | split, utype(), utype(), utype()}.
 
--type aens_resolve_constraint() :: {aens_resolve_type, utype()}.
--type oracle_type_constraint() :: {oracle_type, aeso_syntax:ann(), utype()}.
+-type tvar_constraint() :: {is_eq, utype()}
+                         | {is_ord, utype()}.
 
--type constraint() :: named_argument_constraint() | field_constraint() | byte_constraint()
-                    | aens_resolve_constraint() | oracle_type_constraint().
+-type constraint() :: named_argument_constraint() | field_constraint() | byte_constraint() | tvar_constraint().
 
 -record(field_info,
     { ann      :: aeso_syntax:ann()
@@ -122,8 +116,6 @@
 
 -type type_constraints() :: none | bytes_concat | bytes_split | address_to_contract | bytecode_hash.
 
--type variance() :: invariant | covariant | contravariant | bivariant.
-
 -type fun_info()  :: {aeso_syntax:ann(), typesig() | type()}.
 -type type_info() :: {aeso_syntax:ann(), typedef()}.
 -type var_info()  :: {aeso_syntax:ann(), utype()}.
@@ -145,13 +137,11 @@
     , vars             = []                 :: [{name(), var_info()}]
     , typevars         = unrestricted       :: unrestricted | [name()]
     , fields           = #{}                :: #{ name() => [field_info()] }    %% fields are global
-    , contract_parents = #{}                :: #{ name() => [name()] }
     , namespace        = []                 :: qname()
     , used_namespaces  = []                 :: used_namespaces()
     , in_pattern       = false              :: boolean()
     , in_guard         = false              :: boolean()
     , stateful         = false              :: boolean()
-    , unify_throws     = true               :: boolean()
     , current_function = none               :: none | aeso_syntax:id()
     , what             = top                :: top | namespace | contract | contract_interface
     }).
@@ -164,10 +154,6 @@
 
 %% -- Environment manipulation -----------------------------------------------
 
--spec switch_scope(qname(), env()) -> env().
-switch_scope(Scope, Env) ->
-    Env#env{namespace = Scope}.
-
 -spec push_scope(namespace | contract, aeso_syntax:con(), env()) -> env().
 push_scope(Kind, Con, Env) ->
     Ann  = aeso_syntax:get_ann(Con),
@@ -297,7 +283,7 @@ contract_call_type({fun_t, Ann, [], Args, Ret}) ->
      Args, {if_t, Ann, Id("protected"), {app_t, Ann, {id, Ann, "option"}, [Ret]}, Ret}}.
 
 -spec bind_contract(aeso_syntax:decl(), env()) -> env().
-bind_contract({Contract, Ann, Id, _Impls, Contents}, Env)
+bind_contract({Contract, Ann, Id, Contents}, Env)
   when ?IS_CONTRACT_HEAD(Contract) ->
     Key    = name(Id),
     Sys    = [{origin, system}],
@@ -412,7 +398,7 @@ lookup_env(Env, Kind, Ann, Name) ->
             end
     end.
 
--spec lookup_env1(env(), type | term, aeso_syntax:ann(), qname()) -> false | {qname(), fun_info() | type_info()}.
+-spec lookup_env1(env(), type | term, aeso_syntax:ann(), qname()) -> false | {qname(), fun_info()}.
 lookup_env1(#env{ namespace = Current, used_namespaces = UsedNamespaces, scopes = Scopes }, Kind, Ann, QName) ->
     Qual = lists:droplast(QName),
     Name = lists:last(QName),
@@ -552,9 +538,8 @@ global_env() ->
                      %% TTL constructors
                      {"RelativeTTL", Fun1(Int, TTL)},
                      {"FixedTTL",    Fun1(Int, TTL)},
-                     %% Abort/exit
+                     %% Abort
                      {"abort", Fun1(String, A)},
-                     {"exit", Fun1(String, A)},
                      {"require", Fun([Bool, String], Unit)}])
         , types = MkDefs(
                     [{"int", 0}, {"bool", 0}, {"char", 0}, {"string", 0}, {"address", 0},
@@ -836,13 +821,11 @@ infer(Contracts, Options) ->
         ets_new(defined_contracts, [bag]),
         ets_new(type_vars, [set]),
         ets_new(warnings, [bag]),
-        ets_new(type_vars_variance, [set]),
-        %% Set the variance for builtin types
-        ets_insert(type_vars_variance, {"list", [covariant]}),
-        ets_insert(type_vars_variance, {"option", [covariant]}),
-        ets_insert(type_vars_variance, {"map", [covariant, covariant]}),
-        ets_insert(type_vars_variance, {"oracle", [contravariant, covariant]}),
-        ets_insert(type_vars_variance, {"oracle_query", [covariant, covariant]}),
+
+        %% Set the constraints for the builtin types
+        ets_new(ord_constraint_types, [set]),
+        OrdTypes = [ {"int"}, {"bool"}, {"bits"}, {"char"}, {"string"}, {"list"}, {"option"}, {"address"} ],
+        ets_insert(ord_constraint_types, OrdTypes),
 
         when_warning(warn_unused_functions, fun() -> create_unused_functions() end),
         check_modifiers(Env, Contracts),
@@ -871,12 +854,9 @@ infer(Contracts, Options) ->
 -spec infer1(env(), [aeso_syntax:decl()], [aeso_syntax:decl()], list(option())) ->
     {env(), [aeso_syntax:decl()]}.
 infer1(Env, [], Acc, _Options) -> {Env, lists:reverse(Acc)};
-infer1(Env0, [{Contract, Ann, ConName, Impls, Code} | Rest], Acc, Options)
+infer1(Env, [{Contract, Ann, ConName, Code} | Rest], Acc, Options)
   when ?IS_CONTRACT_HEAD(Contract) ->
     %% do type inference on each contract independently.
-    Env = Env0#env{ contract_parents = maps:put(name(ConName),
-                                                [name(Impl) || Impl <- Impls],
-                                                Env0#env.contract_parents) },
     check_scope_name_clash(Env, contract, ConName),
     What = case Contract of
                contract_main -> contract;
@@ -888,8 +868,7 @@ infer1(Env0, [{Contract, Ann, ConName, Impls, Code} | Rest], Acc, Options)
         contract_interface -> ok
     end,
     {Env1, Code1} = infer_contract_top(push_scope(contract, ConName, Env), What, Code, Options),
-    Contract1 = {Contract, Ann, ConName, Impls, Code1},
-    check_implemented_interfaces(Env1, Contract1, Acc),
+    Contract1 = {Contract, Ann, ConName, Code1},
     Env2 = pop_scope(Env1),
     Env3 = bind_contract(Contract1, Env2),
     infer1(Env3, Rest, [Contract1 | Acc], Options);
@@ -909,66 +888,17 @@ infer1(Env, [{pragma, _, _} | Rest], Acc, Options) ->
     %% Pragmas are checked in check_modifiers
     infer1(Env, Rest, Acc, Options).
 
-check_implemented_interfaces(Env, {_Contract, _Ann, ConName, Impls, Code}, DefinedContracts) ->
-    create_type_errors(),
-    AllInterfaces = [{name(IName), I} || I = {contract_interface, _, IName, _, _} <- DefinedContracts],
-    ImplsNames = lists:map(fun name/1, Impls),
-
-    %% All implemented intrefaces should already be defined
-    lists:foreach(fun(Impl) -> case proplists:get_value(name(Impl), AllInterfaces) of
-                                   undefined -> type_error({referencing_undefined_interface, Impl});
-                                   _         -> ok
-                               end
-                  end, Impls),
-
-    ImplementedInterfaces = [I || I <- [proplists:get_value(Name, AllInterfaces) || Name <- ImplsNames],
-                                    I /= undefined],
-    Funs = [ Fun || Fun <- Code,
-                    element(1, Fun) == letfun orelse element(1, Fun) == fun_decl ],
-    check_implemented_interfaces1(Env, ImplementedInterfaces, ConName, Funs, AllInterfaces),
-    destroy_and_report_type_errors(Env).
-
-%% Recursively check that all directly and indirectly referenced interfaces are implemented
-check_implemented_interfaces1(_, [], _, _, _) ->
-    ok;
-check_implemented_interfaces1(Env, [{contract_interface, _, IName, _, Decls} | Interfaces],
-                              ConId, Impls, AllInterfaces) ->
-    Unmatched = match_impls(Env, Decls, ConId, name(IName), Impls),
-    check_implemented_interfaces1(Env, Interfaces, ConId, Unmatched, AllInterfaces).
-
-%% Match the functions of the contract with the interfaces functions, and return unmatched functions
-match_impls(_, [], _, _, Impls) ->
-    Impls;
-match_impls(Env, [{fun_decl, _, {id, _, FunName}, FunType = {fun_t, _, _, ArgsTypes, RetDecl}} | Decls], ConId, IName, Impls) ->
-    Match = fun({letfun, _, {id, _, FName}, Args, RetFun, _}) when FName == FunName ->
-                    length(ArgsTypes) == length(Args) andalso
-                    unify(Env#env{unify_throws = false}, RetDecl, RetFun, unknown) andalso
-                    lists:all(fun({T1, {typed, _, _, T2}}) -> unify(Env#env{unify_throws = false}, T1, T2, unknown) end,
-                              lists:zip(ArgsTypes, Args));
-               ({fun_decl, _, {id, _, FName}, FunT}) when FName == FunName ->
-                    unify(Env#env{unify_throws = false}, FunT, FunType, unknown);
-               (_) -> false
-            end,
-    UnmatchedImpls = case lists:search(Match, Impls) of
-                         {value, V} ->
-                             lists:delete(V, Impls);
-                         false ->
-                             type_error({unimplemented_interface_function, ConId, IName, FunName}),
-                             Impls
-                     end,
-    match_impls(Env, Decls, ConId, IName, UnmatchedImpls).
-
 %% Asserts that the main contract is somehow defined.
 identify_main_contract(Contracts, Options) ->
-    Children   = [C || C = {contract_child, _, _, _, _} <- Contracts],
-    Mains      = [C || C = {contract_main, _, _, _, _} <- Contracts],
+    Children   = [C || C = {contract_child, _, _, _} <- Contracts],
+    Mains      = [C || C = {contract_main, _, _, _} <- Contracts],
     case Mains of
         [] -> case Children of
                   [] -> type_error(
                           {main_contract_undefined,
                            [{file, File} || {src_file, File} <- Options]});
-                  [{contract_child, Ann, Con, Impls, Body}] ->
-                      (Contracts -- Children) ++ [{contract_main, Ann, Con, Impls, Body}];
+                  [{contract_child, Ann, Con, Body}] ->
+                      (Contracts -- Children) ++ [{contract_main, Ann, Con, Body}];
                   [H|_] -> type_error({ambiguous_main_contract,
                                        aeso_syntax:get_ann(H)})
               end;
@@ -1027,9 +957,6 @@ infer_contract(Env0, What, Defs0, Options) ->
             contract           -> bind_state(Env1)   %% bind state and put
         end,
     {ProtoSigs, Decls} = lists:unzip([ check_fundecl(Env1, Decl) || Decl <- Get(prototype, Defs) ]),
-    [ type_error({missing_definition, Id}) || {fun_decl, _, Id, _} <- Decls,
-                                              What =:= contract,
-                                              get_option(no_code, false) =:= false ],
     Env3      = bind_funs(ProtoSigs, Env2),
     Functions = Get(function, Defs),
     %% Check for duplicates in Functions (we turn it into a map below)
@@ -1044,10 +971,8 @@ infer_contract(Env0, What, Defs0, Options) ->
     {Env4, Defs1} = check_sccs(Env3, FunMap, SCCs, []),
     %% Remove namespaces used in the current namespace
     Env5 = Env4#env{ used_namespaces = OldUsedNamespaces },
-    %% Check that `init` doesn't read or write the state and that `init` is not missing
-    check_state(Env4, Defs1),
-    %% Check that entrypoints have first-order arg types and return types
-    check_entrypoints(Defs1),
+    %% Check that `init` doesn't read or write the state
+    check_state_dependencies(Env4, Defs1),
     destroy_and_report_type_errors(Env4),
     %% Add inferred types of definitions
     {Env5, TypeDefs ++ Decls ++ Defs1}.
@@ -1114,7 +1039,6 @@ check_typedef_sccs(Env, TypeMap, [{acyclic, Name} | SCCs], Acc) ->
     case maps:get(Name, TypeMap, undefined) of
         undefined -> check_typedef_sccs(Env, TypeMap, SCCs, Acc);    %% Builtin type
         {type_def, Ann, D, Xs, Def0} ->
-            check_parameterizable(D, Xs),
             Def  = check_event(Env, Name, Ann, check_typedef(bind_tvars(Xs, Env), Def0)),
             Acc1 = [{type_def, Ann, D, Xs, Def} | Acc],
             Env1 = bind_type(Name, Ann, {Xs, Def}, Env),
@@ -1124,15 +1048,11 @@ check_typedef_sccs(Env, TypeMap, [{acyclic, Name} | SCCs], Acc) ->
                     type_error({empty_record_definition, Ann, Name}),
                     check_typedef_sccs(Env1, TypeMap, SCCs, Acc1);
                 {record_t, Fields} ->
-                    ets_insert(type_vars_variance, {Env#env.namespace ++ qname(D),
-                                                    infer_type_vars_variance(Xs, Fields)}),
                     %% check_type to get qualified name
                     RecTy = check_type(Env1, app_t(Ann, D, Xs)),
                     Env2 = check_fields(Env1, TypeMap, RecTy, Fields),
                     check_typedef_sccs(Env2, TypeMap, SCCs, Acc1);
                 {variant_t, Cons} ->
-                    ets_insert(type_vars_variance, {Env#env.namespace ++ qname(D),
-                                                    infer_type_vars_variance(Xs, Cons)}),
                     Target   = check_type(Env1, app_t(Ann, D, Xs)),
                     ConType  = fun([]) -> Target; (Args) -> {type_sig, Ann, none, [], Args, Target} end,
                     ConTypes = [ begin
@@ -1158,48 +1078,6 @@ check_typedef(Env, {variant_t, Cons}) ->
     {variant_t, [ {constr_t, Ann, Con, [ check_type(Env, Arg) || Arg <- Args ]}
                 || {constr_t, Ann, Con, Args} <- Cons ]}.
 
-infer_type_vars_variance(TypeParams, Cons) ->
-    % args from all type constructors
-    FlatArgs = lists:flatten([Args || {constr_t, _, _, Args} <- Cons]) ++ [Type || {field_t, _, _, Type} <- Cons],
-
-    Vs = lists:flatten([infer_type_vars_variance(Arg) || Arg <- FlatArgs]),
-    lists:map(fun({tvar, _, TVar}) ->
-                      S = sets:from_list([Variance || {TV, Variance} <- Vs, TV == TVar]),
-                      IsCovariant     = sets:is_element(covariant, S),
-                      IsContravariant = sets:is_element(contravariant, S),
-                      case {IsCovariant, IsContravariant} of
-                          {true,   true} -> invariant;
-                          {true,  false} -> covariant;
-                          {false,  true} -> contravariant;
-                          {false, false} -> bivariant
-                      end
-              end, TypeParams).
-
--spec infer_type_vars_variance(utype()) -> [{name(), variance()}].
-infer_type_vars_variance(Types)
-  when is_list(Types) ->
-    lists:flatten([infer_type_vars_variance(T) || T <- Types]);
-infer_type_vars_variance({app_t, _, Type, Args}) ->
-    Variances = case ets_lookup(type_vars_variance, qname(Type)) of
-                    [{_, Vs}] -> Vs;
-                    _ -> lists:duplicate(length(Args), covariant)
-                end,
-    TypeVarsVariance = [{TVar, Variance}
-                        || {{tvar, _, TVar}, Variance} <- lists:zip(Args, Variances)],
-    TypeVarsVariance;
-infer_type_vars_variance({tvar, _, TVar}) -> [{TVar, covariant}];
-infer_type_vars_variance({fun_t, _, [], Args, Res}) ->
-    ArgsVariance = infer_type_vars_variance(Args),
-    ResVariance = infer_type_vars_variance(Res),
-    FlippedArgsVariance = lists:map(fun({TVar, Variance}) -> {TVar, opposite_variance(Variance)} end, ArgsVariance),
-    FlippedArgsVariance ++ ResVariance;
-infer_type_vars_variance(_) -> [].
-
-opposite_variance(invariant) -> invariant;
-opposite_variance(covariant) -> contravariant;
-opposite_variance(contravariant) -> covariant;
-opposite_variance(bivariant) -> bivariant.
-
 check_usings(Env, []) ->
     Env;
 check_usings(Env = #env{ used_namespaces = UsedNamespaces }, [{using, Ann, Con, Alias, Parts} | Rest]) ->
@@ -1245,7 +1123,7 @@ check_modifiers(Env, Contracts) ->
     check_modifiers_(Env, Contracts),
     destroy_and_report_type_errors(Env).
 
-check_modifiers_(Env, [{Contract, _, Con, _Impls, Decls} | Rest])
+check_modifiers_(Env, [{Contract, _, Con, Decls} | Rest])
   when ?IS_CONTRACT_HEAD(Contract) ->
     IsInterface = Contract =:= contract_interface,
     check_modifiers1(contract, Decls),
@@ -1308,6 +1186,14 @@ check_modifiers1(What, Decl) when element(1, Decl) == letfun; element(1, Decl) =
     ok;
 check_modifiers1(_, _) -> ok.
 
+extract_typevars(Type) ->
+    case Type of
+        TVar = {tvar, _, _}    -> [TVar];
+        Tup when is_tuple(Tup) -> extract_typevars(tuple_to_list(Tup));
+        [H | T]                -> extract_typevars(H) ++ extract_typevars(T);
+        _                      -> []
+    end.
+
 -spec check_type(env(), aeso_syntax:type()) -> aeso_syntax:type().
 check_type(Env, T) ->
     check_type(Env, T, 0).
@@ -1350,6 +1236,15 @@ check_type(Env, Type = {fun_t, Ann, NamedArgs, Args, Ret}, Arity) ->
 check_type(_Env, Type = {uvar, _, _}, Arity) ->
     ensure_base_type(Type, Arity),
     Type;
+check_type(Env, {constrained_t, Ann, Constraints, Type}, Arity) ->
+    when_warning(warn_duplicated_constraints, fun() -> warn_duplicated_constraints(Constraints) end),
+    TVars = [ Name || {tvar, _, Name} <- extract_typevars(Type) ],
+    [ type_error({unused_constraint, C}) || C = {constraint, _, {tvar, _, Name}, _} <- Constraints,
+                                            not lists:member(Name, TVars) ],
+    [ type_error({unknown_tvar_constraint, C}) || C = {constraint, _, _, {id, _, Name}} <- Constraints,
+                                                  not lists:member(Name, ["eq", "ord"]) ],
+
+    {constrained_t, Ann, Constraints, check_type(Env, Type, Arity)};
 check_type(_Env, {args_t, Ann, Ts}, _) ->
     type_error({new_tuple_syntax, Ann, Ts}),
     {tuple_t, Ann, Ts}.
@@ -1370,13 +1265,6 @@ check_fields(Env, TypeMap, RecTy, [{field_t, Ann, Id, Type} | Fields]) ->
     Env1 = bind_field(name(Id), #field_info{ ann = Ann, kind = record, field_t = Type, record_t = RecTy }, Env),
     check_fields(Env1, TypeMap, RecTy, Fields).
 
-check_parameterizable({id, Ann, "event"}, [_ | _]) ->
-    type_error({parameterized_event, Ann});
-check_parameterizable({id, Ann, "state"}, [_ | _]) ->
-    type_error({parameterized_state, Ann});
-check_parameterizable(_Name, _Xs) ->
-    ok.
-
 check_event(Env, "event", Ann, Def) ->
     case Def of
         {variant_t, Cons} ->
@@ -1595,13 +1483,13 @@ app_t(Ann, Name, Args) -> {app_t, Ann, Name, Args}.
 lookup_name(Env, As, Name) ->
     lookup_name(Env, As, Name, []).
 
-lookup_name(Env = #env{ namespace = NS, current_function = CurFn }, As, Id, Options) ->
+lookup_name(Env = #env{ namespace = NS, current_function = {id, _, Fun} = CurFn }, As, Id, Options) ->
     case lookup_env(Env, term, As, qname(Id)) of
         false ->
             type_error({unbound_variable, Id}),
             {Id, fresh_uvar(As)};
         {QId, {_, Ty}} ->
-            when_warning(warn_unused_variables, fun() -> used_variable(NS, name(CurFn), QId) end),
+            when_warning(warn_unused_variables, fun() -> used_variable(NS, Fun, QId) end),
             when_warning(warn_unused_functions,
                          fun() -> register_function_call(NS ++ qname(CurFn), QId) end),
             Freshen = proplists:get_value(freshen, Options, false),
@@ -1639,52 +1527,8 @@ check_stateful_named_arg(#env{ stateful = false, current_function = Fun }, {id,
     end;
 check_stateful_named_arg(_, _, _) -> ok.
 
-check_entrypoints(Defs) ->
-    [ ensure_first_order_entrypoint(LetFun)
-      || LetFun <- Defs,
-         aeso_syntax:get_ann(entrypoint, LetFun, false),
-         get_option(allow_higher_order_entrypoints, false) =:= false ].
-
-ensure_first_order_entrypoint({letfun, Ann, Id = {id, _, Name}, Args, Ret, _}) ->
-    [ ensure_first_order(ArgType, {higher_order_entrypoint, AnnArg, Id, {argument, ArgId, ArgType}})
-      || {typed, AnnArg, ArgId, ArgType} <- Args ],
-    [ ensure_first_order(Ret, {higher_order_entrypoint, Ann, Id, {result, Ret}})
-      || Name /= "init" ],  %% init can return higher-order values, since they're written to the store
-                            %% rather than being returned.
-    ok.
-
-ensure_first_order(Type, Err) ->
-    is_first_order(Type) orelse type_error(Err).
-
-is_first_order({fun_t, _, _, _, _})    -> false;
-is_first_order(Ts) when is_list(Ts)    -> lists:all(fun is_first_order/1, Ts);
-is_first_order(Tup) when is_tuple(Tup) -> is_first_order(tuple_to_list(Tup));
-is_first_order(_)                      -> true.
-
-ensure_monomorphic(Type, Err) ->
-    is_monomorphic(Type) orelse type_error(Err).
-
-is_monomorphic({tvar, _, _})           -> false;
-is_monomorphic(Ts) when is_list(Ts)    -> lists:all(fun is_monomorphic/1, Ts);
-is_monomorphic(Tup) when is_tuple(Tup) -> is_monomorphic(tuple_to_list(Tup));
-is_monomorphic(_)                      -> true.
-
-check_state_init(Env) ->
-    Top = Env#env.namespace,
-    StateType = lookup_type(Env, {id, [{origin, system}], "state"}),
-    case unfold_types_in_type(Env, StateType) of
-        false  ->
-            ok;
-        {_, {_, {_, {alias_t, {tuple_t, _, []}}}}} ->  %% type state = ()
-            ok;
-        _ ->
-            #scope{ ann = AnnCon } = get_scope(Env, Top),
-            type_error({missing_init_function, {con, AnnCon, lists:last(Top)}})
-    end.
-
-%% Check that `init` doesn't read or write the state and that `init` is defined
-%% when the state type is not unit
-check_state(Env, Defs) ->
+%% Check that `init` doesn't read or write the state
+check_state_dependencies(Env, Defs) ->
     Top       = Env#env.namespace,
     GetState  = Top ++ ["state"],
     SetState  = Top ++ ["put"],
@@ -1693,7 +1537,7 @@ check_state(Env, Defs) ->
     Funs      = [ {Top ++ [Name], Fun} || Fun = {letfun, _, {id, _, Name}, _Args, _Type, _GuardedBodies} <- Defs ],
     Deps      = maps:from_list([{Name, UsedNames(Def)} || {Name, Def} <- Funs]),
     case maps:get(Init, Deps, false) of
-        false -> get_option(no_code, false) orelse check_state_init(Env);
+        false -> ok;    %% No init, so nothing to check
         _     ->
             [ type_error({init_depends_on_state, state, Chain})
               || Chain <- get_call_chains(Deps, Init, GetState) ],
@@ -1835,17 +1679,12 @@ infer_expr(Env, {app, Ann, Fun, Args0} = App) ->
             NewFun0 = infer_expr(Env, Fun),
             NewArgs = [infer_expr(Env, A) || A <- Args],
             ArgTypes = [T || {typed, _, _, T} <- NewArgs],
-            NewFun1 = {typed, _, FunName, FunType} = infer_var_args_fun(Env, NewFun0, NamedArgs1, ArgTypes),
+            NewFun1 = {typed, _, _, FunType} = infer_var_args_fun(Env, NewFun0, NamedArgs1, ArgTypes),
             When = {infer_app, Fun, NamedArgs1, Args, FunType, ArgTypes},
             GeneralResultType = fresh_uvar(Ann),
             ResultType = fresh_uvar(Ann),
             unify(Env, FunType, {fun_t, [], NamedArgsVar, ArgTypes, GeneralResultType}, When),
             when_warning(warn_negative_spend, fun() -> warn_potential_negative_spend(Ann, NewFun1, NewArgs) end),
-            [ add_constraint({aens_resolve_type, GeneralResultType})
-              || element(3, FunName) =:= ["AENS", "resolve"] ],
-            [ add_constraint({oracle_type, Ann, OType})
-              || OType <- [get_oracle_type(FunName, ArgTypes, GeneralResultType)],
-                 OType =/= false ],
             add_constraint(
               #dependent_type_constraint{ named_args_t = NamedArgsVar,
                                           named_args   = NamedArgs1,
@@ -2095,7 +1934,7 @@ infer_case(Env = #env{ namespace = NS, current_function = {id, _, Fun} }, Attrs,
         {guarded, Ann, NewGuards, NewBranch}
     end,
     NewGuardedBranches = lists:map(InferGuardedBranches, GuardedBranches),
-    unify(Env, ExprType, PatType, {case_pat, Pattern, PatType, ExprType}),
+    unify(Env, PatType, ExprType, {case_pat, Pattern, PatType, ExprType}),
     {'case', Attrs, NewPattern, NewGuardedBranches}.
 
 %% NewStmts = infer_block(Env, Attrs, Stmts, BlockType)
@@ -2130,10 +1969,16 @@ infer_infix({IntOp, As})
     Int = {id, As, "int"},
     {fun_t, As, [], [Int, Int], Int};
 infer_infix({RelOp, As})
-  when RelOp == '=='; RelOp == '!=';
-       RelOp == '<';  RelOp == '>';
+  when RelOp == '=='; RelOp == '!=' ->
+    T = fresh_uvar(As),
+    add_constraint({is_eq, T}),
+    Bool = {id, As, "bool"},
+    {fun_t, As, [], [T, T], Bool};
+infer_infix({RelOp, As})
+  when RelOp == '<';  RelOp == '>';
        RelOp == '<='; RelOp == '=<'; RelOp == '>=' ->
-    T = fresh_uvar(As),     %% allow any type here, check in the backend that we have comparison for it
+    T = fresh_uvar(As),
+    add_constraint({is_ord, T}),
     Bool = {id, As, "bool"},
     {fun_t, As, [], [T, T], Bool};
 infer_infix({'..', As}) ->
@@ -2204,7 +2049,7 @@ next_count() ->
 ets_tables() ->
     [options, type_vars, constraints, freshen_tvars, type_errors,
      defined_contracts, warnings, function_calls, all_functions,
-     type_vars_variance].
+     ord_constraint_types].
 
 clean_up_ets() ->
     [ catch ets_delete(Tab) || Tab <- ets_tables() ],
@@ -2371,14 +2216,11 @@ destroy_and_report_unsolved_constraints(Env) ->
                            ({add_bytes, _, _, _, _, _}) -> true;
                            (_)                          -> false
                         end, OtherCs3),
-    {AensResolveCs, OtherCs5} =
-        lists:partition(fun({aens_resolve_type, _}) -> true;
-                           (_)                      -> false
+    {TVarsCs, []} =
+        lists:partition(fun({is_eq, _})  -> true;
+                           ({is_ord, _}) -> true;
+                           (_)           -> false
                         end, OtherCs4),
-    {OracleTypeCs, []} =
-        lists:partition(fun({oracle_type, _, _}) -> true;
-                           (_)                   -> false
-                        end, OtherCs5),
 
     Unsolved = [ S || S <- [ solve_constraint(Env, dereference_deep(C)) || C <- NamedArgCs ],
                       S == unsolved ],
@@ -2396,20 +2238,10 @@ destroy_and_report_unsolved_constraints(Env) ->
     check_record_create_constraints(Env, CreateCs),
     check_is_contract_constraints(Env, ContractCs),
     check_bytes_constraints(Env, BytesCs),
-    check_aens_resolve_constraints(Env, AensResolveCs),
-    check_oracle_type_constraints(Env, OracleTypeCs),
+    check_tvars_constraints(Env, TVarsCs),
 
     destroy_constraints().
 
-get_oracle_type({qid, _, ["Oracle", "register"]},      _        , OType) -> OType;
-get_oracle_type({qid, _, ["Oracle", "query"]},        [OType| _], _    ) -> OType;
-get_oracle_type({qid, _, ["Oracle", "get_question"]}, [OType| _], _    ) -> OType;
-get_oracle_type({qid, _, ["Oracle", "get_answer"]},   [OType| _], _    ) -> OType;
-get_oracle_type({qid, _, ["Oracle", "check"]},        [OType| _], _    ) -> OType;
-get_oracle_type({qid, _, ["Oracle", "check_query"]},  [OType| _], _    ) -> OType;
-get_oracle_type({qid, _, ["Oracle", "respond"]},      [OType| _], _    ) -> OType;
-get_oracle_type(_Fun, _Args, _Ret) -> false.
-
 %% -- Named argument constraints --
 
 %% If false, a type error has been emitted, so it's safe to drop the constraint.
@@ -2536,31 +2368,32 @@ check_bytes_constraint(Env, {add_bytes, Ann, Fun, A0, B0, C0}) ->
         _ -> type_error({unsolved_bytes_constraint, Ann, Fun, A, B, C})
     end.
 
-check_aens_resolve_constraints(_Env, []) ->
-    ok;
-check_aens_resolve_constraints(Env, [{aens_resolve_type, Type} | Rest]) ->
-    Type1 = unfold_types_in_type(Env, instantiate(Type)),
-    {app_t, _, {id, _, "option"}, [Type2]} = Type1,
-    case Type2 of
-        {id, _, "string"} -> ok;
-        {id, _, "address"} -> ok;
-        {con, _, _} -> ok;
-        {app_t, _, {id, _, "oracle"}, [_, _]} -> ok;
-        {app_t, _, {id, _, "oracle_query"}, [_, _]} -> ok;
-        _ -> type_error({invalid_aens_resolve_type, aeso_syntax:get_ann(Type), Type2})
-    end,
-    check_aens_resolve_constraints(Env, Rest).
+%% -- Typevars constraints --
 
-check_oracle_type_constraints(_Env, []) ->
-    ok;
-check_oracle_type_constraints(Env, [{oracle_type, Ann, OType} | Rest]) ->
-    Type = unfold_types_in_type(Env, instantiate(OType)),
-    {app_t, _, {id, _, "oracle"}, [QType, RType]} = Type,
-    ensure_monomorphic(QType, {invalid_oracle_type, polymorphic,  query,    Ann, Type}),
-    ensure_monomorphic(RType, {invalid_oracle_type, polymorphic,  response, Ann, Type}),
-    ensure_first_order(QType, {invalid_oracle_type, higher_order, query,    Ann, Type}),
-    ensure_first_order(RType, {invalid_oracle_type, higher_order, response, Ann, Type}),
-    check_oracle_type_constraints(Env, Rest).
+check_tvars_constraints(Env, Constraints) ->
+    [ check_tvars_constraint(Env, C) || C <- Constraints ].
+
+check_tvars_constraint(Env, {is_eq, Type = {uvar, Ann, _}}) ->
+    Type1 = unfold_types_in_type(Env, instantiate(Type)),
+    type_is_eq(Type1) orelse type_error({type_not_eq, Ann, Type1});
+check_tvars_constraint(Env, {is_ord, Type = {uvar, Ann, _}}) ->
+    Type1 = unfold_types_in_type(Env, instantiate(Type)),
+    type_is_ord(Type1) orelse type_error({type_not_ord, Ann, Type1}).
+
+type_is_ord({app_t, _, Id, Ts}) -> type_is_ord(Id) andalso lists:all(fun type_is_ord/1, Ts);
+type_is_ord({tuple_t, _, Ts}) -> lists:all(fun type_is_ord/1, Ts);
+type_is_ord({bytes_t, _, _}) -> true;
+type_is_ord({constrained_t, _, Constraints, {tvar, _, _}}) -> lists:keyfind("ord", 3, Constraints) =/= false;
+type_is_ord({id, _, Id}) -> ets_lookup(ord_constraint_types, Id) =/= [];
+type_is_ord(_) -> false.
+
+type_is_eq({app_t, _, Id, Ts}) -> type_is_eq(Id) andalso lists:all(fun type_is_eq/1, Ts);
+type_is_eq({con, _, _}) -> true;
+type_is_eq({qcon, _, _}) -> true;
+type_is_eq({id, _, _}) -> true;
+type_is_eq({qid, _, _}) -> true;
+type_is_eq({constrained_t, _, Constraints, {tvar, _, _}}) -> lists:keyfind("eq", 3, Constraints) =/= false;
+type_is_eq(T) -> type_is_ord(T).
 
 %% -- Field constraints --
 
@@ -2789,11 +2622,9 @@ subst_tvars1(_Env, X) ->
 
 %% Unification
 
-unify(Env, A, B, When) -> unify0(Env, A, B, covariant, When).
-
-unify0(_, {id, _, "_"}, _, _Variance, _When) -> true;
-unify0(_, _, {id, _, "_"}, _Variance, _When) -> true;
-unify0(Env, A, B, Variance, When) ->
+unify(_, {id, _, "_"}, _, _When) -> true;
+unify(_, _, {id, _, "_"}, _When) -> true;
+unify(Env, A, B, When) ->
     Options =
         case When of    %% Improve source location for map_in_map_key errors
             {check_expr, E, _, _} -> [{ann, aeso_syntax:get_ann(E)}];
@@ -2801,128 +2632,102 @@ unify0(Env, A, B, Variance, When) ->
         end,
     A1 = dereference(unfold_types_in_type(Env, A, Options)),
     B1 = dereference(unfold_types_in_type(Env, B, Options)),
-    unify1(Env, A1, B1, Variance, When).
+    unify1(Env, A1, B1, When).
 
-unify1(_Env, {uvar, _, R}, {uvar, _, R}, _Variance, _When) ->
+unify1(_Env, {uvar, _, R}, {uvar, _, R}, _When) ->
     true;
-unify1(Env, {uvar, A, R}, T, _Variance, When) ->
+unify1(_Env, {uvar, A, R}, T, When) ->
     case occurs_check(R, T) of
         true ->
-            if
-                Env#env.unify_throws ->
-                    cannot_unify({uvar, A, R}, T, none, When);
-                true ->
-                    ok
-            end,
+            cannot_unify({uvar, A, R}, T, When),
             false;
         false ->
             ets_insert(type_vars, {R, T}),
             true
     end;
-unify1(Env, T, {uvar, A, R}, Variance, When) ->
-    unify1(Env, {uvar, A, R}, T, Variance, When);
-unify1(_Env, {tvar, _, X}, {tvar, _, X}, _Variance, _When) -> true; %% Rigid type variables
-unify1(Env, [A|B], [C|D], [V|Variances], When) ->
-    unify0(Env, A, C, V, When) andalso unify0(Env, B, D, Variances, When);
-unify1(Env, [A|B], [C|D], Variance, When) ->
-    unify0(Env, A, C, Variance, When) andalso unify0(Env, B, D, Variance, When);
-unify1(_Env, X, X, _Variance, _When) ->
+unify1(Env, T, {uvar, A, R}, When) ->
+    unify1(Env, {uvar, A, R}, T, When);
+unify1(Env, {constrained_t, _, Cs, UVar = {uvar, _, _}}, Type2, When) ->
+    [ add_constraint({is_ord, UVar}) || {id, _, "ord"} <- Cs ],
+    [ add_constraint({is_eq, UVar}) || {id, _, "eq"} <- Cs ],
+    unify1(Env, UVar, Type2, When);
+unify1(Env, Type1, UVar = {constrained_t, _, Cs, {uvar, _, _}}, When) ->
+    [ add_constraint({is_ord, UVar}) || {id, _, "ord"} <- Cs ],
+    [ add_constraint({is_eq, UVar}) || {id, _, "eq"} <- Cs ],
+    unify1(Env, Type1, UVar, When);
+unify1(_Env, {tvar, _, X}, {tvar, _, X}, _When) -> true; %% Rigid type variables
+unify1(_Env, {constrained_t, _, Cs, {tvar, _, X}}, {constrained_t, _, Cs, {tvar, _, X}}, _When) -> true;
+unify1(Env, [A|B], [C|D], When) ->
+    unify(Env, A, C, When) andalso unify(Env, B, D, When);
+unify1(_Env, X, X, _When) ->
     true;
-unify1(_Env, {id, _, Name}, {id, _, Name}, _Variance, _When) ->
+unify1(_Env, {id, _, Name}, {id, _, Name}, _When) ->
     true;
-unify1(Env, A = {con, _, NameA}, B = {con, _, NameB}, Variance, When) ->
-    case is_subtype(Env, NameA, NameB, Variance) of
-        true -> true;
-        false ->
-            if
-                Env#env.unify_throws ->
-                    IsSubtype = is_subtype(Env, NameA, NameB, contravariant) orelse
-                                is_subtype(Env, NameA, NameB, covariant),
-                    Cxt = case IsSubtype of
-                              true  -> Variance;
-                              false -> none
-                          end,
-                    cannot_unify(A, B, Cxt, When);
-                true ->
-                    ok
-            end,
-            false
-    end;
-unify1(_Env, {qid, _, Name}, {qid, _, Name}, _Variance, _When) ->
+unify1(_Env, {con, _, Name}, {con, _, Name}, _When) ->
     true;
-unify1(_Env, {qcon, _, Name}, {qcon, _, Name}, _Variance, _When) ->
+unify1(_Env, {qid, _, Name}, {qid, _, Name}, _When) ->
     true;
-unify1(_Env, {bytes_t, _, Len}, {bytes_t, _, Len}, _Variance, _When) ->
+unify1(_Env, {qcon, _, Name}, {qcon, _, Name}, _When) ->
     true;
-unify1(Env, {if_t, _, {id, _, Id}, Then1, Else1}, {if_t, _, {id, _, Id}, Then2, Else2}, Variance, When) ->
-    unify0(Env, Then1, Then2, Variance, When) andalso
-    unify0(Env, Else1, Else2, Variance, When);
+unify1(_Env, {bytes_t, _, Len}, {bytes_t, _, Len}, _When) ->
+    true;
+unify1(Env, {if_t, _, {id, _, Id}, Then1, Else1}, {if_t, _, {id, _, Id}, Then2, Else2}, When) ->
+    unify(Env, Then1, Then2, When) andalso
+    unify(Env, Else1, Else2, When);
 
-unify1(_Env, {fun_t, _, _, _, _}, {fun_t, _, _, var_args, _}, _Variance, When) ->
+unify1(_Env, {fun_t, _, _, _, _}, {fun_t, _, _, var_args, _}, When) ->
     type_error({unify_varargs, When});
-unify1(_Env, {fun_t, _, _, var_args, _}, {fun_t, _, _, _, _}, _Variance, When) ->
+unify1(_Env, {fun_t, _, _, var_args, _}, {fun_t, _, _, _, _}, When) ->
     type_error({unify_varargs, When});
-unify1(Env, {fun_t, _, Named1, Args1, Result1}, {fun_t, _, Named2, Args2, Result2}, Variance, When)
+unify1(Env, {fun_t, _, Named1, Args1, Result1}, {fun_t, _, Named2, Args2, Result2}, When)
   when length(Args1) == length(Args2) ->
-    unify0(Env, Named1, Named2, opposite_variance(Variance), When) andalso
-    unify0(Env, Args1, Args2, opposite_variance(Variance), When) andalso
-    unify0(Env, Result1, Result2, Variance, When);
-unify1(Env, {app_t, _, {Tag, _, F}, Args1}, {app_t, _, {Tag, _, F}, Args2}, Variance, When)
+    unify(Env, Named1, Named2, When) andalso
+    unify(Env, Args1, Args2, When) andalso unify(Env, Result1, Result2, When);
+unify1(Env, {app_t, _, {Tag, _, F}, Args1}, {app_t, _, {Tag, _, F}, Args2}, When)
   when length(Args1) == length(Args2), Tag == id orelse Tag == qid ->
-    Variances = case ets_lookup(type_vars_variance, F) of
-                    [{_, Vs}] ->
-                        case Variance of
-                            contravariant -> lists:map(fun opposite_variance/1, Vs);
-                            invariant     -> invariant;
-                            _             -> Vs
-                        end;
-                    _ -> invariant
-                end,
-    unify1(Env, Args1, Args2, Variances, When);
-unify1(Env, {tuple_t, _, As}, {tuple_t, _, Bs}, Variance, When)
+    unify(Env, Args1, Args2, When);
+unify1(Env, {tuple_t, _, As}, {tuple_t, _, Bs}, When)
   when length(As) == length(Bs) ->
-    unify0(Env, As, Bs, Variance, When);
-unify1(Env, {named_arg_t, _, Id1, Type1, _}, {named_arg_t, _, Id2, Type2, _}, Variance, When) ->
-    unify1(Env, Id1, Id2, Variance, {arg_name, Id1, Id2, When}),
-    unify1(Env, Type1, Type2, Variance, When);
+    unify(Env, As, Bs, When);
+unify1(Env, {named_arg_t, _, Id1, Type1, _}, {named_arg_t, _, Id2, Type2, _}, When) ->
+    unify1(Env, Id1, Id2, {arg_name, Id1, Id2, When}),
+    unify1(Env, Type1, Type2, When);
+unify1(Env, {constrained_t, _, Constraints, Type1 = {fun_t, _, _, _, _}}, Type2, When) ->
+    unify1(Env, constrain_tvars(Type1, Constraints), Type2, When);
+unify1(Env, Type1, {constrained_t, _, Constraints, Type2 = {fun_t, _, _, _, _}}, When) ->
+    unify1(Env, Type1, constrain_tvars(Type2, Constraints), When);
 %% The grammar is a bit inconsistent about whether types without
 %% arguments are represented as applications to an empty list of
 %% parameters or not. We therefore allow them to unify.
-unify1(Env, {app_t, _, T, []}, B, Variance, When) ->
-    unify0(Env, T, B, Variance, When);
-unify1(Env, A, {app_t, _, T, []}, Variance, When) ->
-    unify0(Env, A, T, Variance, When);
-unify1(Env, A, B, _Variance, When) ->
-    if
-        Env#env.unify_throws ->
-            cannot_unify(A, B, none, When);
-        true ->
-            ok
-    end,
+unify1(Env, {app_t, _, T, []}, B, When) ->
+    unify(Env, T, B, When);
+unify1(Env, A, {app_t, _, T, []}, When) ->
+    unify(Env, A, T, When);
+unify1(_Env, A, B, When) ->
+    cannot_unify(A, B, When),
     false.
 
-is_subtype(_Env, NameA, NameB, invariant) ->
-    NameA == NameB;
-is_subtype(Env, NameA, NameB, covariant) ->
-    is_subtype(Env, NameA, NameB);
-is_subtype(Env, NameA, NameB, contravariant) ->
-    is_subtype(Env, NameB, NameA);
-is_subtype(Env, NameA, NameB, bivariant) ->
-    is_subtype(Env, NameA, NameB) orelse is_subtype(Env, NameB, NameA).
-
-is_subtype(Env, Child, Base) ->
-    Parents = maps:get(Child, Env#env.contract_parents, []),
-    if
-        Child == Base ->
-            true;
-        Parents == [] ->
-            false;
-        true ->
-            case lists:member(Base, Parents) of
-                true -> true;
-                false -> lists:any(fun(Parent) -> is_subtype(Env, Parent, Base) end, Parents)
-            end
-    end.
+%% Propagate the constraints to their corresponding type vars
+-spec constrain_tvars(utype() | [utype()], [constraint()]) -> utype().
+constrain_tvars(Types, Constraints)
+  when is_list(Types) ->
+    [ constrain_tvars(Type, Constraints) || Type <- Types ];
+constrain_tvars({fun_t, Ann, NamedArgs, ArgsT, RetT}, Constraints) ->
+    ConstrainedArgsT = constrain_tvars(ArgsT, Constraints),
+    ConstrainedRetT = constrain_tvars(RetT, Constraints),
+    {fun_t, Ann, NamedArgs, ConstrainedArgsT, ConstrainedRetT};
+constrain_tvars({app_t, Ann, AppT, ArgsT}, Constraints) ->
+    ConstrainedAppT = constrain_tvars(AppT, Constraints),
+    ConstrainedArgsT = constrain_tvars(ArgsT, Constraints),
+    {app_t, Ann, ConstrainedAppT, ConstrainedArgsT};
+constrain_tvars({tuple_t, Ann, ElemsT}, Constraints) ->
+    ConstrainedElemsT = constrain_tvars(ElemsT, Constraints),
+    {tuple_t, Ann, ConstrainedElemsT};
+constrain_tvars(TVar = {tvar, Ann, NameT}, Constraints) ->
+    TVarConstraints = [ C || {constraint, _, {tvar, _, NameC}, C} <- Constraints, NameT == NameC ],
+    {constrained_t, Ann, TVarConstraints, TVar};
+constrain_tvars(Type, _) ->
+    Type.
 
 dereference(T = {uvar, _, R}) ->
     case ets_lookup(type_vars, R) of
@@ -2951,6 +2756,7 @@ occurs_check1(_, {con, _, _}) -> false;
 occurs_check1(_, {qid, _, _}) -> false;
 occurs_check1(_, {qcon, _, _}) -> false;
 occurs_check1(_, {tvar, _, _}) -> false;
+occurs_check1(_, {constrained_t, _, _, _}) -> false;
 occurs_check1(_, {bytes_t, _, _}) -> false;
 occurs_check1(R, {fun_t, _, Named, Args, Res}) ->
     occurs_check(R, [Res, Named | Args]);
@@ -3067,7 +2873,8 @@ all_warnings() ->
     , warn_unused_functions
     , warn_shadowing
     , warn_division_by_zero
-    , warn_negative_spend ].
+    , warn_negative_spend
+    , warn_duplicated_constraints ].
 
 when_warning(Warn, Do) ->
     case lists:member(Warn, all_warnings()) of
@@ -3204,10 +3011,23 @@ warn_potential_negative_spend(Ann, Fun, Args) ->
         _ -> ok
     end.
 
+%% Warnings (Duplicated tvar constraints)
+
+warn_duplicated_constraints(Constraints) ->
+    warn_duplicated_constraints([], Constraints).
+
+warn_duplicated_constraints(_, []) -> ok;
+warn_duplicated_constraints(UniqueConstraints, [Constraint = {constraint, _, {tvar, _, Name1}, {id, _, Constr1}}| Rest]) ->
+    case [ C || C = {constraint, _, {tvar, _, Name2}, {id, _, Constr2}} <- UniqueConstraints,
+                Name1 == Name2 andalso Constr1 == Constr2 ] of
+        []       -> warn_duplicated_constraints([Constraint | UniqueConstraints], Rest);
+        [Unique] -> ets_insert(warnings, {duplicated_constraint, Constraint, Unique})
+    end.
+
 %% Save unification failures for error messages.
 
-cannot_unify(A, B, Cxt, When) ->
-    type_error({cannot_unify, A, B, Cxt, When}).
+cannot_unify(A, B, When) ->
+    type_error({cannot_unify, A, B, When}).
 
 type_error(Err) ->
     ets_insert(type_errors, Err).
@@ -3276,12 +3096,8 @@ mk_error({fundecl_must_have_funtype, _Ann, Id, Type}) ->
                        "Entrypoints and functions must have functional types"
                        , [pp(Id), pp(instantiate(Type))]),
     mk_t_err(pos(Id), Msg);
-mk_error({cannot_unify, A, B, Cxt, When}) ->
-    VarianceContext = case Cxt of
-                          none -> "";
-                          _    -> io_lib:format(" in a ~p context", [Cxt])
-                      end,
-    Msg = io_lib:format("Cannot unify `~s` and `~s`" ++ VarianceContext,
+mk_error({cannot_unify, A, B, When}) ->
+    Msg = io_lib:format("Cannot unify `~s` and `~s`",
                         [pp(instantiate(A)), pp(instantiate(B))]),
     {Pos, Ctxt} = pp_when(When),
     mk_t_err(Pos, Msg, Ctxt);
@@ -3412,7 +3228,7 @@ mk_error({namespace, _Pos, {con, Pos, Name}, _Def}) ->
     Msg = io_lib:format("Nested namespaces are not allowed. Namespace `~s` is not defined at top level.",
                         [Name]),
     mk_t_err(pos(Pos), Msg);
-mk_error({Contract, _Pos, {con, Pos, Name}, _Impls, _Def}) when ?IS_CONTRACT_HEAD(Contract) ->
+mk_error({Contract, _Pos, {con, Pos, Name}, _Def}) when ?IS_CONTRACT_HEAD(Contract) ->
     Msg = io_lib:format("Nested contracts are not allowed. Contract `~s` is not defined at top level.",
                         [Name]),
     mk_t_err(pos(Pos), Msg);
@@ -3599,50 +3415,18 @@ mk_error({unknown_warning, Warning}) ->
 mk_error({empty_record_definition, Ann, Name}) ->
     Msg = io_lib:format("Empty record definitions are not allowed. Cannot define the record `~s`", [Name]),
     mk_t_err(pos(Ann), Msg);
-mk_error({unimplemented_interface_function, ConId, InterfaceName, FunName}) ->
-    Msg = io_lib:format("Unimplemented function `~s` from the interface `~s` in the contract `~s`", [FunName, InterfaceName, pp(ConId)]),
-    mk_t_err(pos(ConId), Msg);
-mk_error({referencing_undefined_interface, InterfaceId}) ->
-    Msg = io_lib:format("Trying to implement or extend an undefined interface `~s`", [pp(InterfaceId)]),
-    mk_t_err(pos(InterfaceId), Msg);
-mk_error({missing_definition, Id}) ->
-    Msg = io_lib:format("Missing definition of function `~s`", [name(Id)]),
-    mk_t_err(pos(Id), Msg);
-mk_error({parameterized_state, Ann}) ->
-    Msg = "The state type cannot be parameterized",
+mk_error({type_not_eq, Ann, Type}) ->
+    Msg = io_lib:format("Values of type `~s` are not comparable by equality", [pp_type("", Type)]),
     mk_t_err(pos(Ann), Msg);
-mk_error({parameterized_event, Ann}) ->
-    Msg = "The event type cannot be parameterized",
+mk_error({type_not_ord, Ann, Type}) ->
+    Msg = io_lib:format("Values of type `~s` are not comparable by inequality", [pp_type("", Type)]),
     mk_t_err(pos(Ann), Msg);
-mk_error({missing_init_function, Con}) ->
-    Msg = io_lib:format("Missing `init` function for the contract `~s`.", [name(Con)]),
-    Cxt = "The `init` function can only be omitted if the state type is `unit`",
-    mk_t_err(pos(Con), Msg, Cxt);
-mk_error({higher_order_entrypoint, Ann, {id, _, Name}, Thing}) ->
-    What = "higher-order (contains function types)",
-    ThingS = case Thing of
-                 {argument, X, T} -> io_lib:format("argument\n~s`\n", [pp_typed("  `", X, T)]);
-                 {result, T}      -> io_lib:format("return type\n~s`\n", [pp_type("  `", T)])
-             end,
-    Bad = case Thing of
-              {argument, _, _} -> io_lib:format("has a ~s type", [What]);
-              {result, _}      -> io_lib:format("is ~s", [What])
-          end,
-    Msg = io_lib:format("The ~sof entrypoint `~s` ~s",
-                        [ThingS, Name, Bad]),
+mk_error({unused_constraint, {constraint, Ann, {tvar, _, Name}, _}}) ->
+    Msg = io_lib:format("The type variable `~s` is constrained but never used", [Name]),
     mk_t_err(pos(Ann), Msg);
-mk_error({invalid_aens_resolve_type, Ann, T}) ->
-    Msg = io_lib:format("Invalid return type of `AENS.resolve`:\n"
-                        "~s`\n"
-                        "It must be a `string` or a pubkey type (`address`, `oracle`, etc)",
-                        [pp_type("  `", T)]),
+mk_error({unknown_tvar_constraint, {constraint, _, {tvar, _, TVar}, {id, Ann, C}}}) ->
+    Msg = io_lib:format("Unknown constraint `~s` used on the type variable `~s`", [C, TVar]),
     mk_t_err(pos(Ann), Msg);
-mk_error({invalid_oracle_type, Why, What, Ann, Type}) ->
-    WhyS = case Why of higher_order -> "higher-order (contain function types)";
-                       polymorphic  -> "polymorphic (contain type variables)" end,
-    Msg = io_lib:format("Invalid oracle type\n~s`", [pp_type("  `", Type)]),
-    Cxt = io_lib:format("The ~s type must not be ~s", [What, WhyS]),
-    mk_t_err(pos(Ann), Msg, Cxt);
 mk_error(Err) ->
     Msg = io_lib:format("Unknown error: ~p", [Err]),
     mk_t_err(pos(0, 0), Msg).
@@ -3674,6 +3458,10 @@ mk_warning({division_by_zero, Ann}) ->
 mk_warning({negative_spend, Ann}) ->
     Msg = io_lib:format("Negative spend.", []),
     aeso_warnings:new(pos(Ann), Msg);
+mk_warning({duplicated_constraint, {constraint, Ann, {tvar, _, Name}, _}, {constraint, AnnFirst, _, _}}) ->
+    Msg = io_lib:format("The constraint on the type variable `~s` is a duplication of the constraint at ~s",
+                        [Name, pp_loc(AnnFirst)]),
+    aeso_warnings:new(pos(Ann), Msg);
 mk_warning(Warn) ->
     Msg = io_lib:format("Unknown warning: ~p", [Warn]),
     aeso_warnings:new(Msg).
@@ -3898,6 +3686,8 @@ pp({uvar, _, Ref}) ->
     ["?u" | integer_to_list(erlang:phash2(Ref, 16384)) ];
 pp({tvar, _, Name}) ->
     Name;
+pp(T = {constrained_t, _, _, {tvar, _, _}}) ->
+    prettypr:format(aeso_pretty:type(T));
 pp({if_t, _, Id, Then, Else}) ->
     ["if(", pp([Id, Then, Else]), ")"];
 pp({tuple_t, _, []}) ->

src/aeso_ast_to_fcode.erl

@@ -242,7 +242,7 @@ builtins() ->
     MkName = fun(NS, Fun) ->
                 list_to_atom(string:to_lower(string:join(NS ++ [Fun], "_")))
              end,
-    Scopes = [{[],           [{"abort", 1}, {"require", 2}, {"exit", 1}]},
+    Scopes = [{[],           [{"abort", 1}, {"require", 2}]},
               {["Chain"],    [{"spend", 2}, {"balance", 1}, {"block_hash", 1}, {"coinbase", none},
                               {"timestamp", none}, {"block_height", none}, {"difficulty", none},
                               {"gas_limit", none}, {"bytecode_hash", 1}, {"create", variable}, {"clone", variable}]},
@@ -326,7 +326,7 @@ get_option(Opt, Env, Default) ->
 %% -- Compilation ------------------------------------------------------------
 
 -spec to_fcode(env(), aeso_syntax:ast()) -> {env(), fcode()}.
-to_fcode(Env, [{Contract, Attrs, {con, _, Name}, _Impls, Decls}|Rest])
+to_fcode(Env, [{Contract, Attrs, Con = {con, _, Name}, Decls}|Rest])
   when ?IS_CONTRACT_HEAD(Contract) ->
     case Contract =:= contract_interface of
         false ->
@@ -349,7 +349,7 @@ to_fcode(Env, [{Contract, Attrs, {con, _, Name}, _Impls, Decls}|Rest])
                           event_type    => EventType,
                           payable       => Payable,
                           functions     => add_init_function(
-                                             Env1,
+                                             Env1, Con, StateType,
                                              add_event_function(Env1, EventType, Funs)) },
             case Contract of
                 contract_main -> [] = Rest, {Env1, ConFcode};
@@ -362,6 +362,8 @@ to_fcode(Env, [{Contract, Attrs, {con, _, Name}, _Impls, Decls}|Rest])
             Env1 = decls_to_fcode(Env#{ context => {abstract_contract, Name} }, Decls),
             to_fcode(Env1, Rest)
     end;
+to_fcode(_Env, [NotMain = {NotMainHead, _ ,_ , _}]) when NotMainHead =/= contract_def ->
+    fcode_error({last_declaration_must_be_main_contract, NotMain});
 to_fcode(Env, [{namespace, _, {con, _, Con}, Decls} | Code]) ->
     Env1 = decls_to_fcode(Env#{ context => {namespace, Con} }, Decls),
     to_fcode(Env1, Code).
@@ -375,15 +377,22 @@ decls_to_fcode(Env, Decls) ->
                 end, Env1, Decls).
 
 -spec decl_to_fcode(env(), aeso_syntax:decl()) -> env().
+decl_to_fcode(Env = #{context := {contract_def, _}}, {fun_decl, _, Id, _}) ->
+    case is_no_code(Env) of
+        false -> fcode_error({missing_definition, Id});
+        true  -> Env
+    end;
 decl_to_fcode(Env, {fun_decl, _, _, _})  -> Env;
 decl_to_fcode(Env, {type_def, _Ann, Name, Args, Def}) ->
     typedef_to_fcode(Env, Name, Args, Def);
-decl_to_fcode(Env = #{ functions := Funs }, {letfun, Ann, {id, _, Name}, Args, Ret, [{guarded, _, [], Body}]}) ->
+decl_to_fcode(Env = #{ functions := Funs }, {letfun, Ann, Id = {id, _, Name}, Args, Ret, [{guarded, _, [], Body}]}) ->
     Attrs = get_attributes(Ann),
     FName = lookup_fun(Env, qname(Env, Name)),
     FArgs = args_to_fcode(Env, Args),
     FRet  = type_to_fcode(Env, Ret),
     FBody = expr_to_fcode(Env#{ vars => [X || {X, _} <- FArgs] }, Body),
+    [ ensure_first_order_entrypoint(Ann, Id, Args, Ret, FArgs, FRet)
+      || aeso_syntax:get_ann(entrypoint, Ann, false) ],
     Def   = #{ attrs  => Attrs,
                args   => FArgs,
                return => FRet,
@@ -392,7 +401,8 @@ decl_to_fcode(Env = #{ functions := Funs }, {letfun, Ann, {id, _, Name}, Args, R
     Env#{ functions := NewFuns }.
 
 -spec typedef_to_fcode(env(), aeso_syntax:id(), [aeso_syntax:tvar()], aeso_syntax:typedef()) -> env().
-typedef_to_fcode(Env, {id, _, Name}, Xs, Def) ->
+typedef_to_fcode(Env, Id = {id, _, Name}, Xs, Def) ->
+    check_state_and_event_types(Env, Id, Xs),
     Q = qname(Env, Name),
     FDef = fun(Args) when length(Args) == length(Xs) ->
                 Sub = maps:from_list(lists:zip([X || {tvar, _, X} <- Xs], Args)),
@@ -456,6 +466,14 @@ compute_state_layout(R, [H | T]) ->
 compute_state_layout(R, _) ->
     {R + 1, {reg, R}}.
 
+check_state_and_event_types(#{ context := {contract_def, _} }, Id, [_ | _]) ->
+    case Id of
+        {id, _, "state"} -> fcode_error({parameterized_state, Id});
+        {id, _, "event"} -> fcode_error({parameterized_event, Id});
+        _                -> ok
+    end;
+check_state_and_event_types(_, _, _) -> ok.
+
 -spec type_to_fcode(env(), aeso_syntax:type()) -> ftype().
 type_to_fcode(Env, Type) ->
     type_to_fcode(Env, #{}, Type).
@@ -473,8 +491,12 @@ type_to_fcode(Env, Sub, {record_t, Fields}) ->
     type_to_fcode(Env, Sub, {tuple_t, [], lists:map(FieldType, Fields)});
 type_to_fcode(_Env, _Sub, {bytes_t, _, N}) ->
     {bytes, N};
+type_to_fcode(_Env, _Sub, {tvar, Ann, "void"}) ->
+    fcode_error({found_void, Ann});
 type_to_fcode(_Env, Sub, {tvar, _, X}) ->
     maps:get(X, Sub, {tvar, X});
+type_to_fcode(Env, Sub, {constrained_t, _, _, TVar = {tvar, _, _}}) ->
+    type_to_fcode(Env, Sub, TVar);
 type_to_fcode(_Env, _Sub, {fun_t, Ann, _, var_args, _}) ->
     fcode_error({var_args_not_set, {id, Ann, "a very suspicious function"}});
 type_to_fcode(Env, Sub, {fun_t, _, Named, Args, Res}) ->
@@ -534,7 +556,7 @@ expr_to_fcode(_Env, _Type, {bytes,           _, B}) -> {lit, {bytes, B}};
 
 %% Variables
 expr_to_fcode(Env, _Type, {id, _, X})  -> resolve_var(Env, [X]);
-expr_to_fcode(Env, Type, {qid, _, X}) ->
+expr_to_fcode(Env, Type, {qid, Ann, X}) ->
     case resolve_var(Env, X) of
         {builtin_u, B, Ar} when B =:= oracle_query;
                                 B =:= oracle_get_question;
@@ -545,11 +567,13 @@ expr_to_fcode(Env, Type, {qid, _, X}) ->
                                 B =:= oracle_check_query ->
             OType = get_oracle_type(B, Type),
             {oracle, QType, RType} = type_to_fcode(Env, OType),
+            validate_oracle_type(Ann, OType, QType, RType),
             TypeArgs = [{lit, {typerep, QType}}, {lit, {typerep, RType}}],
             {builtin_u, B, Ar, TypeArgs};
         {builtin_u, B = aens_resolve, Ar} ->
             {fun_t, _, _, _, ResType} = Type,
             AensType = type_to_fcode(Env, ResType),
+            validate_aens_resolve_type(Ann, ResType, AensType),
             TypeArgs = [{lit, {typerep, AensType}}],
             {builtin_u, B, Ar, TypeArgs};
         {builtin_u, B = bytes_split, Ar} ->
@@ -802,6 +826,53 @@ get_oracle_type(oracle_check,        {fun_t, _, _, [OType | _], _}) -> OType;
 get_oracle_type(oracle_check_query,  {fun_t, _, _, [OType | _], _}) -> OType;
 get_oracle_type(oracle_respond,      {fun_t, _, _, [OType | _], _}) -> OType.
 
+validate_oracle_type(Ann, Type, QType, RType) ->
+    ensure_monomorphic(QType, {invalid_oracle_type, polymorphic,  query,    Ann, Type}),
+    ensure_monomorphic(RType, {invalid_oracle_type, polymorphic,  response, Ann, Type}),
+    ensure_first_order(QType, {invalid_oracle_type, higher_order, query,    Ann, Type}),
+    ensure_first_order(RType, {invalid_oracle_type, higher_order, response, Ann, Type}),
+    ok.
+
+validate_aens_resolve_type(Ann, {app_t, _, _, [Type]}, {variant, [[], [FType]]}) ->
+    case FType of
+        string         -> ok;
+        address        -> ok;
+        contract       -> ok;
+        {oracle, _, _} -> ok;
+        oracle_query   -> ok;
+        _              -> fcode_error({invalid_aens_resolve_type, Ann, Type})
+    end.
+
+ensure_first_order_entrypoint(Ann, Id = {id, _, Name}, Args, Ret, FArgs, FRet) ->
+    [ ensure_first_order(FT, {invalid_entrypoint, higher_order, Ann1, Id, {argument, X, T}})
+      || {{typed, Ann1, X, T}, {_, FT}} <- lists:zip(Args, FArgs) ],
+    [ ensure_first_order(FRet, {invalid_entrypoint, higher_order, Ann, Id, {result, Ret}})
+      || Name /= "init" ],  %% init can return higher-order values, since they're written to the store
+                            %% rather than being returned.
+    ok.
+
+ensure_monomorphic(Type, Err) ->
+    case is_monomorphic(Type) of
+        true  -> ok;
+        false -> fcode_error(Err)
+    end.
+
+ensure_first_order(Type, Err) ->
+    case is_first_order(Type) of
+        true  -> ok;
+        false -> fcode_error(Err)
+    end.
+
+is_monomorphic({tvar, _})              -> false;
+is_monomorphic(Ts) when is_list(Ts)    -> lists:all(fun is_monomorphic/1, Ts);
+is_monomorphic(Tup) when is_tuple(Tup) -> is_monomorphic(tuple_to_list(Tup));
+is_monomorphic(_)                      -> true.
+
+is_first_order({function, _, _})       -> false;
+is_first_order(Ts) when is_list(Ts)    -> lists:all(fun is_first_order/1, Ts);
+is_first_order(Tup) when is_tuple(Tup) -> is_first_order(tuple_to_list(Tup));
+is_first_order(_)                      -> true.
+
 %% -- Pattern matching --
 
 -spec alts_to_fcode(env(), ftype(), var_name(), [aeso_syntax:alt()], aeso_syntax:expr()) -> fsplit().
@@ -1134,11 +1205,11 @@ builtin_to_fcode(_Layout, Builtin, Args) ->
 
 %% -- Init function --
 
-add_init_function(Env, Funs0) ->
+add_init_function(Env, Main, StateType, Funs0) ->
     case is_no_code(Env) of
         true  -> Funs0;
         false ->
-            Funs     = add_default_init_function(Env, Funs0),
+            Funs     = add_default_init_function(Env, Main, StateType, Funs0),
             InitName = {entrypoint, <<"init">>},
             InitFun  = #{ body := InitBody} = maps:get(InitName, Funs),
             Funs1 = Funs#{ InitName => InitFun#{ return => {tuple, []},
@@ -1146,14 +1217,16 @@ add_init_function(Env, Funs0) ->
             Funs1
     end.
 
-add_default_init_function(_Env, Funs) ->
+add_default_init_function(_Env, Main, StateType, Funs) ->
     InitName = {entrypoint, <<"init">>},
     case maps:get(InitName, Funs, none) of
-        none ->
+        %% Only add default init function if state is unit.
+        none when StateType == {tuple, []} ->
             Funs#{ InitName => #{attrs  => [],
                                  args   => [],
                                  return => {tuple, []},
                                  body   => {tuple, []}} };
+        none -> fcode_error({missing_init_function, Main});
         _    -> Funs
     end.
 
@@ -2019,9 +2092,7 @@ setnth(I, X, Xs) ->
 -dialyzer({nowarn_function, [fcode_error/1, internal_error/1]}).
 
 fcode_error(Error) ->
-    Pos = aeso_errors:pos(0, 0),
-    Msg = lists:flatten(io_lib:format("Unknown error: ~p\n", [Error])),
-    aeso_errors:throw(aeso_errors:new(code_error, Pos, Msg)).
+    aeso_errors:throw(aeso_code_errors:format(Error)).
 
 internal_error(Error) ->
     Msg = lists:flatten(io_lib:format("~p\n", [Error])),

src/aeso_code_errors.erl

@@ -0,0 +1,94 @@
+%%%-------------------------------------------------------------------
+%%% @author Ulf Norell
+%%% @copyright (C) 2019, Aeternity Anstalt
+%%% @doc
+%%%     Formatting of code generation errors.
+%%% @end
+%%%
+%%%-------------------------------------------------------------------
+-module(aeso_code_errors).
+
+-export([format/1, pos/1]).
+
+format({last_declaration_must_be_main_contract, Decl = {Kind, _, {con, _, C}, _}}) ->
+    Msg = io_lib:format("Expected a main contract as the last declaration instead of the ~p '~s'",
+                        [Kind, C]),
+    mk_err(pos(Decl), Msg);
+format({missing_init_function, Con}) ->
+    Msg = io_lib:format("Missing init function for the contract '~s'.", [pp_expr(Con)]),
+    Cxt = "The 'init' function can only be omitted if the state type is 'unit'.",
+    mk_err(pos(Con), Msg, Cxt);
+format({missing_definition, Id}) ->
+    Msg = io_lib:format("Missing definition of function '~s'.", [pp_expr(Id)]),
+    mk_err(pos(Id), Msg);
+format({parameterized_state, Decl}) ->
+    Msg = "The state type cannot be parameterized.",
+    mk_err(pos(Decl), Msg);
+format({parameterized_event, Decl}) ->
+    Msg = "The event type cannot be parameterized.",
+    mk_err(pos(Decl), Msg);
+format({invalid_entrypoint, Why, Ann, {id, _, Name}, Thing}) ->
+    What = case Why of higher_order -> "higher-order (contains function types)";
+                       polymorphic  -> "polymorphic (contains type variables)" end,
+    ThingS = case Thing of
+                 {argument, X, T} -> io_lib:format("argument\n~s\n", [pp_typed(X, T)]);
+                 {result, T}      -> io_lib:format("return type\n~s\n", [pp_type(2, T)])
+             end,
+    Bad = case Thing of
+              {argument, _, _} -> io_lib:format("has a ~s type", [What]);
+              {result, _}      -> io_lib:format("is ~s", [What])
+          end,
+    Msg = io_lib:format("The ~sof entrypoint '~s' ~s.",
+                        [ThingS, Name, Bad]),
+    case Why of
+        higher_order -> mk_err(pos(Ann), Msg)
+    end;
+format({invalid_aens_resolve_type, Ann, T}) ->
+    Msg = io_lib:format("Invalid return type of AENS.resolve:\n"
+                        "~s\n"
+                        "It must be a string or a pubkey type (address, oracle, etc).",
+                        [pp_type(2, T)]),
+    mk_err(pos(Ann), Msg);
+format({invalid_oracle_type, Why, What, Ann, Type}) ->
+    WhyS = case Why of higher_order -> "higher-order (contain function types)";
+                       polymorphic  -> "polymorphic (contain type variables)" end,
+    Msg = io_lib:format("Invalid oracle type\n~s", [pp_type(2, Type)]),
+    Cxt = io_lib:format("The ~s type must not be ~s.", [What, WhyS]),
+    mk_err(pos(Ann), Msg, Cxt);
+format({var_args_not_set, Expr}) ->
+    mk_err( pos(Expr), "Could not deduce type of variable arguments list"
+          , "When compiling " ++ pp_expr(Expr)
+          );
+format({found_void, Ann}) ->
+    mk_err(pos(Ann), "Found a void-typed value.", "`void` is a restricted, uninhabited type. Did you mean `unit`?");
+
+format(Err) ->
+    mk_err(aeso_errors:pos(0, 0), io_lib:format("Unknown error: ~p\n", [Err])).
+
+pos(Ann) ->
+    File = aeso_syntax:get_ann(file, Ann, no_file),
+    Line = aeso_syntax:get_ann(line, Ann, 0),
+    Col  = aeso_syntax:get_ann(col, Ann, 0),
+    aeso_errors:pos(File, Line, Col).
+
+pp_typed(E, T) ->
+    prettypr:format(prettypr:nest(2,
+    lists:foldr(fun prettypr:beside/2, prettypr:empty(),
+                [aeso_pretty:expr(E), prettypr:text(" : "),
+                 aeso_pretty:type(T)]))).
+
+pp_expr(E) ->
+    pp_expr(0, E).
+
+pp_expr(N, E) ->
+    prettypr:format(prettypr:nest(N, aeso_pretty:expr(E))).
+
+pp_type(N, T) ->
+    prettypr:format(prettypr:nest(N, aeso_pretty:type(T))).
+
+mk_err(Pos, Msg) ->
+    aeso_errors:new(code_error, Pos, lists:flatten(Msg)).
+
+mk_err(Pos, Msg, Cxt) ->
+    aeso_errors:new(code_error, Pos, lists:flatten(Msg), lists:flatten(Cxt)).
+

src/aeso_compiler.erl

@@ -238,8 +238,8 @@ insert_init_function(Code, Options) ->
 
 last_contract_indent(Decls) ->
     case lists:last(Decls) of
-        {_, _, _, _, [Decl | _]} -> aeso_syntax:get_ann(col, Decl, 1) - 1;
-        _                        -> 0
+        {_, _, _, [Decl | _]} -> aeso_syntax:get_ann(col, Decl, 1) - 1;
+        _                     -> 0
     end.
 
 -spec to_sophia_value(string(), string(), ok | error | revert, binary()) ->
@@ -338,7 +338,7 @@ decode_calldata(ContractString, FunName, Calldata, Options0) ->
     end.
 
 -dialyzer({nowarn_function, get_decode_type/2}).
-get_decode_type(FunName, [{Contract, Ann, _, _, Defs}]) when ?IS_CONTRACT_HEAD(Contract) ->
+get_decode_type(FunName, [{Contract, Ann, _, Defs}]) when ?IS_CONTRACT_HEAD(Contract) ->
     GetType = fun({letfun, _, {id, _, Name}, Args, Ret, _})               when Name == FunName -> [{Args, Ret}];
                  ({fun_decl, _, {id, _, Name}, {fun_t, _, _, Args, Ret}}) when Name == FunName -> [{Args, Ret}];
                  (_) -> [] end,
@@ -349,7 +349,7 @@ get_decode_type(FunName, [{Contract, Ann, _, _, Defs}]) when ?IS_CONTRACT_HEAD(C
                 "init" -> {ok, [], {tuple_t, [], []}};
                  _ ->
                     Msg = io_lib:format("Function '~s' is missing in contract", [FunName]),
-                    Pos = aeso_errors:pos(Ann),
+                    Pos = aeso_code_errors:pos(Ann),
                     aeso_errors:throw(aeso_errors:new(data_error, Pos, Msg))
             end
     end;

src/aeso_errors.erl

@@ -34,7 +34,6 @@
         , new/2
         , new/3
         , new/4
-        , pos/1
         , pos/2
         , pos/3
         , pp/1
@@ -54,12 +53,6 @@ new(Type, Pos, Msg) ->
 new(Type, Pos, Msg, Ctxt) ->
     #err{ type = Type, pos = Pos, message = Msg, context = Ctxt }.
 
-pos(Ann) ->
-    File = aeso_syntax:get_ann(file, Ann, no_file),
-    Line = aeso_syntax:get_ann(line, Ann, 0),
-    Col  = aeso_syntax:get_ann(col, Ann, 0),
-    pos(File, Line, Col).
-
 pos(Line, Col) ->
     #pos{ line = Line, col = Col }.
 

src/aeso_fcode_to_fate.erl

@@ -64,9 +64,7 @@ debug(Tag, Options, Fun) ->
 
 -dialyzer({nowarn_function, [code_error/1]}).
 code_error(Err) ->
-    Pos = aeso_errors:pos(0, 0),
-    Msg = lists:flatten(io_lib:format("Unknown error: ~p\n", [Err])),
-    aeso_errors:throw(aeso_errors:new(code_error, Pos, Msg)).
+    aeso_errors:throw(aeso_code_errors:format(Err)).
 
 %% -- Main -------------------------------------------------------------------
 
@@ -509,8 +507,6 @@ builtin_to_scode(Env, bytes_split, [_, _] = Args) ->
     call_to_scode(Env, aeb_fate_ops:bytes_split(?a, ?a, ?a), Args);
 builtin_to_scode(Env, abort, [_] = Args) ->
     call_to_scode(Env, aeb_fate_ops:abort(?a), Args);
-builtin_to_scode(Env, exit, [_] = Args) ->
-    call_to_scode(Env, aeb_fate_ops:exit(?a), Args);
 builtin_to_scode(Env, chain_spend, [_, _] = Args) ->
     call_to_scode(Env, [aeb_fate_ops:spend(?a, ?a),
                         tuple(0)], Args);
@@ -1490,7 +1486,6 @@ r_write_to_dead_var({i, Ann, I}, Code) ->
 r_write_to_dead_var(_, _) -> false.
 
 op_view({'ABORT', R}) -> {'ABORT', none, [R]};
-op_view({'EXIT', R}) -> {'EXIT', none, [R]};
 op_view(T) when is_tuple(T) ->
     [Op, R | As] = tuple_to_list(T),
     CheckReads = fun(Rs, X) -> case [] == Rs -- [dst, src] of true -> X; false -> false end end,

src/aeso_parser.erl

@@ -96,29 +96,17 @@ decl() ->
     choice(
       %% Contract declaration
     [ ?RULE(token(main), keyword(contract),
-            con(), tok('='), maybe_block(decl()), {contract_main, _2, _3, [], _5})
-    , ?RULE(token(main), keyword(contract),
-            con(), tok(':'), comma_sep(con()), tok('='), maybe_block(decl()), {contract_main, _2, _3, _5, _7})
+            con(), tok('='), maybe_block(decl()), {contract_main, _2, _3, _5})
     , ?RULE(keyword(contract),
-            con(), tok('='), maybe_block(decl()), {contract_child, _1, _2, [], _4})
-    , ?RULE(keyword(contract),
-            con(), tok(':'), comma_sep(con()), tok('='), maybe_block(decl()), {contract_child, _1, _2, _4, _6})
+            con(), tok('='), maybe_block(decl()), {contract_child, _1, _2, _4})
     , ?RULE(keyword(contract), token(interface),
-            con(), tok('='), maybe_block(decl()), {contract_interface, _1, _3, [], _5})
-    , ?RULE(keyword(contract), token(interface),
-            con(), tok(':'), comma_sep(con()), tok('='), maybe_block(decl()), {contract_interface, _1, _3, _5, _7})
+            con(), tok('='), maybe_block(decl()), {contract_interface, _1, _3, _5})
     , ?RULE(token(payable), token(main), keyword(contract),
-            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_main, _3, _4, [], _6}))
-    , ?RULE(token(payable), token(main), keyword(contract),
-            con(), tok(':'), comma_sep(con()), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_main, _3, _4, _6, _8}))
+            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_main, _3, _4, _6}))
     , ?RULE(token(payable), keyword(contract),
-            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_child, _2, _3, [], _5}))
-    , ?RULE(token(payable), keyword(contract),
-            con(), tok(':'), comma_sep(con()), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_child, _2, _3, _5, _7}))
+            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_child, _2, _3, _5}))
     , ?RULE(token(payable), keyword(contract), token(interface),
-            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_interface, _2, _4, [], _6}))
-    , ?RULE(token(payable), keyword(contract), token(interface),
-            con(), tok(':'), comma_sep(con()), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_interface, _2, _4, _6, _8}))
+            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_interface, _2, _4, _6}))
 
 
     , ?RULE(keyword(namespace), con(), tok('='), maybe_block(decl()), {namespace, _1, _2, _4})
@@ -146,9 +134,19 @@ fun_block(Mods, Kind, [Decl]) ->
 fun_block(Mods, Kind, Decls) ->
     {block, get_ann(Kind), [ add_modifiers(Mods, Kind, Decl) || Decl <- Decls ]}.
 
+typevar_constraint() ->
+    ?RULE(tvar(), keyword(is), id(), {constraint, get_ann(_1), _1, _3}).
+
+typevars_constraints() ->
+    ?RULE(comma_sep1(typevar_constraint()), tok(';'), _1).
+
+fundecl() ->
+    choice([?RULE(id(), tok(':'), typevars_constraints(), type(),
+                  {fun_decl, get_ann(_1), _1, {constrained_t, get_ann(_1), _3, _4}}),
+            ?RULE(id(), tok(':'), type(), {fun_decl, get_ann(_1), _1, _3})]).
+
 fundef_or_decl() ->
-    choice([?RULE(id(), tok(':'), type(), {fun_decl, get_ann(_1), _1, _3}),
-            fundef()]).
+    choice([fundecl(), fundef()]).
 
 using() ->
     Alias = {keyword(as), con()},
@@ -539,6 +537,7 @@ parens(P)   -> between(tok('('), P, tok(')')).
 braces(P)   -> between(tok('{'), P, tok('}')).
 brackets(P) -> between(tok('['), P, tok(']')).
 comma_sep(P) -> sep(P, tok(',')).
+comma_sep1(P) -> sep1(P, tok(',')).
 
 paren_list(P)   -> parens(comma_sep(P)).
 brace_list(P)   -> braces(comma_sep(P)).

src/aeso_pretty.erl

@@ -151,16 +151,12 @@ decl(D, Options) ->
     with_options(Options, fun() -> decl(D) end).
 
 -spec decl(aeso_syntax:decl()) -> doc().
-decl({Con, Attrs, C, Is, Ds}) when ?IS_CONTRACT_HEAD(Con) ->
+decl({Con, Attrs, C, Ds}) when ?IS_CONTRACT_HEAD(Con) ->
     Mod = fun({Mod, true}) when Mod == payable ->
                   text(atom_to_list(Mod));
              (_) -> empty() end,
-    ImplsList = case Is of
-                    [] -> [empty()];
-                    _  -> [text(":"), par(punctuate(text(","), lists:map(fun name/1, Is)), 0)]
-                end,
     block(follow( hsep(lists:map(Mod, Attrs) ++ [contract_head(Con)])
-                , hsep([name(C)] ++ ImplsList ++ [text("=")])), decls(Ds));
+                , hsep(name(C), text("="))), decls(Ds));
 decl({namespace, _, C, Ds}) ->
     block(follow(text("namespace"), hsep(name(C), text("="))), decls(Ds));
 decl({pragma, _, Pragma}) -> pragma(Pragma);
@@ -288,7 +284,9 @@ type(T = {id, _, _})   -> name(T);
 type(T = {qid, _, _})  -> name(T);
 type(T = {con, _, _})  -> name(T);
 type(T = {qcon, _, _}) -> name(T);
-type(T = {tvar, _, _}) -> name(T).
+type(T = {tvar, _, _}) -> name(T);
+type({constrained_t, _, Cs, T}) ->
+    beside([name(T), text(" is "), tuple(lists:map(fun expr/1, Cs))]).
 
 -spec args_type([aeso_syntax:type()]) -> doc().
 args_type(Args) ->

src/aeso_scan.erl

@@ -45,7 +45,7 @@ lexer() ->
 
     Keywords = ["contract", "include", "let", "switch", "type", "record", "datatype", "if", "elif", "else", "function",
                 "stateful", "payable", "true", "false", "mod", "public", "entrypoint", "private", "indexed", "namespace",
-                "interface", "main", "using", "as", "for", "hiding"
+                "interface", "main", "using", "as", "for", "hiding", "is"
                ],
     KW = string:join(Keywords, "|"),
 

src/aeso_syntax.erl

@@ -26,7 +26,7 @@
 -type ann_format() :: '?:' | hex | infix | prefix | elif.
 
 -type ann() :: [ {line, ann_line()} | {col, ann_col()} | {format, ann_format()} | {origin, ann_origin()}
-               | stateful | private | payable | main | interface | entrypoint].
+               | stateful | private | payable | main | interface].
 
 -type name() :: string().
 -type id()   :: {id,   ann(), name()}.
@@ -38,11 +38,10 @@
 -type namespace_alias() :: none | con().
 -type namespace_parts() :: none | {for, [id()]} | {hiding, [id()]}.
 
--type decl() :: {contract_main, ann(), con(), [con()], [decl()]}
-              | {contract_child, ann(), con(), [con()], [decl()]}
-              | {contract_interface, ann(), con(), [con()], [decl()]}
+-type decl() :: {contract_main, ann(), con(), [decl()]}
+              | {contract_child, ann(), con(), [decl()]}
+              | {contract_interface, ann(), con(), [decl()]}
               | {namespace, ann(), con(), [decl()]}
-              | {include, ann(), {string, ann(), string()}}
               | {pragma, ann(), pragma()}
               | {type_decl, ann(), id(), [tvar()]} % Only for error msgs
               | {type_def, ann(), id(), [tvar()], typedef()}
@@ -80,11 +79,14 @@
 
 -type constructor_t() :: {constr_t, ann(), con(), [type()]}.
 
+-type tvar_constraint() :: {constraint, ann(), tvar(), id()}.
+
 -type type() :: {fun_t, ann(), [named_arg_t()], [type()], type()}
               | {app_t, ann(), type(), [type()]}
               | {tuple_t, ann(), [type()]}
               | {args_t, ann(), [type()]}   %% old tuple syntax, old for error messages
               | {bytes_t, ann(), integer() | any}
+              | {constrained_t, ann(), [tvar_constraint()], type()}
               | id()  | qid()
               | con() | qcon()  %% contracts
               | tvar().

src/aeso_syntax_utils.erl

@@ -61,6 +61,7 @@ fold(Alg = #alg{zero = Zero, plus = Plus, scoped = Scoped}, Fun, K, X) ->
             {fun_t, _, Named, Args, Ret} -> Type([Named, Args, Ret]);
             {app_t, _, T, Ts}            -> Type([T | Ts]);
             {tuple_t, _, Ts}             -> Type(Ts);
+            {constrained_t, _, _, T}     -> Type(T);
             %% named_arg_t()
             {named_arg_t, _, _, T, E} -> Plus(Type(T), Expr(E));
             %% expr()

src/aesophia.app.src

@@ -1,6 +1,6 @@
 {application, aesophia,
  [{description, "Compiler for Aeternity Sophia language"},
-  {vsn, "7.0.0"},
+  {vsn, "6.1.0"},
   {registered, []},
   {applications,
    [kernel,

test/aeso_aci_tests.erl

@@ -127,7 +127,7 @@ check_stub(Stub, Options) ->
         Ast ->
             try
                 %% io:format("AST: ~120p\n", [Ast]),
-                aeso_ast_infer_types:infer(Ast, [no_code])
+                aeso_ast_infer_types:infer(Ast, [])
             catch throw:{type_errors, TE} ->
                 io:format("Type error:\n~s\n", [TE]),
                 error(TE);

test/aeso_calldata_tests.erl

@@ -29,7 +29,7 @@ calldata_aci_test_() ->
      [ {"Testing " ++ ContractName ++ " contract calling " ++ Fun,
         fun() ->
            ContractString       = aeso_test_utils:read_contract(ContractName),
-           {ok, ContractACIBin} = aeso_aci:contract_interface(string, ContractString, [no_code]),
+           {ok, ContractACIBin} = aeso_aci:contract_interface(string, ContractString),
            ContractACI = binary_to_list(ContractACIBin),
            io:format("ACI:\n~s\n", [ContractACIBin]),
            FateExprs = ast_exprs(ContractACI, Fun, Args),
@@ -39,7 +39,7 @@ calldata_aci_test_() ->
         end} || {ContractName, Fun, Args} <- compilable_contracts()].
 
 parse_args(Fun, Args) ->
-    [{contract_main, _, _, _, [{letfun, _, _, _, _, [{guarded, _, [], {app, _, _, AST}}]}]}] =
+    [{contract_main, _, _, [{letfun, _, _, _, _, [{guarded, _, [], {app, _, _, AST}}]}]}] =
         aeso_parser:string("main contract Temp = function foo() = " ++ Fun ++ "(" ++ string:join(Args, ", ") ++ ")"),
     strip_ann(AST).
 

test/aeso_compiler_tests.erl

@@ -45,6 +45,12 @@ simple_compile_test_() ->
            check_errors(ExpectedErrors, Errors)
        end} ||
            {ContractName, ExpectedErrors} <- failing_contracts() ] ++
+    [ {"Testing code generation error messages of " ++ ContractName,
+       fun() ->
+               Errors = compile(ContractName),
+               check_errors([ExpectedError], Errors)
+       end} ||
+           {ContractName, ExpectedError} <- failing_code_gen_contracts()] ++
     [ {"Testing include with explicit files",
        fun() ->
            FileSystem = maps:from_list(
@@ -196,24 +202,6 @@ compilable_contracts() ->
      "assign_patterns",
      "patterns_guards",
      "pipe_operator",
-     "polymorphism_contract_implements_interface",
-     "polymorphism_contract_multi_interface",
-     "polymorphism_contract_interface_extends_interface",
-     "polymorphism_contract_interface_extensions",
-     "polymorphism_contract_interface_same_decl_multi_interface",
-     "polymorphism_contract_interface_same_name_same_type",
-     "missing_init_fun_state_unit",
-     "complex_compare_leq",
-     "complex_compare",
-     "higher_order_compare",
-     "higher_order_map_keys",
-     "higher_order_state",
-     "polymorphic_compare",
-     "polymorphic_entrypoint",
-     "polymorphic_entrypoint_return",
-     "polymorphic_map_keys",
-     "unapplied_contract_call",
-     "unapplied_named_arg_builtin",
      "test" % Custom general-purpose test file. Keep it last on the list.
     ].
 
@@ -277,7 +265,9 @@ warnings() ->
         "The function `called_unused_function2` is defined but never used.">>,
       <<?PosW(48, 5)
         "Unused return value.">>,
-      <<?PosW(60, 5)
+      <<?PosW(53, 44)
+        "The constraint on the type variable `'a` is a duplication of the constraint at line 53, column 34">>,
+      <<?PosW(65, 5)
         "The function `dec` is defined but never used.">>
      ]).
 
@@ -295,26 +285,34 @@ failing_contracts() ->
 
     %% Type errors
     , ?TYPE_ERROR(name_clash,
-       [<<?Pos(4, 3)
-          "Duplicate definitions of `double_def` at\n"
-          "  - line 3, column 3\n"
-          "  - line 4, column 3">>,
-        <<?Pos(7, 3)
+       [<<?Pos(14, 3)
           "Duplicate definitions of `abort` at\n"
           "  - (builtin location)\n"
-          "  - line 7, column 3">>,
-        <<?Pos(8, 3)
+          "  - line 14, column 3">>,
+        <<?Pos(15, 3)
           "Duplicate definitions of `require` at\n"
           "  - (builtin location)\n"
+          "  - line 15, column 3">>,
+        <<?Pos(11, 3)
+          "Duplicate definitions of `double_def` at\n"
+          "  - line 10, column 3\n"
+          "  - line 11, column 3">>,
+        <<?Pos(5, 3)
+          "Duplicate definitions of `double_proto` at\n"
+          "  - line 4, column 3\n"
+          "  - line 5, column 3">>,
+        <<?Pos(8, 3)
+          "Duplicate definitions of `proto_and_def` at\n"
+          "  - line 7, column 3\n"
           "  - line 8, column 3">>,
-        <<?Pos(9, 3)
+        <<?Pos(16, 3)
           "Duplicate definitions of `put` at\n"
           "  - (builtin location)\n"
-          "  - line 9, column 3">>,
-        <<?Pos(10, 3)
+          "  - line 16, column 3">>,
+        <<?Pos(17, 3)
           "Duplicate definitions of `state` at\n"
           "  - (builtin location)\n"
-          "  - line 10, column 3">>])
+          "  - line 17, column 3">>])
     , ?TYPE_ERROR(type_errors,
        [<<?Pos(17, 23)
           "Unbound variable `zz`">>,
@@ -568,7 +566,7 @@ failing_contracts() ->
       ])
     , ?TYPE_ERROR(list_comp_bad_shadow,
       [<<?Pos(2, 53)
-         "Cannot unify `string` and `int`\n"
+         "Cannot unify `int` and `string`\n"
          "when checking the type of the pattern `x : int` against the expected type `string`">>
       ])
     , ?TYPE_ERROR(map_as_map_key,
@@ -809,6 +807,88 @@ failing_contracts() ->
                      "to arguments\n"
                      "  `1 : int`">>
                   ])
+    , ?TYPE_ERROR(comparable_typevar_constraints,
+                  [<<?Pos(21,30)
+                     "Values of type `'a` are not comparable by equality">>,
+                   <<?Pos(25,38)
+                     "The type variable `'b` is constrained but never used">>,
+                   <<?Pos(29,41)
+                     "Unknown constraint `foo` used on the type variable `'a`">>,
+                   <<?Pos(63,58)
+                     "Values of type `Chain.ttl` are not comparable by inequality">>,
+                   <<?Pos(66,45)
+                     "Values of type `A` are not comparable by inequality">>,
+                   <<?Pos(73,47)
+                     "Values of type `(int, char) => bool` are not comparable by inequality">>,
+                   <<?Pos(74,47)
+                     "Values of type `(int, char) => bool` are not comparable by equality">>,
+                   <<?Pos(89,59)
+                     "Values of type `list(A)` are not comparable by inequality">>,
+                   <<?Pos(92,65)
+                     "Values of type `option(A)` are not comparable by inequality">>,
+                   <<?Pos(95,64)
+                     "Values of type `(A * int)` are not comparable by inequality">>,
+                   <<?Pos(96,64)
+                     "Values of type `(A * int)` are not comparable by equality">>,
+                   <<?Pos(100,68)
+                     "Values of type `list((int, char) => bool)` are not comparable by inequality">>,
+                   <<?Pos(101,68)
+                     "Values of type `list((int, char) => bool)` are not comparable by equality">>,
+                   <<?Pos(103,74)
+                     "Values of type `option((int, char) => bool)` are not comparable by inequality">>,
+                   <<?Pos(104,74)
+                     "Values of type `option((int, char) => bool)` are not comparable by equality">>,
+                   <<?Pos(106,73)
+                     "Values of type `((int, char) => bool * int)` are not comparable by inequality">>,
+                   <<?Pos(107,73)
+                     "Values of type `((int, char) => bool * int)` are not comparable by equality">>,
+                   <<?Pos(111,71)
+                     "Values of type `map(int, int)` are not comparable by inequality">>,
+                   <<?Pos(114,80)
+                     "Values of type `oracle(int, int)` are not comparable by inequality">>,
+                   <<?Pos(117,98)
+                     "Values of type `oracle_query(int, int)` are not comparable by inequality">>,
+                   <<?Pos(120,90)
+                     "Values of type `custom_datatype(int)` are not comparable by inequality">>,
+                   <<?Pos(123,84)
+                     "Values of type `custom_record(int)` are not comparable by inequality">>,
+                   <<?Pos(128,62)
+                     "Values of type `map(A, A)` are not comparable by inequality">>,
+                   <<?Pos(131,71)
+                     "Values of type `oracle(A, A)` are not comparable by inequality">>,
+                   <<?Pos(134,89)
+                     "Values of type `oracle_query(A, A)` are not comparable by inequality">>,
+                   <<?Pos(137,85)
+                     "Values of type `custom_datatype(A)` are not comparable by inequality">>,
+                   <<?Pos(140,79)
+                     "Values of type `custom_record(A)` are not comparable by inequality">>,
+                   <<?Pos(145,75)
+                     "Values of type `map((int, char) => bool, (int, char) => bool)` are not comparable by inequality">>,
+                   <<?Pos(146,75)
+                     "Values of type `map((int, char) => bool, (int, char) => bool)` are not comparable by equality">>,
+                   <<?Pos(148,84)
+                     "Values of type `oracle((int, char) => bool, (int, char) => bool)` are not comparable by inequality">>,
+                   <<?Pos(149,84)
+                     "Values of type `oracle((int, char) => bool, (int, char) => bool)` are not comparable by equality">>,
+                   <<?Pos(151,102)
+                     "Values of type `oracle_query((int, char) => bool, (int, char) => bool)` are not comparable by inequality">>,
+                   <<?Pos(152,102)
+                     "Values of type `oracle_query((int, char) => bool, (int, char) => bool)` are not comparable by equality">>,
+                   <<?Pos(154,94)
+                     "Values of type `custom_datatype((int, char) => bool)` are not comparable by inequality">>,
+                   <<?Pos(155,94)
+                     "Values of type `custom_datatype((int, char) => bool)` are not comparable by equality">>,
+                   <<?Pos(157,88)
+                     "Values of type `custom_record((int, char) => bool)` are not comparable by inequality">>,
+                   <<?Pos(158,88)
+                     "Values of type `custom_record((int, char) => bool)` are not comparable by equality">>,
+                   <<?Pos(162,35)
+                     "Values of type `map(int, int)` are not comparable by inequality">>,
+                   <<?Pos(163,35)
+                     "Values of type `('a) => 'a` are not comparable by inequality">>,
+                   <<?Pos(167,34)
+                     "Values of type `('b) => 'b` are not comparable by equality">>
+                  ])
     , ?TYPE_ERROR(warnings,
                   [<<?Pos(0, 0)
                       "The file `Triple.aes` is included but not used.">>,
@@ -838,277 +918,62 @@ failing_contracts() ->
                      "The function `called_unused_function2` is defined but never used.">>,
                    <<?Pos(48, 5)
                      "Unused return value.">>,
-                   <<?Pos(60, 5)
+                   <<?Pos(53, 44)
+                     "The constraint on the type variable `'a` is a duplication of the constraint at line 53, column 34">>,
+                   <<?Pos(65, 5)
                      "The function `dec` is defined but never used.">>
                   ])
-    , ?TYPE_ERROR(polymorphism_contract_interface_recursive,
-                  [<<?Pos(1,24)
-                     "Trying to implement or extend an undefined interface `Z`">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_contract_interface_same_name_different_type,
-                  [<<?Pos(4,20)
-                     "Unimplemented function `f` from the interface `I1` in the contract `I2`">>])
-    , ?TYPE_ERROR(polymorphism_contract_missing_implementation,
-                  [<<?Pos(4,20)
-                     "Unimplemented function `f` from the interface `I1` in the contract `I2`">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_contract_same_decl_multi_interface,
-                  [<<?Pos(7,10)
-                     "Unimplemented function `f` from the interface `J` in the contract `C`">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_contract_undefined_interface,
-                  [<<?Pos(1,14)
-                     "Trying to implement or extend an undefined interface `I`">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_contract_same_name_different_type_multi_interface,
-                  [<<?Pos(9,5)
-                     "Duplicate definitions of `f` at\n"
-                     "  - line 8, column 5\n"
-                     "  - line 9, column 5">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_contract_interface_undefined_interface,
-                  [<<?Pos(1,24)
-                     "Trying to implement or extend an undefined interface `H`">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_variance_switching,
-                  [<<?Pos(36,49)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the application of\n"
-                     "  `g2 : (Cat) => Cat`\n"
-                     "to arguments\n"
-                     "  `x : Animal`">>,
-                   <<?Pos(39,43)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the expression `g3(x) : Animal` against the expected type `Cat`">>,
-                   <<?Pos(48,55)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the application of\n"
-                     "  `g5 : ((Animal) => Animal) => Cat`\n"
-                     "to arguments\n"
-                     "  `x : (Cat) => Cat`">>,
-                   <<?Pos(52,44)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the expression `f6() : option(Animal)` against the expected type `option(Cat)`">>,
-                   <<?Pos(73,43)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the expression `some_animal : Animal` against the expected type `Cat`">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_variance_switching_custom_types,
-                  [<<?Pos(56,39)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_CONTRA(f_c_to_u) : dt_contra(Cat)` against the expected type `dt_contra(Animal)`">>,
-                   <<?Pos(62,35)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the expression `DT_CO(f_u_to_a) : dt_co(Animal)` against the expected type `dt_co(Cat)`">>,
-                   <<?Pos(67,36)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the application of\n  `DT_INV : ((Cat) => Cat) => dt_inv(Cat)`\nto arguments\n  `f_c_to_a : (Cat) => Animal`">>,
-                   <<?Pos(68,36)
-                     "Cannot unify `Cat` and `Animal` in a invariant context\n"
-                     "when checking the type of the expression `DT_INV(f_c_to_c) : dt_inv(Cat)` against the expected type `dt_inv(Animal)`">>,
-                   <<?Pos(69,36)
-                     "Cannot unify `Animal` and `Cat` in a invariant context\n"
-                     "when checking the type of the expression `DT_INV(f_a_to_a) : dt_inv(Animal)` against the expected type `dt_inv(Cat)`">>,
-                   <<?Pos(70,36)
-                     "Cannot unify `Animal` and `Cat` in a invariant context\n"
-                     "when checking the type of the expression `DT_INV(f_a_to_c) : dt_inv(Animal)` against the expected type `dt_inv(Cat)`">>,
-                   <<?Pos(71,36)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the application of\n  `DT_INV : ((Cat) => Cat) => dt_inv(Cat)`\nto arguments\n  `f_c_to_a : (Cat) => Animal`">>,
-                   <<?Pos(80,40)
-                     "Cannot unify `Cat` and `Animal` in a invariant context\n"
-                     "when checking the type of the expression `DT_INV_SEP_A(f_c_to_u) : dt_inv_sep(Cat)` against the expected type `dt_inv_sep(Animal)`">>,
-                   <<?Pos(82,40)
-                     "Cannot unify `Cat` and `Animal` in a invariant context\n"
-                     "when checking the type of the expression `DT_INV_SEP_B(f_u_to_c) : dt_inv_sep(Cat)` against the expected type `dt_inv_sep(Animal)`">>,
-                   <<?Pos(83,40)
-                     "Cannot unify `Animal` and `Cat` in a invariant context\n"
-                     "when checking the type of the expression `DT_INV_SEP_A(f_a_to_u) : dt_inv_sep(Animal)` against the expected type `dt_inv_sep(Cat)`">>,
-                   <<?Pos(85,40)
-                     "Cannot unify `Animal` and `Cat` in a invariant context\n"
-                     "when checking the type of the expression `DT_INV_SEP_B(f_u_to_a) : dt_inv_sep(Animal)` against the expected type `dt_inv_sep(Cat)`">>,
-                   <<?Pos(90,42)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the expression `DT_CO_NEST_A(f_dt_contra_a_to_u) : dt_co_nest_a(Animal)` against the expected type `dt_co_nest_a(Cat)`">>,
-                   <<?Pos(94,46)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_CONTRA_NEST_A(f_dt_co_c_to_u) : dt_contra_nest_a(Cat)` against the expected type `dt_contra_nest_a(Animal)`">>,
-                   <<?Pos(99,46)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_CONTRA_NEST_B(f_u_to_dt_contra_c) : dt_contra_nest_b(Cat)` against the expected type `dt_contra_nest_b(Animal)`">>,
-                   <<?Pos(105,42)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the expression `DT_CO_NEST_B(f_u_to_dt_co_a) : dt_co_nest_b(Animal)` against the expected type `dt_co_nest_b(Cat)`">>,
-                   <<?Pos(110,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `vj3 : dt_co_twice(Cat)` against the expected type `dt_co_twice(Animal)`">>,
-                   <<?Pos(114,59)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_A_CONTRA_B_CONTRA(f_a_to_c_to_u) : dt_a_contra_b_contra(Animal, Cat)` against the expected type `dt_a_contra_b_contra(Animal, Animal)`">>,
-                   <<?Pos(115,59)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_A_CONTRA_B_CONTRA(f_c_to_a_to_u) : dt_a_contra_b_contra(Cat, Animal)` against the expected type `dt_a_contra_b_contra(Animal, Animal)`">>,
-                   <<?Pos(116,59)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_A_CONTRA_B_CONTRA(f_c_to_c_to_u) : dt_a_contra_b_contra(Cat, Cat)` against the expected type `dt_a_contra_b_contra(Animal, Animal)`">>,
-                   <<?Pos(119,59)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_A_CONTRA_B_CONTRA(f_c_to_a_to_u) : dt_a_contra_b_contra(Cat, Animal)` against the expected type `dt_a_contra_b_contra(Animal, Cat)`">>,
-                   <<?Pos(120,59)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_A_CONTRA_B_CONTRA(f_c_to_c_to_u) : dt_a_contra_b_contra(Cat, Cat)` against the expected type `dt_a_contra_b_contra(Animal, Cat)`">>,
-                   <<?Pos(122,59)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_A_CONTRA_B_CONTRA(f_a_to_c_to_u) : dt_a_contra_b_contra(Animal, Cat)` against the expected type `dt_a_contra_b_contra(Cat, Animal)`">>,
-                   <<?Pos(124,59)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the expression `DT_A_CONTRA_B_CONTRA(f_c_to_c_to_u) : dt_a_contra_b_contra(Cat, Cat)` against the expected type `dt_a_contra_b_contra(Cat, Animal)`">>,
-                   <<?Pos(131,13)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the pattern `vl2 : dt_contra_twice(Animal)` against the expected type `dt_contra_twice(Cat)`">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_variance_switching_records,
-                  [<<?Pos(27,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `r03 : rec_co(Cat)` against the expected type `Main.rec_co(Animal)`">>,
-                   <<?Pos(33,13)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the pattern `r06 : rec_contra(Animal)` against the expected type `Main.rec_contra(Cat)`">>,
-                   <<?Pos(40,13)
-                     "Cannot unify `Cat` and `Animal` in a invariant context\n"
-                     "when checking the type of the pattern `r10 : rec_inv(Animal)` against the expected type `Main.rec_inv(Cat)`">>,
-                   <<?Pos(41,13)
-                     "Cannot unify `Animal` and `Cat` in a invariant context\n"
-                     "when checking the type of the pattern `r11 : rec_inv(Cat)` against the expected type `Main.rec_inv(Animal)`">>
-                  ])
-    , ?TYPE_ERROR(polymorphism_variance_switching_oracles,
-                  [<<?Pos(15,13)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the pattern `o03 : oracle(Animal, Animal)` against the expected type `oracle(Cat, Animal)`">>,
-                   <<?Pos(16,13)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the pattern `o04 : oracle(Animal, Animal)` against the expected type `oracle(Cat, Cat)`">>,
-                   <<?Pos(17,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `o05 : oracle(Animal, Cat)` against the expected type `oracle(Animal, Animal)`">>,
-                   <<?Pos(19,13)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the pattern `o07 : oracle(Animal, Cat)` against the expected type `oracle(Cat, Animal)`">>,
-                   <<?Pos(20,13)
-                     "Cannot unify `Cat` and `Animal` in a contravariant context\n"
-                     "when checking the type of the pattern `o08 : oracle(Animal, Cat)` against the expected type `oracle(Cat, Cat)`">>,
-                   <<?Pos(25,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `o13 : oracle(Cat, Cat)` against the expected type `oracle(Animal, Animal)`">>,
-                   <<?Pos(27,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `o15 : oracle(Cat, Cat)` against the expected type `oracle(Cat, Animal)`">>,
-                   <<?Pos(34,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `q05 : oracle_query(Animal, Cat)` against the expected type `oracle_query(Animal, Animal)`">>,
-                   <<?Pos(36,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `q07 : oracle_query(Animal, Cat)` against the expected type `oracle_query(Cat, Animal)`">>,
-                   <<?Pos(38,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `q09 : oracle_query(Cat, Animal)` against the expected type `oracle_query(Animal, Animal)`">>,
-                   <<?Pos(39,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `q10 : oracle_query(Cat, Animal)` against the expected type `oracle_query(Animal, Cat)`">>,
-                   <<?Pos(42,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `q13 : oracle_query(Cat, Cat)` against the expected type `oracle_query(Animal, Animal)`">>,
-                   <<?Pos(43,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `q14 : oracle_query(Cat, Cat)` against the expected type `oracle_query(Animal, Cat)`">>,
-                   <<?Pos(44,13)
-                     "Cannot unify `Animal` and `Cat` in a covariant context\n"
-                     "when checking the type of the pattern `q15 : oracle_query(Cat, Cat)` against the expected type `oracle_query(Cat, Animal)`">>
-                  ])
-    , ?TYPE_ERROR(missing_definition,
-                  [<<?Pos(2,14)
-                     "Missing definition of function `foo`">>
-                  ])
-    , ?TYPE_ERROR(child_with_decls,
-                  [<<?Pos(2,14)
-                     "Missing definition of function `f`">>
-                  ])
-    , ?TYPE_ERROR(parameterised_state,
-                  [<<?Pos(3,8)
-                     "The state type cannot be parameterized">>
-                  ])
-    , ?TYPE_ERROR(parameterised_event,
-                  [<<?Pos(3,12)
-                     "The event type cannot be parameterized">>
-                  ])
-    , ?TYPE_ERROR(missing_init_fun_alias_to_type,
-                  [<<?Pos(1,10)
-                     "Missing `init` function for the contract `AliasToType`.\n"
-                     "The `init` function can only be omitted if the state type is `unit`">>
-                  ])
-    , ?TYPE_ERROR(missing_init_fun_alias_to_alias_to_type,
-                  [<<?Pos(1,10)
-                     "Missing `init` function for the contract `AliasToAliasToType`.\n"
-                     "The `init` function can only be omitted if the state type is `unit`">>
-                  ])
-    , ?TYPE_ERROR(higher_order_entrypoint,
-                  [<<?Pos(2,20)
-                     "The argument\n"
-                     "  `f : (int) => int`\n"
-                     "of entrypoint `apply` has a higher-order (contains function types) type">>
-                  ])
-    , ?TYPE_ERROR(higher_order_entrypoint_return,
-                  [<<?Pos(2,3)
-                     "The return type\n"
-                     "  `(int) => int`\n"
-                     "of entrypoint `add` is higher-order (contains function types)">>
-                  ])
-    , ?TYPE_ERROR(polymorphic_aens_resolve,
-                  [<<?Pos(4,5)
-                     "Invalid return type of `AENS.resolve`:\n"
-                     "  `'a`\n"
-                     "It must be a `string` or a pubkey type (`address`, `oracle`, etc)">>
-                  ])
-    , ?TYPE_ERROR(bad_aens_resolve,
-                  [<<?Pos(6,5)
-                     "Invalid return type of `AENS.resolve`:\n"
-                     "  `list(int)`\n"
-                     "It must be a `string` or a pubkey type (`address`, `oracle`, etc)">>
-                  ])
-    , ?TYPE_ERROR(bad_aens_resolve_using,
-                  [<<?Pos(7,5)
-                     "Invalid return type of `AENS.resolve`:\n"
-                     "  `list(int)`\n"
-                     "It must be a `string` or a pubkey type (`address`, `oracle`, etc)">>
-                  ])
-    , ?TYPE_ERROR(polymorphic_query_type,
-                  [<<?Pos(3,5)
-                     "Invalid oracle type\n"
-                     "  `oracle('a, 'b)`\n"
-                     "The query type must not be polymorphic (contain type variables)">>,
-                   <<?Pos(3,5)
-                     "Invalid oracle type\n"
-                     "  `oracle('a, 'b)`\n"
-                     "The response type must not be polymorphic (contain type variables)">>
-                  ])
-    , ?TYPE_ERROR(polymorphic_response_type,
-                  [<<?Pos(3,5)
-                     "Invalid oracle type\n"
-                     "  `oracle(string, 'r)`\n"
-                     "The response type must not be polymorphic (contain type variables)">>
-                  ])
-    , ?TYPE_ERROR(higher_order_query_type,
-                  [<<?Pos(3,5)
-                     "Invalid oracle type\n"
-                     "  `oracle((int) => int, string)`\n"
-                     "The query type must not be higher-order (contain function types)">>
-                  ])
-    , ?TYPE_ERROR(higher_order_response_type,
-                  [<<?Pos(3,5)
-                     "Invalid oracle type\n"
-                     "  `oracle(string, (int) => int)`\n"
-                     "The response type must not be higher-order (contain function types)">>
-                  ])
+    ].
+
+-define(Path(File), "code_errors/" ??File).
+-define(Msg(File, Line, Col, Err), <<?Pos("Code generation", ?Path(File), Line, Col) Err>>).
+
+-define(FATE_ERR(File, Line, Col, Err), {?Path(File), ?Msg(File, Line, Col, Err)}).
+
+failing_code_gen_contracts() ->
+    [ ?FATE_ERR(missing_definition, 2, 14,
+            "Missing definition of function 'foo'.")
+    , ?FATE_ERR(higher_order_entrypoint, 2, 20,
+            "The argument\n"
+            "  f : (int) => int\n"
+            "of entrypoint 'apply' has a higher-order (contains function types) type.")
+    , ?FATE_ERR(higher_order_entrypoint_return, 2, 3,
+            "The return type\n"
+            "  (int) => int\n"
+            "of entrypoint 'add' is higher-order (contains function types).")
+    , ?FATE_ERR(missing_init_function, 1, 10,
+            "Missing init function for the contract 'MissingInitFunction'.\n"
+            "The 'init' function can only be omitted if the state type is 'unit'.")
+    , ?FATE_ERR(parameterised_state, 3, 8,
+            "The state type cannot be parameterized.")
+    , ?FATE_ERR(parameterised_event, 3, 12,
+            "The event type cannot be parameterized.")
+    , ?FATE_ERR(polymorphic_aens_resolve, 4, 5,
+            "Invalid return type of AENS.resolve:\n"
+            "  'a\n"
+            "It must be a string or a pubkey type (address, oracle, etc).")
+    , ?FATE_ERR(bad_aens_resolve, 6, 5,
+            "Invalid return type of AENS.resolve:\n"
+            "  list(int)\n"
+            "It must be a string or a pubkey type (address, oracle, etc).")
+    , ?FATE_ERR(polymorphic_query_type, 3, 5,
+            "Invalid oracle type\n"
+            "  oracle('a, 'b)\n"
+            "The query type must not be polymorphic (contain type variables).")
+    , ?FATE_ERR(polymorphic_response_type, 3, 5,
+            "Invalid oracle type\n"
+            "  oracle(string, 'r)\n"
+            "The response type must not be polymorphic (contain type variables).")
+    , ?FATE_ERR(higher_order_query_type, 3, 5,
+            "Invalid oracle type\n"
+            "  oracle((int) => int, string)\n"
+            "The query type must not be higher-order (contain function types).")
+    , ?FATE_ERR(higher_order_response_type, 3, 5,
+            "Invalid oracle type\n"
+            "  oracle(string, (int) => int)\n"
+            "The response type must not be higher-order (contain function types).")
+    , ?FATE_ERR(child_with_decls, 2, 14,
+            "Missing definition of function 'f'.")
     ].
 
 validation_test_() ->

test/aeso_parser_tests.erl

@@ -15,7 +15,7 @@ simple_contracts_test_() ->
             Text = "main contract Identity =\n"
                    "  function id(x) = x\n",
             ?assertMatch(
-                [{contract_main, _, {con, _, "Identity"}, _,
+                [{contract_main, _, {con, _, "Identity"},
                     [{letfun, _, {id, _, "id"}, [{id, _, "x"}], {id, _, "_"},
                         [{guarded, _, [], {id, _, "x"}}]}]}], parse_string(Text)),
             ok

test/contracts/aens.aes

@@ -1,7 +1,5 @@
-contract C = entrypoint init() = ()
-
 // AENS tests
-main contract AENSTest =
+contract AENSTest =
 
   // Name resolution
 
@@ -11,19 +9,10 @@ main contract AENSTest =
   stateful entrypoint resolve_string(name : string, key : string) : option(string) =
     AENS.resolve(name, key)
 
-  stateful entrypoint resolve_contract(name : string, key : string) : option(C) =
-    AENS.resolve(name, key)
-
-  stateful entrypoint resolve_oracle(name : string, key : string) : option(oracle(int, int)) =
-    AENS.resolve(name, key)
-
-  stateful entrypoint resolve_oracle_query(name : string, key : string) : option(oracle_query(int, int)) =
-    AENS.resolve(name, key)
-
   // Transactions
 
   stateful entrypoint preclaim(addr  : address,     // Claim on behalf of this account (can be Contract.address)
-                               chash : hash) : unit = // Commitment hash
+                             chash : hash) : unit = // Commitment hash
     AENS.preclaim(addr, chash)
 
   stateful entrypoint signedPreclaim(addr  : address, // Claim on behalf of this account (can be Contract.address)

test/contracts/all_syntax.aes

@@ -80,4 +80,3 @@ contract AllSyntax =
      let sh : shakespeare(shakespeare(int)) =
        {wolfgang = state}
      sh{wolfgang.wolfgang = sh.wolfgang} // comment
-     exit("hope you had fun reading this")

test/contracts/bad_aens_resolve_using.aes

@@ -1,9 +0,0 @@
-contract BadAENSresolve =
-  using AENS
-
-  type t('a) = option(list('a))
-
-  function fail() : t(int) =
-    resolve("foo.aet", "whatever")
-
-  entrypoint main_fun() = ()

test/contracts/code_errors/missing_init_function.aes

@@ -0,0 +1,3 @@
+contract MissingInitFunction =
+  type state = int * int
+

test/contracts/comparable_typevar_constraints.aes

@@ -0,0 +1,169 @@
+contract A = entrypoint init() = ()
+
+main contract C =
+    datatype custom_datatype('a) = CD('a)
+
+    record custom_record('a) = { f : 'a }
+
+    // pass
+    function
+        passing_ord : 'a is ord ; ('a, 'a) => bool
+        passing_ord(x, y) = x >= y
+
+    // pass
+    function
+        passing_eq : 'a is eq ; ('a, 'a) => bool
+        passing_eq(x, y) = x == y
+
+    // fail because eq is not specified for 'a
+    function
+        fail_no_eq : ('a, 'a) => bool
+        fail_no_eq(x, y) = x == y
+
+    // fail because 'b is not used
+    function
+        fail_unused_tvar : 'a is eq, 'b is eq ; ('a, 'a) => bool
+        fail_unused_tvar(x, y) = x == y
+
+    function
+        fail_unknown_constraint : 'a is foo ; ('a) => 'a
+        fail_unknown_constraint(x) = x
+
+    // Ord types
+
+    function bool_ord(x : bool, y : bool) = x >= y  // pass
+    function bool_eq (x : bool, y : bool) = x == y  // pass
+
+    function int_ord(x : int, y : int) = x >= y  // pass
+    function int_eq (x : int, y : int) = x == y  // pass
+
+    function char_ord(x : char, y : char) = x >= y  // pass
+    function char_eq (x : char, y : char) = x == y  // pass
+
+    function bits_ord(x : bits, y : bits) = x >= y  // pass
+    function bits_eq (x : bits, y : bits) = x == y  // pass
+
+    function bytes_ord(x : bytes(16), y : bytes(16)) = x >= y  // pass
+    function bytes_eq (x : bytes(16), y : bytes(16)) = x == y  // pass
+
+    function string_ord(x : string, y : string) = x >= y  // pass
+    function string_eq (x : string, y : string) = x == y  // pass
+
+    function hash_ord(x : hash, y : hash) = x >= y  // pass
+    function hash_eq (x : hash, y : hash) = x == y  // pass
+
+    function signature_ord(x : signature, y : signature) = x >= y  // pass
+    function signature_eq (x : signature, y : signature) = x == y  // pass
+
+    function address_ord(x : address, y : address) = x >= y  // pass
+    function address_eq (x : address, y : address) = x == y  // pass
+
+    // Eq types
+
+    function event_ord(x : Chain.ttl, y : Chain.ttl) = x >= y  // fail
+    function event_eq (x : Chain.ttl, y : Chain.ttl) = x == y  // pass
+
+    function contract_ord(x : A, y : A) = x >= y  // fail
+    function contract_eq (x : A, y : A) = x == y  // pass
+
+    // Noncomparable types
+
+    type lam = (int, char) => bool
+
+    function lambda_ord(x : lam, y : lam) = x >= y  // fail
+    function lambda_eq (x : lam, y : lam) = x == y  // fail
+
+    // Ord composite types of ord
+
+    function list_of_ord_ord(x : list(int), y : list(int)) = x >= y  // pass
+    function list_of_ord_eq (x : list(int), y : list(int)) = x == y  // pass
+
+    function option_of_ord_ord(x : option(int), y : option(int)) = x >= y  // pass
+    function option_of_ord_eq (x : option(int), y : option(int)) = x == y  // pass
+
+    function tuple_of_ord_ord(x : (int * bool), y : (int * bool)) = x >= y  // pass
+    function tuple_of_ord_eq (x : (int * bool), y : (int * bool)) = x == y  // pass
+
+    // Ord composite types of eq
+
+    function list_of_eq_ord(x : list(A), y : list(A)) = x >= y  // fail
+    function list_of_eq_eq (x : list(A), y : list(A)) = x == y  // pass
+
+    function option_of_eq_ord(x : option(A), y : option(A)) = x >= y  // fail
+    function option_of_eq_eq (x : option(A), y : option(A)) = x == y  // pass
+
+    function tuple_of_eq_ord(x : (A * int), y : (A * int)) = x >= y  // fail
+    function tuple_of_eq_eq (x : (A * int), y : (A * int)) = x == y  // pass
+
+    // Ord composite types of nomcomparable
+
+    function list_of_noncomp_ord(x : list(lam), y : list(lam)) = x >= y  // fail
+    function list_of_noncomp_eq (x : list(lam), y : list(lam)) = x == y  // fail
+
+    function option_of_noncomp_ord(x : option(lam), y : option(lam)) = x >= y  // fail
+    function option_of_noncomp_eq (x : option(lam), y : option(lam)) = x == y  // fail
+
+    function tuple_of_noncomp_ord(x : (lam * int), y : (lam * int)) = x >= y  // fail
+    function tuple_of_noncomp_eq (x : (lam * int), y : (lam * int)) = x == y  // fail
+
+    // Eq composite types of ord
+
+    function map_of_ord_ord(x : map(int, int), y : map(int, int)) = x >= y  // fail
+    function map_of_ord_eq (x : map(int, int), y : map(int, int)) = x == y  // pass
+
+    function oracle_of_ord_ord(x : oracle(int, int), y : oracle(int, int)) = x >= y  // fail
+    function oracle_of_ord_eq (x : oracle(int, int), y : oracle(int, int)) = x == y  // pass
+
+    function oracle_query_of_ord_ord(x : oracle_query(int, int), y : oracle_query(int, int)) = x >= y  // fail
+    function oracle_query_of_ord_eq (x : oracle_query(int, int), y : oracle_query(int, int)) = x == y  // pass
+
+    function datatype_of_ord_ord(x : custom_datatype(int), y : custom_datatype(int)) = x >= y  // fail
+    function datatype_of_ord_eq (x : custom_datatype(int), y : custom_datatype(int)) = x == y  // pass
+
+    function record_of_ord_ord(x : custom_record(int), y : custom_record(int)) = x >= y  // fail
+    function record_of_ord_eq (x : custom_record(int), y : custom_record(int)) = x == y  // pass
+
+    // Eq composite types of eq
+
+    function map_of_eq_ord(x : map(A, A), y : map(A, A)) = x >= y  // fail
+    function map_of_eq_eq (x : map(A, A), y : map(A, A)) = x == y  // pass
+
+    function oracle_of_eq_ord(x : oracle(A, A), y : oracle(A, A)) = x >= y  // fail
+    function oracle_of_eq_eq (x : oracle(A, A), y : oracle(A, A)) = x == y  // pass
+
+    function oracle_query_of_eq_ord(x : oracle_query(A, A), y : oracle_query(A, A)) = x >= y  // fail
+    function oracle_query_of_eq_eq (x : oracle_query(A, A), y : oracle_query(A, A)) = x == y  // pass
+
+    function datatype_of_eq_ord(x : custom_datatype(A), y : custom_datatype(A)) = x >= y  // fail
+    function datatype_of_eq_eq (x : custom_datatype(A), y : custom_datatype(A)) = x == y  // pass
+
+    function record_of_eq_ord(x : custom_record(A), y : custom_record(A)) = x >= y  // fail
+    function record_of_eq_eq (x : custom_record(A), y : custom_record(A)) = x == y  // pass
+
+    // Eq composite types of nomcomparable
+
+    function map_of_noncomp_ord(x : map(lam, lam), y : map(lam, lam)) = x >= y  // fail
+    function map_of_noncomp_eq (x : map(lam, lam), y : map(lam, lam)) = x == y  // fail
+
+    function oracle_of_noncomp_ord(x : oracle(lam, lam), y : oracle(lam, lam)) = x >= y  // fail
+    function oracle_of_noncomp_eq (x : oracle(lam, lam), y : oracle(lam, lam)) = x == y  // fail
+
+    function oracle_query_of_noncomp_ord(x : oracle_query(lam, lam), y : oracle_query(lam, lam)) = x >= y  // fail
+    function oracle_query_of_noncomp_eq (x : oracle_query(lam, lam), y : oracle_query(lam, lam)) = x == y  // fail
+
+    function datatype_of_noncomp_ord(x : custom_datatype(lam), y : custom_datatype(lam)) = x >= y  // fail
+    function datatype_of_noncomp_eq (x : custom_datatype(lam), y : custom_datatype(lam)) = x == y  // pass
+
+    function record_of_nomcomp_ord(x : custom_record(lam), y : custom_record(lam)) = x >= y  // fail
+    function record_of_nomcomp_eq (x : custom_record(lam), y : custom_record(lam)) = x == y  // pass
+
+    entrypoint init() =
+        let passing_ord_ord     = passing_ord([1], [2])              // pass
+        let passing_ord_eq      = passing_ord({[1] = 2}, {[2] = 3})  // fail
+        let passing_ord_noncomp = passing_ord((x) => x, (x) => x)    // fail
+
+        let passing_eq_ord     = passing_eq([1], [2])              // pass
+        let passing_eq_eq      = passing_eq({[1] = 2}, {[2] = 3})  // pass
+        let passing_eq_noncomp = passing_eq((x) => x, (x) => x)    // fail
+
+        ()

test/contracts/missing_init_fun_alias_to_alias_to_type.aes

@@ -1,3 +0,0 @@
-contract AliasToAliasToType =
-  type alias = int * int
-  type state = alias

test/contracts/missing_init_fun_alias_to_type.aes

@@ -1,2 +0,0 @@
-contract AliasToType =
-  type state = int * int

test/contracts/missing_init_fun_state_unit.aes

@@ -1,9 +0,0 @@
-contract AliasToAliasToUnit =
-  type alias = unit
-  type state = alias
-
-contract AliasToUnit =
-  type state = unit
-
-main contract ImplicitState =
-    type sometype = int

test/contracts/name_clash.aes

@@ -1,5 +1,12 @@
+
 contract NameClash =
 
+  entrypoint double_proto : () => int
+  entrypoint double_proto : () => int
+
+  entrypoint proto_and_def : int => int
+  entrypoint proto_and_def(n) = n + 1
+
   entrypoint double_def(x) = x
   entrypoint double_def(y) = 0
 
@@ -7,4 +14,4 @@ contract NameClash =
   entrypoint abort() : int = 0
   entrypoint require(b, err) = if(b) abort(err)
   entrypoint put(x) = x
-  entrypoint state(x, y) = x + y
+  entrypoint state(x, y) = x + y

test/contracts/polymorphism_contract_implements_interface.aes

@@ -1,5 +0,0 @@
-contract interface Strokable =
-  entrypoint stroke : () => string
-
-contract Cat : Strokable =
-  entrypoint stroke() = "Cat stroke"

test/contracts/polymorphism_contract_interface_extends_interface.aes

@@ -1,10 +0,0 @@
-contract interface II =
-    entrypoint f : () => unit
-
-contract interface I : II =
-    entrypoint f : () => unit
-    entrypoint g : () => unit
-
-contract C : I =
-    entrypoint f() = ()
-    entrypoint g() = ()

test/contracts/polymorphism_contract_interface_extensions.aes

@@ -1,9 +0,0 @@
-contract interface I0 =
-  entrypoint f : () => int
-
-contract interface I1 : I0 =
-  entrypoint f : () => int
-  entrypoint something_else : () => int
-
-main contract C =
-  entrypoint f(x : I1) = x.f() // Here we should know that x has f

test/contracts/polymorphism_contract_interface_recursive.aes

@@ -1,13 +0,0 @@
-contract interface X : Z =
-    entrypoint x : () => int
-
-contract interface Y : X =
-    entrypoint y : () => int
-
-contract interface Z : Y =
-    entrypoint z : () => int
-
-contract C : Z =
-    entrypoint x() = 1
-    entrypoint y() = 1
-    entrypoint z() = 1

test/contracts/polymorphism_contract_interface_same_decl_multi_interface.aes

@@ -1,8 +0,0 @@
-contract interface I =
-    entrypoint f : () => int
-
-contract interface II : I =
-    entrypoint f : () => int
-
-contract C : II =
-    entrypoint f() = 1

test/contracts/polymorphism_contract_interface_same_name_different_type.aes

@@ -1,9 +0,0 @@
-contract interface I1 =
-    entrypoint f : () => int
-
-contract interface I2 : I1 =
-    entrypoint f : () => char
-
-contract C : I2 =
-    entrypoint f() = 1
-    entrypoint f() = 'c'

test/contracts/polymorphism_contract_interface_same_name_same_type.aes

@@ -1,8 +0,0 @@
-contract interface I1 =
-    entrypoint f : () => int
-
-contract interface I2 : I1 =
-    entrypoint f : () => int
-
-contract C : I2 =
-    entrypoint f() = 1

test/contracts/polymorphism_contract_interface_undefined_interface.aes

@@ -1,5 +0,0 @@
-contract interface I : H =
-    entrypoint f : () => unit
-
-contract C =
-    entrypoint g() = ()

test/contracts/polymorphism_contract_missing_implementation.aes

@@ -1,8 +0,0 @@
-contract interface I1 =
-    entrypoint f : () => int
-
-contract interface I2 : I1 =
-    entrypoint g : () => int
-
-contract C : I2 =
-    entrypoint g() = 1

test/contracts/polymorphism_contract_multi_interface.aes

@@ -1,9 +0,0 @@
-contract interface I =
-    entrypoint f : () => int
-
-contract interface J =
-    entrypoint g : () => char
-
-contract C : I, J =
-    entrypoint f() = 1
-    entrypoint g() = 'c'

test/contracts/polymorphism_contract_same_decl_multi_interface.aes

@@ -1,8 +0,0 @@
-contract interface I =
-    entrypoint f : () => int
-
-contract interface J =
-    entrypoint f : () => int
-
-contract C : I, J =
-    entrypoint f() = 1

test/contracts/polymorphism_contract_same_name_different_type_multi_interface.aes

@@ -1,9 +0,0 @@
-contract interface I =
-    entrypoint f : () => int
-
-contract interface J =
-    entrypoint f : () => char
-
-contract C : I, J =
-    entrypoint f() = 1
-    entrypoint f() = 'c'

test/contracts/polymorphism_contract_undefined_interface.aes

@@ -1,2 +0,0 @@
-contract C : I =
-    entrypoint f() = ()

test/contracts/polymorphism_variance_switching.aes

@@ -1,75 +0,0 @@
-contract interface Creature =
-    entrypoint is_alive : () => bool
-
-contract interface Animal : Creature =
-    entrypoint is_alive : () => bool
-    entrypoint sound : () => string
-
-contract Cat : Animal =
-    entrypoint sound() = "meow"
-    entrypoint is_alive() = true
-
-main contract Main =
-    entrypoint init() = ()
-
-    stateful function g0(_ : Creature) : Cat = Chain.create()
-    stateful function f0(x : Cat) : Creature = g0(x)
-    stateful function h0() =
-        let a : Animal = (Chain.create() : Cat)
-        let c : Creature = (Chain.create() : Cat)
-        let c1 : Creature = a
-        ()
-
-    stateful function g1(x : Animal) : Cat = Chain.create()
-    stateful function f1(x : Cat) : Animal = g1(x)
-
-    stateful function g11(x : list(Animal)) : list(Cat) = [Chain.create()]
-    stateful function f11(x : list(Cat)) : list(Animal) = g11(x)
-
-    stateful function g12(x : Animal * Animal) : Cat * Cat = (Chain.create(), Chain.create())
-    stateful function f12(x : Cat * Cat) : Animal * Animal = g12(x)
-
-    stateful function g13() : map(Cat, Cat) = { [Chain.create()] = Chain.create() }
-    stateful function f13() : map(Animal, Animal) = g13()
-
-    stateful function g2(x : Cat) : Cat = Chain.create()
-    stateful function f2(x : Animal) : Animal = g2(x)  // fail
-
-    stateful function g3(x : Cat) : Animal = f1(x)
-    stateful function f3(x : Cat) : Cat = g3(x)  // fail
-
-    stateful function g4(x : (Cat => Animal)) : Cat = Chain.create()
-    stateful function f4(x : (Animal => Cat)) : Animal = g4(x)
-
-    stateful function g44(x : list(list(Cat) => list(Animal))) : Cat = Chain.create()
-    stateful function f44(x : list(list(Animal) => list(Cat))) : Animal = g44(x)
-
-    stateful function g5(x : (Animal => Animal)) : Cat = Chain.create()
-    stateful function f5(x : (Cat => Cat)) : Animal = g5(x)  // fail
-
-    stateful function g6() : option(Cat) = Some(Chain.create())
-    stateful function f6() : option(Animal) = g6()
-    stateful function h6() : option(Cat) = f6()  // fail
-
-    type cat_type = Cat
-    type animal_type = Animal
-    type cat_cat_map = map(cat_type, cat_type)
-    type animal_animal_map = map(animal_type, animal_type)
-
-    stateful function g71(x : animal_type) : cat_type = Chain.create()
-    stateful function f71(x : cat_type) : animal_type = g1(x)
-
-    stateful function g72() : cat_cat_map = { [Chain.create()] = Chain.create() }
-    stateful function f72() : animal_animal_map = g13()
-
-    stateful function g73() =
-        let some_cat : Cat = Chain.create()
-        let some_animal : Animal = some_cat
-
-        let some_cat_cat_map : map(Cat, Cat) = g13()
-        let some_animal_animal_map : map(Animal, Animal) = some_cat_cat_map
-
-        let x : Animal = some_animal_animal_map[some_cat]  // success
-        let y : Cat    = some_cat_cat_map[some_animal]     // fail
-
-        ()

test/contracts/polymorphism_variance_switching_custom_types.aes

@@ -1,135 +0,0 @@
-contract interface Animal =
-    entrypoint sound : () => string
-
-contract Cat : Animal =
-    entrypoint sound() = "meow"
-
-main contract Main =
-    datatype dt_contra('a) = DT_CONTRA('a => unit)
-    datatype dt_co('a) = DT_CO(unit => 'a)
-    datatype dt_inv('a) = DT_INV('a => 'a)
-    datatype dt_biv('a) = DT_BIV(unit => unit)
-    datatype dt_inv_sep('a) = DT_INV_SEP_A('a => unit) | DT_INV_SEP_B(unit => 'a)
-    datatype dt_co_nest_a('a) = DT_CO_NEST_A(dt_contra('a) => unit)
-    datatype dt_contra_nest_a('a) = DT_CONTRA_NEST_A(dt_co('a) => unit)
-    datatype dt_contra_nest_b('a) = DT_CONTRA_NEST_B(unit => dt_contra('a))
-    datatype dt_co_nest_b('a) = DT_CO_NEST_B(unit => dt_co('a))
-    datatype dt_co_twice('a) = DT_CO_TWICE(('a => unit) => 'a)
-    datatype dt_contra_twice('a) = DT_CONTRA_TWICE('a => 'a => unit)
-    datatype dt_a_contra_b_contra('a, 'b) = DT_A_CONTRA_B_CONTRA('a => 'b => unit)
-
-    function f_a_to_a_to_u(_ : Animal) : (Animal => unit) = f_a_to_u
-    function f_a_to_c_to_u(_ : Animal) : (Cat => unit) = f_c_to_u
-    function f_c_to_a_to_u(_ : Cat) : (Animal => unit) = f_a_to_u
-    function f_c_to_c_to_u(_ : Cat) : (Cat => unit) = f_c_to_u
-
-    function f_u_to_u(_ : unit) : unit = ()
-    function f_a_to_u(_ : Animal) : unit = ()
-    function f_c_to_u(_ : Cat) : unit = ()
-
-    function f_dt_contra_a_to_u(_ : dt_contra(Animal)) : unit = ()
-    function f_dt_contra_c_to_u(_ : dt_contra(Cat)) : unit = ()
-    function f_dt_co_a_to_u(_ : dt_co(Animal)) : unit = ()
-    function f_dt_co_c_to_u(_ : dt_co(Cat)) : unit = ()
-    function f_u_to_dt_contra_a(_ : unit) : dt_contra(Animal) = DT_CONTRA(f_a_to_u)
-    function f_u_to_dt_contra_c(_ : unit) : dt_contra(Cat) = DT_CONTRA(f_c_to_u)
-
-    stateful function f_c() : Cat = Chain.create()
-    stateful function f_a() : Animal = f_c()
-
-    stateful function f_u_to_a(_ : unit) : Animal = f_a()
-    stateful function f_u_to_c(_ : unit) : Cat = f_c()
-    stateful function f_a_to_a(_ : Animal) : Animal = f_a()
-    stateful function f_a_to_c(_ : Animal) : Cat = f_c()
-    stateful function f_c_to_a(_ : Cat) : Animal = f_a()
-    stateful function f_c_to_c(_ : Cat) : Cat = f_c()
-
-    stateful function f_a_to_u_to_c(_ : (Animal => unit)) : Cat = f_c()
-    stateful function f_c_to_u_to_a(_ : (Cat => unit)) : Animal = f_a()
-    stateful function f_c_to_u_to_c(_ : (Cat => unit)) : Cat = f_c()
-
-    stateful function f_u_to_dt_co_a(_ : unit) : dt_co(Animal) = DT_CO(f_u_to_a)
-    stateful function f_u_to_dt_co_c(_ : unit) : dt_co(Cat) = DT_CO(f_u_to_c)
-
-    stateful entrypoint init() =
-        let va1 : dt_contra(Animal) = DT_CONTRA(f_a_to_u)  // success
-        let va2 : dt_contra(Animal) = DT_CONTRA(f_c_to_u)  // fail
-        let va3 : dt_contra(Cat)    = DT_CONTRA(f_a_to_u)  // success
-        let va4 : dt_contra(Cat)    = DT_CONTRA(f_c_to_u)  // success
-
-        let vb1 : dt_co(Animal) = DT_CO(f_u_to_a)  // success
-        let vb2 : dt_co(Animal) = DT_CO(f_u_to_c)  // success
-        let vb3 : dt_co(Cat)    = DT_CO(f_u_to_a)  // fail
-        let vb4 : dt_co(Cat)    = DT_CO(f_u_to_c)  // success
-
-        let vc1 : dt_inv(Animal) = DT_INV(f_a_to_a)  // success
-        let vc2 : dt_inv(Animal) = DT_INV(f_a_to_c)  // success
-        let vc3 : dt_inv(Animal) = DT_INV(f_c_to_a)  // fail
-        let vc4 : dt_inv(Animal) = DT_INV(f_c_to_c)  // fail
-        let vc5 : dt_inv(Cat)    = DT_INV(f_a_to_a)  // fail
-        let vc6 : dt_inv(Cat)    = DT_INV(f_a_to_c)  // fail
-        let vc7 : dt_inv(Cat)    = DT_INV(f_c_to_a)  // fail
-        let vc8 : dt_inv(Cat)    = DT_INV(f_c_to_c)  // success
-
-        let vd1 : dt_biv(Animal) = DT_BIV(f_u_to_u) : dt_biv(Animal)  // success
-        let vd2 : dt_biv(Animal) = DT_BIV(f_u_to_u) : dt_biv(Cat)     // success
-        let vd3 : dt_biv(Cat)    = DT_BIV(f_u_to_u) : dt_biv(Animal)  // success
-        let vd4 : dt_biv(Cat)    = DT_BIV(f_u_to_u) : dt_biv(Cat)     // success
-
-        let ve1 : dt_inv_sep(Animal) = DT_INV_SEP_A(f_a_to_u)  // success
-        let ve2 : dt_inv_sep(Animal) = DT_INV_SEP_A(f_c_to_u)  // fail
-        let ve3 : dt_inv_sep(Animal) = DT_INV_SEP_B(f_u_to_a)  // success
-        let ve4 : dt_inv_sep(Animal) = DT_INV_SEP_B(f_u_to_c)  // fail
-        let ve5 : dt_inv_sep(Cat)    = DT_INV_SEP_A(f_a_to_u)  // fail
-        let ve6 : dt_inv_sep(Cat)    = DT_INV_SEP_A(f_c_to_u)  // success
-        let ve7 : dt_inv_sep(Cat)    = DT_INV_SEP_B(f_u_to_a)  // fail
-        let ve8 : dt_inv_sep(Cat)    = DT_INV_SEP_B(f_u_to_c)  // success
-
-        let vf1 : dt_co_nest_a(Animal) = DT_CO_NEST_A(f_dt_contra_a_to_u)  // success
-        let vf2 : dt_co_nest_a(Animal) = DT_CO_NEST_A(f_dt_contra_c_to_u)  // success
-        let vf3 : dt_co_nest_a(Cat)    = DT_CO_NEST_A(f_dt_contra_a_to_u)  // fail
-        let vf4 : dt_co_nest_a(Cat)    = DT_CO_NEST_A(f_dt_contra_c_to_u)  // success
-
-        let vg1 : dt_contra_nest_a(Animal) = DT_CONTRA_NEST_A(f_dt_co_a_to_u)  // success
-        let vg2 : dt_contra_nest_a(Animal) = DT_CONTRA_NEST_A(f_dt_co_c_to_u)  // fail
-        let vg3 : dt_contra_nest_a(Cat)    = DT_CONTRA_NEST_A(f_dt_co_a_to_u)  // success
-        let vg4 : dt_contra_nest_a(Cat)    = DT_CONTRA_NEST_A(f_dt_co_c_to_u)  // success
-
-        let vh1 : dt_contra_nest_b(Animal) = DT_CONTRA_NEST_B(f_u_to_dt_contra_a)  // success
-        let vh2 : dt_contra_nest_b(Animal) = DT_CONTRA_NEST_B(f_u_to_dt_contra_c)  // fail
-        let vh3 : dt_contra_nest_b(Cat)    = DT_CONTRA_NEST_B(f_u_to_dt_contra_a)  // success
-        let vh4 : dt_contra_nest_b(Cat)    = DT_CONTRA_NEST_B(f_u_to_dt_contra_c)  // success
-
-        let vi1 : dt_co_nest_b(Animal) = DT_CO_NEST_B(f_u_to_dt_co_a)  // success
-        let vi2 : dt_co_nest_b(Animal) = DT_CO_NEST_B(f_u_to_dt_co_c)  // success
-        let vi3 : dt_co_nest_b(Cat)    = DT_CO_NEST_B(f_u_to_dt_co_a)  // fail
-        let vi4 : dt_co_nest_b(Cat)    = DT_CO_NEST_B(f_u_to_dt_co_c)  // success
-
-        let vj1 : dt_co_twice(Animal) = DT_CO_TWICE(f_a_to_u_to_c : (Animal => unit) => Animal) : dt_co_twice(Animal)  // success
-        let vj2 : dt_co_twice(Animal) = DT_CO_TWICE(f_c_to_u_to_c : (Cat    => unit) => Cat   ) : dt_co_twice(Cat)     // success
-        let vj3 : dt_co_twice(Cat)    = DT_CO_TWICE(f_c_to_u_to_a : (Animal => unit) => Animal) : dt_co_twice(Animal)  // fail
-        let vj4 : dt_co_twice(Cat)    = DT_CO_TWICE(f_c_to_u_to_c : (Cat    => unit) => Cat   ) : dt_co_twice(Cat)     // success
-
-        let vk01 : dt_a_contra_b_contra(Animal, Animal) = DT_A_CONTRA_B_CONTRA(f_a_to_a_to_u)  // success
-        let vk02 : dt_a_contra_b_contra(Animal, Animal) = DT_A_CONTRA_B_CONTRA(f_a_to_c_to_u)  // fail
-        let vk03 : dt_a_contra_b_contra(Animal, Animal) = DT_A_CONTRA_B_CONTRA(f_c_to_a_to_u)  // fail
-        let vk04 : dt_a_contra_b_contra(Animal, Animal) = DT_A_CONTRA_B_CONTRA(f_c_to_c_to_u)  // fail
-        let vk05 : dt_a_contra_b_contra(Animal, Cat)    = DT_A_CONTRA_B_CONTRA(f_a_to_a_to_u)  // success
-        let vk06 : dt_a_contra_b_contra(Animal, Cat)    = DT_A_CONTRA_B_CONTRA(f_a_to_c_to_u)  // success
-        let vk07 : dt_a_contra_b_contra(Animal, Cat)    = DT_A_CONTRA_B_CONTRA(f_c_to_a_to_u)  // fail
-        let vk08 : dt_a_contra_b_contra(Animal, Cat)    = DT_A_CONTRA_B_CONTRA(f_c_to_c_to_u)  // fail
-        let vk09 : dt_a_contra_b_contra(Cat, Animal)    = DT_A_CONTRA_B_CONTRA(f_a_to_a_to_u)  // success
-        let vk10 : dt_a_contra_b_contra(Cat, Animal)    = DT_A_CONTRA_B_CONTRA(f_a_to_c_to_u)  // fail
-        let vk11 : dt_a_contra_b_contra(Cat, Animal)    = DT_A_CONTRA_B_CONTRA(f_c_to_a_to_u)  // success
-        let vk12 : dt_a_contra_b_contra(Cat, Animal)    = DT_A_CONTRA_B_CONTRA(f_c_to_c_to_u)  // fail
-        let vk13 : dt_a_contra_b_contra(Cat, Cat)       = DT_A_CONTRA_B_CONTRA(f_a_to_a_to_u)  // success
-        let vk14 : dt_a_contra_b_contra(Cat, Cat)       = DT_A_CONTRA_B_CONTRA(f_a_to_c_to_u)  // success
-        let vk15 : dt_a_contra_b_contra(Cat, Cat)       = DT_A_CONTRA_B_CONTRA(f_c_to_a_to_u)  // success
-        let vk16 : dt_a_contra_b_contra(Cat, Cat)       = DT_A_CONTRA_B_CONTRA(f_c_to_c_to_u)  // success
-
-        let vl1 : dt_contra_twice(Animal) = DT_CONTRA_TWICE(f_a_to_a_to_u : Animal => Animal => unit) : dt_contra_twice(Animal)  // success
-        let vl2 : dt_contra_twice(Animal) = DT_CONTRA_TWICE(f_a_to_c_to_u : Cat    => Cat    => unit) : dt_contra_twice(Cat)     // fail
-        let vl3 : dt_contra_twice(Cat)    = DT_CONTRA_TWICE(f_a_to_a_to_u : Animal => Animal => unit) : dt_contra_twice(Animal)  // success
-        let vl4 : dt_contra_twice(Cat)    = DT_CONTRA_TWICE(f_c_to_a_to_u : Cat    => Cat    => unit) : dt_contra_twice(Cat)     // success
-
-        ()

test/contracts/polymorphism_variance_switching_oracles.aes

@@ -1,47 +0,0 @@
-contract interface Animal =
-    entrypoint sound : () => string
-
-contract Cat : Animal =
-    entrypoint sound() = "meow"
-
-main contract Main =
-    entrypoint oracle() = ok_2YNyxd6TRJPNrTcEDCe9ra59SVUdp9FR9qWC5msKZWYD9bP9z5
-
-    entrypoint query() = oq_2oRvyowJuJnEkxy58Ckkw77XfWJrmRgmGaLzhdqb67SKEL1gPY
-
-    entrypoint init() =
-        let o01 : oracle(Animal, Animal) = oracle() : oracle(Animal, Animal)  // success
-        let o02 : oracle(Animal, Animal) = oracle() : oracle(Animal, Cat)     // success
-        let o03 : oracle(Animal, Animal) = oracle() : oracle(Cat, Animal)     // fail
-        let o04 : oracle(Animal, Animal) = oracle() : oracle(Cat, Cat)        // fail
-        let o05 : oracle(Animal, Cat)    = oracle() : oracle(Animal, Animal)  // fail
-        let o06 : oracle(Animal, Cat)    = oracle() : oracle(Animal, Cat)     // success
-        let o07 : oracle(Animal, Cat)    = oracle() : oracle(Cat, Animal)     // fail
-        let o08 : oracle(Animal, Cat)    = oracle() : oracle(Cat, Cat)        // fail
-        let o09 : oracle(Cat, Animal)    = oracle() : oracle(Animal, Animal)  // success
-        let o10 : oracle(Cat, Animal)    = oracle() : oracle(Animal, Cat)     // success
-        let o11 : oracle(Cat, Animal)    = oracle() : oracle(Cat, Animal)     // success
-        let o12 : oracle(Cat, Animal)    = oracle() : oracle(Cat, Cat)        // success
-        let o13 : oracle(Cat, Cat)       = oracle() : oracle(Animal, Animal)  // fail
-        let o14 : oracle(Cat, Cat)       = oracle() : oracle(Animal, Cat)     // success
-        let o15 : oracle(Cat, Cat)       = oracle() : oracle(Cat, Animal)     // fail
-        let o16 : oracle(Cat, Cat)       = oracle() : oracle(Cat, Cat)        // success
-
-        let q01 : oracle_query(Animal, Animal) = query() : oracle_query(Animal, Animal)  // success
-        let q02 : oracle_query(Animal, Animal) = query() : oracle_query(Animal, Cat)     // success
-        let q03 : oracle_query(Animal, Animal) = query() : oracle_query(Cat, Animal)     // success
-        let q04 : oracle_query(Animal, Animal) = query() : oracle_query(Cat, Cat)        // success
-        let q05 : oracle_query(Animal, Cat)    = query() : oracle_query(Animal, Animal)  // fail
-        let q06 : oracle_query(Animal, Cat)    = query() : oracle_query(Animal, Cat)     // success
-        let q07 : oracle_query(Animal, Cat)    = query() : oracle_query(Cat, Animal)     // fail
-        let q08 : oracle_query(Animal, Cat)    = query() : oracle_query(Cat, Cat)        // success
-        let q09 : oracle_query(Cat, Animal)    = query() : oracle_query(Animal, Animal)  // fail
-        let q10 : oracle_query(Cat, Animal)    = query() : oracle_query(Animal, Cat)     // fail
-        let q11 : oracle_query(Cat, Animal)    = query() : oracle_query(Cat, Animal)     // success
-        let q12 : oracle_query(Cat, Animal)    = query() : oracle_query(Cat, Cat)        // success
-        let q13 : oracle_query(Cat, Cat)       = query() : oracle_query(Animal, Animal)  // fail
-        let q14 : oracle_query(Cat, Cat)       = query() : oracle_query(Animal, Cat)     // fail
-        let q15 : oracle_query(Cat, Cat)       = query() : oracle_query(Cat, Animal)     // fail
-        let q16 : oracle_query(Cat, Cat)       = query() : oracle_query(Cat, Cat)        // success
-
-        ()

test/contracts/polymorphism_variance_switching_records.aes

@@ -1,51 +0,0 @@
-contract interface Animal =
-    entrypoint sound : () => string
-
-contract Cat : Animal =
-    entrypoint sound() = "meow"
-
-main contract Main =
-    record rec_co('a)     = { x : 'a ,
-                              y : () => 'a }
-    record rec_contra('a) = { x : 'a => unit }
-    record rec_inv('a)    = { x : 'a => unit,
-                              y : () => 'a }
-    record rec_biv('a)    = { x : int }
-
-    stateful entrypoint new_cat() : Cat = Chain.create()
-    stateful entrypoint new_animal() : Animal = new_cat()
-    stateful entrypoint animal_to_unit(_ : Animal) : unit = ()
-    stateful entrypoint cat_to_unit(_ : Cat) : unit = ()
-    stateful entrypoint unit_to_animal() : Animal = new_animal()
-    stateful entrypoint unit_to_cat() : Cat = new_cat()
-
-    stateful entrypoint init() =
-        let ra  : rec_co(Animal) = { x = new_animal(), y = unit_to_animal }
-        let rc  : rec_co(Cat)    = { x = new_cat(), y = unit_to_cat }
-        let r01 : rec_co(Animal) = ra  // success
-        let r02 : rec_co(Animal) = rc  // success
-        let r03 : rec_co(Cat)    = ra  // fail
-        let r04 : rec_co(Cat)    = rc  // sucess
-
-        let ratu : rec_contra(Animal) = { x = animal_to_unit }
-        let rctu : rec_contra(Cat)    = { x = cat_to_unit }
-        let r05  : rec_contra(Animal) = ratu  // success
-        let r06  : rec_contra(Animal) = rctu  // fail
-        let r07  : rec_contra(Cat)    = ratu  // success
-        let r08  : rec_contra(Cat)    = rctu  // success
-
-        let rxaya : rec_inv(Animal) = { x = animal_to_unit, y = unit_to_animal }
-        let rxcyc : rec_inv(Cat)    = { x = cat_to_unit, y = unit_to_cat }
-        let r09   : rec_inv(Animal) = rxaya  // success
-        let r10   : rec_inv(Animal) = rxcyc  // fail
-        let r11   : rec_inv(Cat)    = rxaya  // fail
-        let r12   : rec_inv(Cat)    = rxcyc  // success
-
-        let rba : rec_biv(Animal) = { x = 1 }
-        let rbc : rec_biv(Cat)    = { x = 1 }
-        let r13 : rec_biv(Animal) = rba  // success
-        let r14 : rec_biv(Animal) = rbc  // success
-        let r15 : rec_biv(Cat)    = rba  // success
-        let r16 : rec_biv(Cat)    = rbc  // success
-
-        ()

test/contracts/test.aes

@@ -1,12 +1,4 @@
-// This is a custom test file if you need to run a compiler without
-// changing aeso_compiler_tests.erl
-
-include "List.aes"
-
-contract IntegerHolder =
-  type state = int
-  entrypoint init(x) = x
-  entrypoint get() = state
-
-main contract Test =
-  stateful entrypoint f(c) = Chain.clone(ref=c, 123)
+contract ShareTwo =                                                                           
+  record state = {s1 : int, s2 : int}                                                         
+  entrypoint init() = {s1 = 0, s2 = 0}                                                        
+  stateful entrypoint buy() = ()

test/contracts/warnings.aes

@@ -48,6 +48,11 @@ contract Warnings =
     rv()
     2
 
+  // Duplicated constraint on 'a
+  entrypoint
+    duplicated_tvar_constraint : 'a is eq, 'a is eq ; ('a, 'a) => bool
+    duplicated_tvar_constraint (x, y) = x == y
+
 namespace FunctionsAsArgs =
     function f() = g()