Implement loading namespaces with the using keyword (#338)

* Add using namespace as to scanner and parser

* Change the alias from id() to con()

* Add using namespace to AST type inference

* Allow using namespace to appear in the top level

* Allow using namespace to appear inside functions

* Add a compiler test for using namespace

* Handle name collisions

* Implement mk_error for ambiguous_name

* Add failing test for ambiguous names

* Limit the scope of the used namespaces

* Add test for wrong scope of using namespace

* Use a single using declaration

* Split long line

* Forbid using undefined namespaces

* Add a test for using undefined namespaces

* Change the type of used_namespaces

* Add using namespace parts to scanner and parser

* Add using namespace parts to ast type inference

* Add tests for using namespace parts

* Update CHANGELOG.md

* Code cleaning

* Update the docs

* Update the docs about the same alias for multiple namespaces

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - `Set` stdlib
 - `Option.force_msg`
+- Loading namespaces into the current scope (e.g. `using Pair`)
 ### Changed
 ### Removed
 

docs/sophia_features.md

@@ -248,6 +248,66 @@ Functions in namespaces have access to the same environment (including the
 with the exception of `state`, `put` and `Chain.event` since these are
 dependent on the specific state and event types of the contract.
 
+To avoid mentioning the namespace every time it is used, Sophia allows
+including the namespace in the current scope with the `using` keyword:
+```
+include "Pair.aes"
+using Pair
+contract C =
+  type state = int
+  entrypoint init() =
+    let p = (1, 2)
+    fst(p)  // this is the same as Pair.fst(p)
+```
+
+It is also possible to make an alias for the namespace with the `as` keyword:
+```
+include "Pair.aes"
+contract C =
+  using Pair as P
+  type state = int
+  entrypoint init() =
+    let p = (1, 2)
+    P.fst(p)  // this is the same as Pair.fst(p)
+```
+
+Having the same alias for multiple namespaces is possible and it allows
+referening functions that are defined in different namespaces and have
+different names with the same alias:
+```
+namespace Xa = function f() = 1
+namespace Xb = function g() = 2
+contract Cntr =
+  using Xa as A
+  using Xb as A
+  type state = int
+  entrypoint init() = A.f() + A.g()
+```
+
+Note that using functions with the same name would result in an ambiguous name
+error:
+```
+namespace Xa = function f() = 1
+namespace Xb = function f() = 2
+contract Cntr =
+  using Xa as A
+  using Xb as A
+  type state = int
+
+  // the next line has an error because f is defined in both Xa and Xb
+  entrypoint init() = A.f()
+```
+
+Importing specific parts of a namespace or hiding these parts can also be
+done like this:
+```
+using Pair for [fst, snd]       // this will only import fst and snd
+using Triple hiding [fst, snd]  // this will import everything except for fst and snd
+```
+
+Note that it is possible to use a namespace in the top level of the file, in the
+contract level, namespace level, or in the function level.
+
 ## Splitting code over multiple files
 
 Code from another file can be included in a contract using an `include`

src/aeso_ast_infer_types.erl

@@ -102,6 +102,10 @@
 -type qname() :: [string()].
 -type typesig() :: {type_sig, aeso_syntax:ann(), type_constraints(), [aeso_syntax:named_arg_t()], [type()], type()}.
 
+-type namespace_alias() :: none | name().
+-type namespace_parts() :: none | {for, [name()]} | {hiding, [name()]}.
+-type used_namespaces() :: [{qname(), namespace_alias(), namespace_parts()}].
+
 -type type_constraints() :: none | bytes_concat | bytes_split | address_to_contract | bytecode_hash.
 
 -type fun_info()  :: {aeso_syntax:ann(), typesig() | type()}.
@@ -126,6 +130,7 @@
     , typevars         = unrestricted       :: unrestricted | [name()]
     , fields           = #{}                :: #{ name() => [field_info()] }    %% fields are global
     , namespace        = []                 :: qname()
+    , used_namespaces  = []                 :: used_namespaces()
     , in_pattern       = false              :: boolean()
     , stateful         = false              :: boolean()
     , current_function = none               :: none | aeso_syntax:id()
@@ -312,9 +317,38 @@ bind_contract({Contract, Ann, Id, Contents}, Env)
 
 %% What scopes could a given name come from?
 -spec possible_scopes(env(), qname()) -> [qname()].
-possible_scopes(#env{ namespace = Current}, Name) ->
+possible_scopes(#env{ namespace = Current, used_namespaces = UsedNamespaces }, Name) ->
     Qual = lists:droplast(Name),
-    [ lists:sublist(Current, I) ++ Qual || I <- lists:seq(0, length(Current)) ].
+    NewQuals = case lists:filter(fun(X) -> element(2, X) == Qual end, UsedNamespaces) of
+                   [] ->
+                       [Qual];
+                   Namespaces ->
+                       lists:map(fun(X) -> element(1, X) end, Namespaces)
+               end,
+    Ret1 = [ lists:sublist(Current, I) ++ Q || I <- lists:seq(0, length(Current)), Q <- NewQuals ],
+    Ret2 = [ Namespace ++ Q || {Namespace, none, _} <- UsedNamespaces, Q <- NewQuals ],
+    lists:usort(Ret1 ++ Ret2).
+
+-spec visible_in_used_namespaces(used_namespaces(), qname()) -> boolean().
+visible_in_used_namespaces(UsedNamespaces, QName) ->
+    Qual = lists:droplast(QName),
+    Name = lists:last(QName),
+    case lists:filter(fun({Ns, _, _}) -> Qual == Ns end, UsedNamespaces) of
+        [] ->
+            true;
+        Namespaces ->
+            IsVisible = fun(Namespace) ->
+                            case Namespace of
+                                {_, _, {for, Names}} ->
+                                    lists:member(Name, Names);
+                                {_, _, {hiding, Names}} ->
+                                    not lists:member(Name, Names);
+                                _ ->
+                                    true
+                            end
+                        end,
+            lists:any(IsVisible, Namespaces)
+    end.
 
 -spec lookup_type(env(), type_id()) -> false | {qname(), type_info()}.
 lookup_type(Env, Id) ->
@@ -341,7 +375,7 @@ lookup_env(Env, Kind, Ann, Name) ->
     end.
 
 -spec lookup_env1(env(), type | term, aeso_syntax:ann(), qname()) -> false | {qname(), fun_info()}.
-lookup_env1(#env{ namespace = Current, scopes = Scopes }, Kind, Ann, QName) ->
+lookup_env1(#env{ namespace = Current, used_namespaces = UsedNamespaces, scopes = Scopes }, Kind, Ann, QName) ->
     Qual = lists:droplast(QName),
     Name = lists:last(QName),
     AllowPrivate = lists:prefix(Qual, Current),
@@ -365,8 +399,12 @@ lookup_env1(#env{ namespace = Current, scopes = Scopes }, Kind, Ann, QName) ->
                 {Ann1, _} = E ->
                     %% Check that it's not private (or we can see private funs)
                     case not is_private(Ann1) orelse AllowPrivate of
+                        true  ->
+                            case visible_in_used_namespaces(UsedNamespaces, QName) of
                                 true -> {QName, E};
                                 false -> false
+                            end;
+                        false -> false
                     end
             end
     end.
@@ -803,6 +841,8 @@ infer1(Env, [{namespace, Ann, Name, Code} | Rest], Acc, Options) ->
     {Env1, Code1} = infer_contract_top(push_scope(namespace, Name, Env), namespace, Code, Options),
     Namespace1 = {namespace, Ann, Name, Code1},
     infer1(pop_scope(Env1), Rest, [Namespace1 | Acc], Options);
+infer1(Env, [Using = {using, _, _, _, _} | Rest], Acc, Options) ->
+    infer1(check_usings(Env, Using), Rest, Acc, Options);
 infer1(Env, [{pragma, _, _} | Rest], Acc, Options) ->
     %% Pragmas are checked in check_modifiers
     infer1(Env, Rest, Acc, Options).
@@ -859,10 +899,13 @@ infer_contract(Env0, What, Defs0, Options) ->
               ({letfun, _, _, _, _, _})   -> function;
               ({fun_clauses, _, _, _, _}) -> function;
               ({fun_decl, _, _, _})       -> prototype;
+              ({using, _, _, _, _})       -> using;
               (_)                         -> unexpected
            end,
     Get = fun(K, In) -> [ Def || Def <- In, Kind(Def) == K ] end,
-    {Env1, TypeDefs} = check_typedefs(Env, Get(type, Defs)),
+    OldUsedNamespaces = Env#env.used_namespaces,
+    Env01 = check_usings(Env, Get(using, Defs)),
+    {Env1, TypeDefs} = check_typedefs(Env01, Get(type, Defs)),
     create_type_errors(),
     check_unexpected(Get(unexpected, Defs)),
     Env2 =
@@ -884,11 +927,13 @@ infer_contract(Env0, What, Defs0, Options) ->
     DepGraph  = maps:map(fun(_, Def) -> aeso_syntax_utils:used_ids(Def) end, FunMap),
     SCCs      = aeso_utils:scc(DepGraph),
     {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
     check_state_dependencies(Env4, Defs1),
     destroy_and_report_type_errors(Env4),
     %% Add inferred types of definitions
-    {Env4, TypeDefs ++ Decls ++ Defs1}.
+    {Env5, TypeDefs ++ Decls ++ Defs1}.
 
 %% Restructure blocks into multi-clause fundefs (`fun_clauses`).
 -spec process_blocks([aeso_syntax:decl()]) -> [aeso_syntax:decl()].
@@ -988,6 +1033,43 @@ check_typedef(Env, {variant_t, Cons}) ->
     {variant_t, [ {constr_t, Ann, Con, [ check_type(Env, Arg) || Arg <- Args ]}
                 || {constr_t, Ann, Con, Args} <- Cons ]}.
 
+check_usings(Env, []) ->
+    Env;
+check_usings(Env = #env{ used_namespaces = UsedNamespaces }, [{using, Ann, Con, Alias, Parts} | Rest]) ->
+    AliasName = case Alias of
+                    none ->
+                        none;
+                    _ ->
+                        qname(Alias)
+                end,
+    case get_scope(Env, qname(Con)) of
+        false ->
+            create_type_errors(),
+            type_error({using_undefined_namespace, Ann, qname(Con)}),
+            destroy_and_report_type_errors(Env);
+        Scope ->
+            Nsp = case Parts of
+                      none ->
+                          {qname(Con), AliasName, none};
+                      {ForOrHiding, Ids} ->
+                          IsUndefined = fun(Id) ->
+                                            proplists:lookup(name(Id), Scope#scope.funs) == none
+                                        end,
+                          UndefinedIds = lists:filter(IsUndefined, Ids),
+                          case UndefinedIds of
+                              [] ->
+                                  {qname(Con), AliasName, {ForOrHiding, lists:map(fun name/1, Ids)}};
+                              _ ->
+                                  create_type_errors(),
+                                  type_error({using_undefined_namespace_parts, Ann, qname(Con), lists:map(fun qname/1, UndefinedIds)}),
+                                  destroy_and_report_type_errors(Env)
+                          end
+                  end,
+            check_usings(Env#env{ used_namespaces = UsedNamespaces ++ [Nsp] }, Rest)
+    end;
+check_usings(Env, Using = {using, _, _, _, _}) ->
+    check_usings(Env, [Using]).
+
 check_unexpected(Xs) ->
     [ type_error(X) || X <- Xs ].
 
@@ -1017,6 +1099,8 @@ check_modifiers_(Env, [{namespace, _, _, Decls} | Rest]) ->
 check_modifiers_(Env, [{pragma, Ann, Pragma} | Rest]) ->
     check_pragma(Env, Ann, Pragma),
     check_modifiers_(Env, Rest);
+check_modifiers_(Env, [{using, _, _, _, _} | Rest]) ->
+    check_modifiers_(Env, Rest);
 check_modifiers_(Env, [Decl | Rest]) ->
     type_error({bad_top_level_decl, Decl}),
     check_modifiers_(Env, Rest);
@@ -1770,6 +1854,8 @@ infer_block(Env, _, [{letval, Attrs, Pattern, E}|Rest], BlockType) ->
     {'case', _, NewPattern, {typed, _, {block, _, NewRest}, _}} =
         infer_case(Env, Attrs, Pattern, PatType, {block, Attrs, Rest}, BlockType),
     [{letval, Attrs, NewPattern, NewE}|NewRest];
+infer_block(Env, Attrs, [Using = {using, _, _, _, _} | Rest], BlockType) ->
+    infer_block(check_usings(Env, Using), Attrs, Rest, BlockType);
 infer_block(Env, Attrs, [E|Rest], BlockType) ->
     [infer_expr(Env, E)|infer_block(Env, Attrs, Rest, BlockType)].
 
@@ -2987,6 +3073,17 @@ mk_error({contract_lacks_definition, Type, When}) ->
            ),
     {Pos, Ctxt} = pp_when(When),
     mk_t_err(Pos, Msg, Ctxt);
+mk_error({ambiguous_name, QIds = [{qid, Ann, _} | _]}) ->
+    Names = lists:map(fun(QId) -> io_lib:format("~s at ~s\n", [pp(QId), pp_loc(QId)]) end, QIds),
+    Msg = "Ambiguous name: " ++ lists:concat(Names),
+    mk_t_err(pos(Ann), Msg);
+mk_error({using_undefined_namespace, Ann, Namespace}) ->
+    Msg = io_lib:format("Cannot use undefined namespace ~s", [Namespace]),
+    mk_t_err(pos(Ann), Msg);
+mk_error({using_undefined_namespace_parts, Ann, Namespace, Parts}) ->
+    PartsStr = lists:concat(lists:join(", ", Parts)),
+    Msg = io_lib:format("The namespace ~s does not define the following names: ~s", [Namespace, PartsStr]),
+    mk_t_err(pos(Ann), Msg);
 mk_error(Err) ->
     Msg = io_lib:format("Unknown error: ~p\n", [Err]),
     mk_t_err(pos(0, 0), Msg).

src/aeso_parser.erl

@@ -109,6 +109,7 @@ decl() ->
 
     , ?RULE(keyword(namespace), con(), tok('='), maybe_block(decl()), {namespace, _1, _2, _4})
     , ?RULE(keyword(include),   str(), {include, get_ann(_1), _2})
+    , using()
     , pragma()
 
       %% Type declarations  TODO: format annotation for "type bla" vs "type bla()"
@@ -135,6 +136,21 @@ fundef_or_decl() ->
     choice([?RULE(id(), tok(':'), type(), {fun_decl, get_ann(_1), _1, _3}),
             fundef()]).
 
+using() ->
+    Alias = {keyword(as), con()},
+    For = ?RULE(keyword(for), bracket_list(id()), {for, _2}),
+    Hiding = ?RULE(keyword(hiding), bracket_list(id()), {hiding, _2}),
+    ?RULE(keyword(using), con(), optional(Alias), optional(choice(For, Hiding)), using(get_ann(_1), _2, _3, _4)).
+
+using(Ann, Con, none, none) ->
+    {using, Ann, Con, none, none};
+using(Ann, Con, {ok, {_, Alias}}, none) ->
+    {using, Ann, Con, Alias, none};
+using(Ann, Con, none, {ok, List}) ->
+    {using, Ann, Con, none, List};
+using(Ann, Con, {ok, {_, Alias}}, {ok, List}) ->
+    {using, Ann, Con, Alias, List}.
+
 pragma() ->
     Op = choice([token(T) || T <- ['<', '=<', '==', '>=', '>']]),
     ?RULE(tok('@'), id("compiler"), Op, version(), {pragma, get_ann(_1), {compiler, element(1, _3), _4}}).
@@ -254,7 +270,8 @@ body() ->
 
 stmt() ->
     ?LAZY_P(choice(
-    [ expr()
+    [ using()
+    , expr()
     , letdecl()
     , {switch, keyword(switch), parens(expr()), maybe_block(branch())}
     , {'if', keyword('if'), parens(expr()), body()}

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"
+                "interface", "main", "using", "as", "for", "hiding"
                ],
     KW = string:join(Keywords, "|"),
 

src/aeso_syntax.erl

@@ -35,6 +35,9 @@
 -type qcon() :: {qcon, ann(), [name()]}.
 -type tvar() :: {tvar, ann(), name()}.
 
+-type namespace_alias() :: none | con().
+-type namespace_parts() :: none | {for, [id()]} | {hiding, [id()]}.
+
 -type decl() :: {contract_main, ann(), con(), [decl()]}
               | {contract_child, ann(), con(), [decl()]}
               | {contract_interface, ann(), con(), [decl()]}
@@ -44,6 +47,7 @@
               | {type_def, ann(), id(), [tvar()], typedef()}
               | {fun_clauses, ann(), id(), type(), [letfun() | fundecl()]}
               | {block, ann(), [decl()]}
+              | {using, ann(), con(), namespace_alias(), namespace_parts()}
               | fundecl()
               | letfun()
               | letval(). % Only for error msgs
@@ -52,7 +56,6 @@
 
 -type pragma() :: {compiler, '==' | '<' | '>' | '=<' | '>=', compiler_version()}.
 
-
 -type letval()  :: {letval, ann(), pat(), expr()}.
 -type letfun()  :: {letfun, ann(), id(), [pat()], type(), expr()}.
 -type fundecl() :: {fun_decl, ann(), id(), type()}.

test/aeso_compiler_tests.erl

@@ -200,6 +200,7 @@ compilable_contracts() ->
      "clone_simple",
      "create",
      "child_contract_init_bug",
+     "using_namespace",
      "test" % Custom general-purpose test file. Keep it last on the list.
     ].
 
@@ -781,6 +782,30 @@ failing_contracts() ->
                    [<<?Pos(1,6)
                       "Only one main contract can be defined.">>
                    ])
+    , ?TYPE_ERROR(using_namespace_ambiguous_name,
+                  [ <<?Pos(2,3)
+                      "Ambiguous name: Xa.f at line 2, column 3\nXb.f at line 5, column 3">>
+                  , <<?Pos(13,23)
+                      "Unbound variable A.f at line 13, column 23">>
+                  ])
+    , ?TYPE_ERROR(using_namespace_wrong_scope,
+                  [ <<?Pos(19,5)
+                      "Unbound variable f at line 19, column 5">>
+                  , <<?Pos(21,23)
+                      "Unbound variable f at line 21, column 23">>
+                  ])
+    , ?TYPE_ERROR(using_namespace_undefined,
+                  [<<?Pos(2,3)
+                     "Cannot use undefined namespace MyUndefinedNamespace">>
+                  ])
+    , ?TYPE_ERROR(using_namespace_undefined_parts,
+                  [<<?Pos(5,3)
+                     "The namespace Nsp does not define the following names: a">>
+                  ])
+    , ?TYPE_ERROR(using_namespace_hidden_parts,
+                  [<<?Pos(8,23)
+                     "Unbound variable g at line 8, column 23">>
+                  ])
     ].
 
 -define(Path(File), "code_errors/" ??File).

test/contracts/using_namespace.aes

@@ -0,0 +1,36 @@
+include "Option.aes"
+include "Pair.aes"
+include "String.aes"
+include "Triple.aes"
+
+using Pair
+using Triple hiding [fst, snd]
+
+namespace Nsp =
+  using Option
+
+  function h() =
+    let op = Some((2, 3, 4))
+    if (is_some(op))
+      thd(force(op)) == 4
+    else
+      false
+
+contract Cntr =
+  using Nsp
+
+  entrypoint init() = ()
+
+  function f() =
+    let p = (1, 2)
+    if (h())
+      fst(p)
+    else
+      snd(p)
+
+  function g() =
+    using String for [concat]
+
+    let s1 = "abc"
+    let s2 = "def"
+    concat(s1, s2)

test/contracts/using_namespace_ambiguous_name.aes

@@ -0,0 +1,13 @@
+namespace Xa =
+  function f() = 1
+
+namespace Xb =
+  function f() = 2
+
+contract Cntr =
+  using Xa as A
+  using Xb as A
+
+  type state = int
+
+  entrypoint init() = A.f()

test/contracts/using_namespace_hidden_parts.aes

@@ -0,0 +1,8 @@
+namespace Nsp =
+  function f() = 1
+  function g() = 2
+
+contract Cntr =
+  using Nsp for [f]
+
+  entrypoint init() = g()

test/contracts/using_namespace_undefined.aes

@@ -0,0 +1,4 @@
+contract C =
+  using MyUndefinedNamespace
+
+  entrypoint init() = ()

test/contracts/using_namespace_undefined_parts.aes

@@ -0,0 +1,7 @@
+namespace Nsp =
+  function f() = 1
+
+contract Cntr =
+  using Nsp for [a]
+
+  entrypoint init() = f()

test/contracts/using_namespace_wrong_scope.aes

@@ -0,0 +1,21 @@
+namespace Nsp1 =
+  function f() = 1
+
+namespace Nsp2 =
+  using Nsp1
+
+  function g() = 1
+
+contract Cntr =
+  using Nsp2
+
+  type state = int
+
+  function x() =
+    using Nsp1
+    f()
+
+  function y() =
+    f()
+
+  entrypoint init() = f()