Pattern guards for functions and switch statements (#339)

* Add case guards to parser

* Add pattern guards to infer types and fcode generation

* Add functions guards

* Add test for patterns guards

* Update docs

* Update CHANGELOG.md

* Remove stateful context from Env for guards

* Elaborate on guards

* Add failing test for stateful pattern guards

* Implement multiple guards

* Fix tests

* Disable aevm related tests

* Split the sentence before if and otherwise

* Fix type in docs

* Implement multiple exprs in the same guard

* Fix pretty printing

* Change tests to include multiple guards

* Add test for non-boolean guards

* Desugar clauses with guards

* Fix incomplete patterns bug

* Fix docs

* Compile to icode when no guards are used

* Revert "Disable aevm related tests"

This reverts commit e828099bd97dffe11438f2e48f3a92ce3641e85b.

test/aeso_calldata_tests.erl

@@ -59,7 +59,7 @@ calldata_aci_test_() ->
         end} || {ContractName, Fun, Args} <- compilable_contracts()].
 
 parse_args(Fun, Args) ->
-    [{contract_main, _, _, [{letfun, _, _, _, _, {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

@@ -202,6 +202,7 @@ compilable_contracts() ->
      "child_contract_init_bug",
      "using_namespace",
      "assign_patterns",
+     "patterns_guards",
      "test" % Custom general-purpose test file. Keep it last on the list.
     ].
 
@@ -808,6 +809,14 @@ failing_contracts() ->
                   [<<?Pos(8,23)
                      "Unbound variable g at line 8, column 23">>
                   ])
+    , ?TYPE_ERROR(stateful_pattern_guard,
+                  [<<?Pos(8,12)
+                     "Cannot reference stateful function g (at line 8, column 12) in a pattern guard.">>
+                  ])
+    , ?TYPE_ERROR(non_boolean_pattern_guard,
+                  [<<?Pos(4,24)
+                     "Cannot unify string\n         and bool\nwhen checking the type of the expression at line 4, column 24\n  \"y\" : string\nagainst the expected type\n  bool">>
+                  ])
     ].
 
 -define(Path(File), "code_errors/" ??File).

test/aeso_parser_tests.erl

@@ -17,7 +17,7 @@ simple_contracts_test_() ->
             ?assertMatch(
                 [{contract_main, _, {con, _, "Identity"},
                     [{letfun, _, {id, _, "id"}, [{id, _, "x"}], {id, _, "_"},
-                        {id, _, "x"}}]}], parse_string(Text)),
+                        [{guarded, _, [], {id, _, "x"}}]}]}], parse_string(Text)),
             ok
        end},
       {"Operator precedence test.",

test/contracts/non_boolean_pattern_guard.aes

@@ -0,0 +1,4 @@
+contract C =
+  type state = int
+
+  entrypoint init(x) | "y" = 1

test/contracts/patterns_guards.aes

@@ -0,0 +1,19 @@
+include "List.aes"
+
+contract C =
+  type state = int
+
+  entrypoint init() = f([1, 2, 3, 4])
+
+  function
+    f(x::[])
+      | x > 1, x < 10 = 1
+      | x < 1 = 9
+    f(x::y::[]) = 2
+    f(x::y::z) = switch(z)
+      [] => 4
+      a::[]
+        | a > 10, a < 20 => 5
+        | a > 5 => 8
+      b | List.length(b) > 5 => 6
+      c => 7

test/contracts/stateful_pattern_guard.aes

@@ -0,0 +1,10 @@
+contract C =
+  type state = int
+
+  entrypoint init() = f(4)
+
+  function
+    f(x) | x > 0 = 1
+    f(x) | g(x) = 2
+
+  stateful function g(x) = x < 0