Merge pull request #457 from erszcz/fix-map-type-inference

Fix map type inference

src/typechecker.erl

@@ -1544,15 +1544,15 @@ subst_ty(_, Ty) -> Ty.
 %% and the expression to type check.
 %% Returns the type of the expression, a collection of variables bound in
 %% the expression together with their type and constraints.
--spec type_check_expr(env(), expr()) -> {any(), env(), constraints:constraints()}.
+-spec type_check_expr(env(), expr()) -> {type(), env(), constraints:constraints()}.
 type_check_expr(Env, Expr) ->
     Res = {Ty, _VarBinds, _Cs} = do_type_check_expr(Env, Expr),
     ?verbose(Env, "~sPropagated type of ~ts :: ~ts~n",
              [gradualizer_fmt:format_location(Expr, brief), erl_prettypr:format(Expr), typelib:pp_type(Ty)]),
     Res.
 
 %% TODO: move tenv to back
--spec do_type_check_expr(env(), expr()) -> {any(), env(), constraints:constraints()}.
+-spec do_type_check_expr(env(), expr()) -> {type(), env(), constraints:constraints()}.
 do_type_check_expr(Env, {var, _P, Var}) ->
     case Env#env.venv of
         #{Var := Ty} ->
@@ -1714,10 +1714,10 @@ do_type_check_expr(#env{infer = true} = Env, {float, _, _F}) ->
 %% Maps
 do_type_check_expr(Env, {map, _, Assocs}) ->
     {AssocTys, VB, Cs} = type_check_assocs(Env, Assocs),
-    % TODO: When the --infer flag is set we should return the type of the map
     case Env#env.infer of
         true ->
-            {type(map, AssocTys), VB, Cs};
+            MapTy = update_map_type(type(map, []), AssocTys),
+            {MapTy, VB, Cs};
         false ->
             {type(any), VB, Cs}
     end;

test/should_fail/covariant_map_keys_fail.erl

@@ -1,13 +1,9 @@
 -module(covariant_map_keys_fail).
 
--compile([nowarn_unused_function]).
 -export([not_good/1]).
 
--spec good(#{ good := A }) -> A.
-good(#{ good := X }) -> X.
+-spec good(#{good := A}) -> A.
+good(#{good := X}) -> X.
 
 -spec not_good(#{good | bad := A}) -> A.
 not_good(M) -> good(M). %% This call should fail
-
--spec kaboom() -> integer().
-kaboom() -> not_good(#{ bad => 0 }).

test/should_pass/map_creation.erl

@@ -1,5 +1,5 @@
 -module(map_creation).
--export([f/0, g/0]).
+-export([f/0, g/0, h/0]).
 
 -spec f() -> #{apa := bepa}.
 f() -> #{apa => bepa}.
@@ -9,3 +9,6 @@ f() -> #{apa => bepa}.
 -spec g() -> typed_map().
 g() ->
     #{field_a => <<"ala ma kota">>}.
+
+-spec h() -> #{inner := #{a := 5}}.
+h() -> #{inner => #{a => 5}}.

test/should_pass/map_infer_pass.erl

@@ -0,0 +1,19 @@
+-module(map_infer_pass).
+
+-export([not_good/1,
+         kaboom1/0,
+         kaboom2/0]).
+
+-gradualizer([infer]).
+
+-spec not_good(#{good | bad := integer()}) -> integer().
+not_good(#{good := _}) -> 0.
+
+-spec kaboom1() -> integer().
+kaboom1() ->
+    M = #{bad => 0},
+    not_good(M).
+
+-spec kaboom2() -> integer().
+kaboom2() ->
+    not_good(#{bad => 0}).