propagate expected dict value type into dict literal typing

Author: zth

compiler/ml/typecore.ml

@@ -2259,6 +2259,15 @@ let extract_function_name funct =
   | Texp_ident (path, _, _) -> Some (Longident.parse (Path.name path))
   | _ -> None
 
+let is_primitive_dict_make = function
+  | {
+      pexp_desc =
+        Pexp_ident
+          {txt = Longident.Ldot (Longident.Lident "Primitive_dict", "make")};
+    } ->
+    true
+  | _ -> false
+
 type lazy_args =
   (Asttypes.arg_label * (unit -> Typedtree.expression) option) list
 
@@ -2460,6 +2469,15 @@ and type_expect_ ?deprecated_context ~context ?in_function ?(recarg = Rejected)
     let funct =
       type_exp ~deprecated_context:FunctionCall ~context:None env sfunct
     in
+    (if is_primitive_dict_make sfunct then
+       (* Dict literals lower to Primitive_dict.make, so thread the expected
+          dict value type into the application before typing the tuple values. *)
+       let _, ty_res =
+         filter_arrow ~env
+           ~arity:(Some (List.length sargs))
+           funct.exp_type Nolabel
+       in
+       unify_exp_types ~context:None loc env ty_res (instance env ty_expected));
     let ty = instance env funct.exp_type in
     end_def ();
     wrap_trace_gadt_instances env (lower_args env []) ty;

tests/build_tests/super_errors/expected/dict_show_no_coercion.res.expected

@@ -1,15 +1,12 @@
 
   We've found a bug for you!
-  /.../fixtures/dict_show_no_coercion.res:2:23-35
+  /.../fixtures/dict_show_no_coercion.res:2:33-34
 
   1 │ // This should not show coercion suggestion since just the inner types a
     │ re coercable, not the full type + expression (dict<float> -> dict<JSON.t
     │ >)
-  2 │ let x: dict<JSON.t> = dict{"1": 1.}
+  2 │ let x: dict<JSON.t> = dict{"1": 1.}
   3 │ 
 
-  This has type: dict<float>
-  But it's expected to have type: dict<JSON.t>
-  
-  The incompatible parts:
-    float vs JSON.t (defined as JSON.t)
+  This has type: float
+  But it's expected to have type: JSON.t (defined as JSON.t)

tests/tests/src/DictScopedRecordLiteral.mjs

@@ -0,0 +1,23 @@
+// Generated by ReScript, PLEASE EDIT WITH CARE
+
+
+let Hidden = {};
+
+let dictValueInference = {
+  health: {
+    get: 200
+  }
+};
+
+let primitiveMakeValueInference = {
+  health: {
+    get: 200
+  }
+};
+
+export {
+  Hidden,
+  dictValueInference,
+  primitiveMakeValueInference,
+}
+/* No side effect */

tests/tests/src/DictScopedRecordLiteral.res

@@ -0,0 +1,9 @@
+module Hidden = {
+  type routeHandlerObject = {get: int}
+}
+
+let dictValueInference: Dict.t<Hidden.routeHandlerObject> = dict{
+  "health": {get: 200},
+}
+
+let primitiveMakeValueInference: Dict.t<Hidden.routeHandlerObject> = dict{"health": {get: 200}}