change approach back to structural, and fix async as well

Author: zth

compiler/ml/dict_type_helpers.ml

@@ -28,17 +28,9 @@
   A dict pattern is treated as a record pattern in the compiler and syntax, with an attriubute `@res.dictPattern`
   attached to it. This attribute is used to tell the compiler that the pattern is a dict pattern, and is what
   triggers the compiler to treat the dict record type differently to regular record types.
-  Dict expressions are lowered to `Primitive_dict.make`, with an internal attribute attached so typing can
-  recognize the construct without depending on the exact lowered callee path.
   *)
 let dict_magic_field_name = "dictValuesType"
 
-let has_dict_literal_attribute attrs =
-  attrs
-  |> List.find_opt (fun (({txt}, _) : Parsetree.attribute) ->
-         txt = "res.$dictLiteral")
-  |> Option.is_some
-
 let has_dict_pattern_attribute attrs =
   attrs
   |> List.find_opt (fun (({txt}, _) : Parsetree.attribute) ->
@@ -55,6 +47,3 @@ let dict_attr : Parsetree.attribute =
 
 let dict_magic_field_attr : Parsetree.attribute =
   (Location.mknoloc "res.$dictMagicField", Parsetree.PStr [])
-
-let dict_literal_attr : Parsetree.attribute =
-  (Location.mknoloc "res.$dictLiteral", Parsetree.PStr [])

compiler/ml/typecore.ml

@@ -2259,6 +2259,19 @@ let extract_function_name funct =
   | Texp_ident (path, _, _) -> Some (Longident.parse (Path.name path))
   | _ -> None
 
+let should_unify_expected_result_before_typing_lowered_apply funct sargs =
+  match (extract_function_name funct, sargs) with
+  | ( Some (Longident.Ldot (Longident.Lident "Primitive_dict", "make")),
+      [(Asttypes.Nolabel, {Parsetree.pexp_desc = Parsetree.Pexp_array _})] ) ->
+    (* Dict literals *)
+    true
+  | ( Some
+        (Longident.Ldot (Longident.Lident "Primitive_promise", "unsafe_async")),
+      [(Asttypes.Nolabel, _)] ) ->
+    (* Async wrapper *)
+    true
+  | _ -> false
+
 type lazy_args =
   (Asttypes.arg_label * (unit -> Typedtree.expression) option) list
 
@@ -2460,9 +2473,11 @@ and type_expect_ ?deprecated_context ~context ?in_function ?(recarg = Rejected)
     let funct =
       type_exp ~deprecated_context:FunctionCall ~context:None env sfunct
     in
-    (if Dict_type_helpers.has_dict_literal_attribute sexp.pexp_attributes then
-       (* Dict literals lower to a regular application, so thread the expected
-          dict value type into the application before typing the tuple values. *)
+    (if should_unify_expected_result_before_typing_lowered_apply funct sargs
+     then
+       (* Lowered syntax like dict literals and async wrappers becomes a regular
+          application, so thread the expected result type into the application
+          before typing its arguments. *)
        let _, ty_res =
          filter_arrow ~env
            ~arity:(Some (List.length sargs))

compiler/syntax/src/res_core.ml

@@ -4324,7 +4324,6 @@ and parse_dict_expr ~start_pos p =
   let key_value_pairs = List.filter_map to_key_value_pair rows in
   Parser.expect Rbrace p;
   Ast_helper.Exp.apply ~loc
-    ~attrs:[Dict_type_helpers.dict_literal_attr]
     (Ast_helper.Exp.ident ~loc
        (Location.mkloc
           (Longident.Ldot (Longident.Lident Primitive_modules.dict, "make"))

compiler/syntax/src/res_parsetree_viewer.ml

@@ -250,7 +250,7 @@ let filter_parsing_attrs attrs =
             Location.txt =
               ( "res.braces" | "ns.braces" | "res.iflet" | "res.ternary"
               | "res.await" | "res.template" | "res.taggedTemplate"
-              | "res.patVariantSpread" | "res.dictPattern" | "res.$dictLiteral"
+              | "res.patVariantSpread" | "res.dictPattern"
               | "res.inlineRecordDefinition" );
           },
           _ ) ->
@@ -585,7 +585,7 @@ let is_printable_attribute attr =
         Location.txt =
           ( "res.iflet" | "res.braces" | "ns.braces" | "JSX" | "res.await"
           | "res.template" | "res.taggedTemplate" | "res.ternary"
-          | "res.$dictLiteral" | "res.inlineRecordDefinition" );
+          | "res.inlineRecordDefinition" );
       },
       _ ) ->
     false

tests/tests/src/DictScopedRecordLiteral.mjs

@@ -9,6 +9,12 @@ let dictValueInference = {
   }
 };
 
+async function asyncValueInference() {
+  return {
+    get: 200
+  };
+}
+
 let primitiveMakeValueInference = {
   health: {
     get: 200
@@ -18,6 +24,7 @@ let primitiveMakeValueInference = {
 export {
   Hidden,
   dictValueInference,
+  asyncValueInference,
   primitiveMakeValueInference,
 }
 /* No side effect */

tests/tests/src/DictScopedRecordLiteral.res

@@ -6,4 +6,8 @@ let dictValueInference: Dict.t<Hidden.routeHandlerObject> = dict{
   "health": {get: 200},
 }
 
+let asyncValueInference: unit => promise<Hidden.routeHandlerObject> = async () => {
+  get: 200,
+}
+
 let primitiveMakeValueInference: Dict.t<Hidden.routeHandlerObject> = dict{"health": {get: 200}}