no need to check tvar

Author: zth

jscomp/build_tests/super_errors/expected/dict_pattern_regular_record.res.expected

@@ -0,0 +1,25 @@
+
+  Warning number 9
+  /.../fixtures/dict_pattern_regular_record.res:5:22-33
+
+  3 │ let constrainedAsDict = (dict: x) =>
+  4 │   switch dict {
+  5 │   | @res.dictPattern {one: "one"} => Js.log("one")
+  6 │   | _ => Js.log("not one")
+  7 │   }
+
+  the following labels are not bound in this record pattern: dictValuesType
+Either bind these labels explicitly or add ', _' to the pattern.
+
+
+  We've found a bug for you!
+  /.../fixtures/dict_pattern_regular_record.res:5:22-33
+
+  3 │ let constrainedAsDict = (dict: x) =>
+  4 │   switch dict {
+  5 │   | @res.dictPattern {one: "one"} => Js.log("one")
+  6 │   | _ => Js.log("not one")
+  7 │   }
+
+  This pattern matches values of type dict<string>
+  but a pattern was expected which matches values of type x

jscomp/build_tests/super_errors/fixtures/dict_pattern_regular_record.res

@@ -0,0 +1,7 @@
+type x = {one: int}
+
+let constrainedAsDict = (dict: x) =>
+  switch dict {
+  | @res.dictPattern {one: "one"} => Js.log("one")
+  | _ => Js.log("not one")
+  }

jscomp/ml/typecore.ml

@@ -1386,13 +1386,12 @@ and type_pat_aux ~constrs ~labels ~no_existentials ~mode ~explode ~env
   | Ppat_record(lid_sp_list, closed) ->
       let has_dict_pattern_attr = Dict_type_helpers.has_dict_pattern_attribute sp.ppat_attributes in
       let opath, record_ty = (
-      match (has_dict_pattern_attr, expected_ty.desc) with 
-      | (true, Tvar _) -> 
+      if has_dict_pattern_attr then (
         (* When this is a dict pattern and we don't have an actual expected type yet, 
          infer the type as a dict with a new type variable. This let us hook into the 
          existing inference mechanism for records in dict pattern matching too. *)
         (Some (Predef.path_dict, Predef.path_dict), newgenty (Tconstr (Predef.path_dict, [newvar ()], ref Mnil)))
-      | _ ->
+      ) else
         try
           let (p0, p, _, _) = extract_concrete_record !env expected_ty in
           Some (p0, p), expected_ty