Conditionally print message about record possibly being component

CHANGELOG.md

@@ -20,6 +20,9 @@
 
 - `$$default` is no longer exported from the generated JavaScript when using default exports. https://github.com/rescript-lang/rescript-compiler/pull/6328
 
+#### :nail_care: Polish
+- Conditionally print error message about record with missing label potentially being a component. https://github.com/rescript-lang/rescript-compiler/pull/6337
+
 # 11.0.0-beta.4
 
 #### :rocket: New Feature

jscomp/build_tests/super_errors/expected/component_missing_prop.res.expected

@@ -0,0 +1,12 @@
+
+  We've found a bug for you!
+  /.../fixtures/component_missing_prop.res:5:34-35
+
+  3 │   type props<'name> = {name: 'name}
+  4 │ 
+  5 │   let make = (): props<'name> => {}
+  6 │ }
+  7 │ 
+
+  Some required record fields are missing:
+  name. If this is a component, add the missing props.

jscomp/build_tests/super_errors/expected/variant_spread_inline_records.res.expected

@@ -6,5 +6,4 @@
   3 │ 
   4 │ let b: b = One({name: "hello"})
 
-  Some required record fields are missing:
-  age. If this is a component, add the missing props.
+  Some required record fields are missing: age.

jscomp/build_tests/super_errors/fixtures/component_missing_prop.res

@@ -0,0 +1,6 @@
+// Since the React transform isn't active in the tests, mimic what the transform outputs.
+module Component = {
+  type props<'name> = {name: 'name}
+
+  let make = (): props<'name> => {}
+}

jscomp/ml/typecore.ml

@@ -35,7 +35,7 @@ type error =
   | Apply_non_function of type_expr
   | Apply_wrong_label of arg_label * type_expr
   | Label_multiply_defined of string
-  | Labels_missing of string list
+  | Labels_missing of string list * bool
   | Label_not_mutable of Longident.t
   | Wrong_name of string * type_expr * string * Path.t * string * string list
   | Name_type_mismatch of
@@ -1963,6 +1963,11 @@ let rec lower_args env seen ty_fun  =
 let not_function env ty =
   let ls, tvar = list_labels env ty in
   ls = [] && not tvar
+
+let check_might_be_component env ty_record =
+  match (expand_head env ty_record).desc with 
+  | Tconstr (path, _, _) when path |> Path.last = "props" -> true 
+  | _ -> false
 
 type lazy_args = 
   (Asttypes.arg_label * (unit -> Typedtree.expression) option) list
@@ -2299,8 +2304,9 @@ and type_expect_ ?in_function ?(recarg=Rejected) env sexp ty_expected =
               else
                 Some name in
             let labels_missing = fields |> List.filter_map filter_missing in
-            if labels_missing <> [] then
-              raise(Error(loc, env, Labels_missing labels_missing));
+            if labels_missing <> [] then (
+              let might_be_component = check_might_be_component env ty_record in
+              raise(Error(loc, env, Labels_missing (labels_missing, might_be_component))));
             [||], representation
         | [], _ ->
           if fields = [] && repr_opt <> None then
@@ -2324,8 +2330,9 @@ and type_expect_ ?in_function ?(recarg=Rejected) env sexp ty_expected =
                       Overridden ({loc ; txt = Lident lbl.lbl_name}, option_none lbl.lbl_arg loc))
                   label_descriptions
         in
-        if !labels_missing <> [] then
-          raise(Error(loc, env, Labels_missing (List.rev !labels_missing)));
+        if !labels_missing <> [] then (
+          let might_be_component = check_might_be_component env ty_record in
+          raise(Error(loc, env, Labels_missing ((List.rev !labels_missing), might_be_component))));
         let fields =
           Array.map2 (fun descr def -> descr, def)
             label_descriptions label_definitions
@@ -3862,11 +3869,12 @@ let report_error env ppf = function
         type_expr ty print_label l
   | Label_multiply_defined s ->
       fprintf ppf "The record field label %s is defined several times" s
-  | Labels_missing labels ->
+  | Labels_missing (labels, might_be_component) ->
       let print_labels ppf =
         List.iter (fun lbl -> fprintf ppf "@ %s" ( lbl)) in
-      fprintf ppf "@[<hov>Some required record fields are missing:%a. If this is a component, add the missing props.@]"
-        print_labels labels
+      let component_text = if might_be_component then " If this is a component, add the missing props." else "" in
+      fprintf ppf "@[<hov>Some required record fields are missing:%a.%s@]"
+        print_labels labels component_text
   | Label_not_mutable lid ->
       fprintf ppf "The record field %a is not mutable" longident lid
   | Wrong_name (eorp, ty, kind, p, name, valid_names) ->

jscomp/ml/typecore.mli

@@ -72,7 +72,7 @@ type error =
   | Apply_non_function of type_expr
   | Apply_wrong_label of arg_label * type_expr
   | Label_multiply_defined of string
-  | Labels_missing of string list
+  | Labels_missing of string list * bool
   | Label_not_mutable of Longident.t
   | Wrong_name of string * type_expr * string * Path.t * string * string list
   | Name_type_mismatch of