try to improve error message about inline record escaping scope

Author: zth

compiler/ml/typecore.ml

@@ -4598,8 +4598,14 @@ let report_error env loc ppf error =
       "@[Exception patterns must be at the top level of a match case.@]"
   | Inlined_record_escape ->
     fprintf ppf
-      "@[This form is not allowed as the type of the inlined record could \
-       escape.@]"
+      "@[This use of an inlined record is not allowed: its anonymous type \
+       would escape its constructor scope.@,\
+       @,\
+       Possible solutions: @,\
+       - Destructure the fields you're interested in from the inline record@,\
+       - Change the underlying type to use a defined record as payload instead \
+       of an inline record. That will let you use the payload without \
+       destructuring it first"
   | Inlined_record_expected ->
     fprintf ppf "@[This constructor expects an inlined record argument.@]"
   | Invalid_extension_constructor_payload ->

tests/build_tests/super_errors/expected/inline_record_escape.res.expected

@@ -0,0 +1,14 @@
+
+  We've found a bug for you!
+  /.../fixtures/inline_record_escape.res:5:15
+
+  3 │ let g = (v: x) =>
+  4 │   switch v {
+  5 │   | One(r) => r
+  6 │   }
+  7 │ 
+
+  This use of an inlined record is not allowed: its anonymous type would escape its constructor scope.
+  Possible solutions: 
+  - Destructure the fields you're interested in from the inline record
+  - Change the underlying type to use a defined record as payload instead of an inline record. That will let you use the payload without destructuring it first

tests/build_tests/super_errors/fixtures/inline_record_escape.res

@@ -0,0 +1,6 @@
+type x = One({test: bool})
+
+let g = (v: x) =>
+  switch v {
+  | One(r) => r
+  }