More improvements for generic subtpying error message.

ponylang · May 7, 2024 · 4d559f3 · 4d559f3
1 parent 52918cf
commit 4d559f3
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/src/libponyc/type/subtype.c b/src/libponyc/type/subtype.c
@@ -219,6 +219,9 @@ static bool is_eq_typeargs(ast_t* a, ast_t* b, errorframe_t* errorf,
     ast_error_frame(errorf, a,
       "%s has different type arguments than %s (the type arguments must be equivalent, not covariant nor contravariant)",
       ast_print_type(a), ast_print_type(b));
+    ast_error_frame(errorf, a,
+      "this might be possible if either %s or %s were an interface rather than a concrete type",
+      ast_print_type(a), ast_print_type(b));
   }
 
   // Make sure we had the same number of typeargs.