Use Parameter-Specific Diagnostic When Diagnosing Parameters

Author: CodaFi

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1019,13 +1019,11 @@ static void checkDefaultArguments(ParameterList *params) {
     // Placeholder types are banned for all parameter decls. We try to use the
     // freshly-checked default expression's contextual type to suggest a
     // reasonable type to insert.
+    param->diagnose(diag::placeholder_type_not_allowed_in_parameter)
+        .highlight(param->getSourceRange());
     if (expr && !expr->getType()->hasError()) {
-      param->diagnose(diag::placeholder_type_not_allowed_in_parameter)
-          .highlight(param->getSourceRange());
       TypeChecker::notePlaceholderReplacementTypes(
           ifacety, expr->getType()->mapTypeOutOfContext());
-    } else {
-      param->diagnose(diag::placeholder_type_not_allowed);
     }
   }
 }

test/Sema/placeholder_type.swift

@@ -249,7 +249,7 @@ func opaque() -> some _ { // expected-error {{type placeholder not allowed here}
 }
 
 enum EnumWithPlaceholders {
-  case topLevelPlaceholder(x: _) // expected-error {{type placeholder not allowed here}}
+  case topLevelPlaceholder(x: _) // expected-error {{type placeholder may not appear in top-level parameter}}
   case placeholderWithDefault(x: _ = 5) // expected-error {{type placeholder may not appear in top-level parameter}}
   // expected-note@-1 {{replace the placeholder with the correct type 'Int'}}
 }