Use shared error for constructor's with return type.

pkg/compiler/lib/src/diagnostics/generated/shared_messages.dart

Index: pkg/compiler/lib/src/diagnostics/generated/shared_messages.dart
diff --git a/pkg/compiler/lib/src/diagnostics/generated/shared_messages.dart b/pkg/compiler/lib/src/diagnostics/generated/shared_messages.dart
index e7ad53a4d070dc500a3cdd6e61267e8b111da00f..e39c8db85f77f4eb9604c09eb4d0d955bd10921e 100644
--- a/pkg/compiler/lib/src/diagnostics/generated/shared_messages.dart
+++ b/pkg/compiler/lib/src/diagnostics/generated/shared_messages.dart
@@ -65,4 +65,12 @@ const Map<MessageKind, MessageTemplate> TEMPLATES = const <MessageKind, MessageT
       "external foo; main(){}",
     ]
   ),  // Generated. Don't edit.
+  MessageKind.CONSTRUCTOR_WITH_RETURN_TYPE: const MessageTemplate(
+    MessageKind.CONSTRUCTOR_WITH_RETURN_TYPE,
+    "Constructors can't have a return type",
+    howToFix: "Try removing the return type.",
+    examples: const [
+      "class A { int A() {} } main() { new A(); }",
+    ]
+  ),  // Generated. Don't edit.
 };