Update metadata syntax test to check for non-existing constants and type literals (see issue 14647).

tests/language/metadata_syntax_test.dart

Index: tests/language/metadata_syntax_test.dart
diff --git a/tests/language/metadata_syntax_test.dart b/tests/language/metadata_syntax_test.dart
index dc3ff8cccb5b76a09be7d7d8968c67472d35cc32..8c3fe13703f3af77e11099684eeedbc1cd16ee61 100644
--- a/tests/language/metadata_syntax_test.dart
+++ b/tests/language/metadata_syntax_test.dart
@@ -16,10 +16,27 @@ class Bar {
 
   @Bar()
   @List<String> /// 03: compile-time error
-  final x = '';
+  final x = 'x';
+
+  @unknown /// 04: compile-time error
+  final y = 'y';
+
+  @Bar /// 05: compile-time error
+  final z = 'z';
+
+  @1234 /// 06: compile-time error
+  final w = 'w';
 }
 
 main() {
-  Expect.equals('', new Bar().x);
-  Expect.equals('', const Bar().x);
+  Expect.equals('x', new Bar().x);
+  Expect.equals('x', const Bar().x);
+  Expect.equals('y', new Bar().y);
+  Expect.equals('y', const Bar().y);
+  Expect.equals('z', new Bar().z);
+  Expect.equals('z', const Bar().z);
+  Expect.equals('z', new Bar().z);
+  Expect.equals('z', const Bar().z);
+  Expect.equals('w', new Bar().w);
+  Expect.equals('w', const Bar().w);
 }