Re-land "Add support for metadata on type variables to Fasta parser." (with fixes).

pkg/analyzer/test/generated/parser_test.dart

Index: pkg/analyzer/test/generated/parser_test.dart
diff --git a/pkg/analyzer/test/generated/parser_test.dart b/pkg/analyzer/test/generated/parser_test.dart
index 264cb69154d76ddd3b0d5672c2e5133bbd3c21f6..bda6d6bad66af639e3948e90044b00b7dc67374c 100644
--- a/pkg/analyzer/test/generated/parser_test.dart
+++ b/pkg/analyzer/test/generated/parser_test.dart
@@ -14729,6 +14729,17 @@ enum E {
     expectCommentText(typeAlias.documentationComment, '/// Doc');
   }
 
+  void test_parseTypeVariable_withDocumentationComment() {
+    createParser('''
+class A<
+    /// Doc
+    B> {}
+''');
+    var classDeclaration = parseFullCompilationUnitMember() as ClassDeclaration;
+    var typeVariable = classDeclaration.typeParameters.typeParameters[0];
+    expectCommentText(typeVariable.documentationComment, '/// Doc');
+  }
+
   /**
    * Assert that the given [name] is in declaration context.
    */