anchor.diff:        if (identical('native', token.stringValue) && parser != null) {
           Token nativeKeyword = token;
           Token semicolon = parser.parseLiteralString(token.next);
  +        // TODO(brianwilkerson) Should this be using ensureSemicolon?
           token = parser.expectSemicolon(semicolon);
           StringLiteral name = pop();
           pop(); // star
  
positive.code:             covariantKeyword: covariantKeyword,
              type: typeOrFunctionTypedParameter.returnType,
              thisKeyword: thisKeyword,
              period: thisKeyword.next,
              typeParameters: typeOrFunctionTypedParameter.typeParameters,
              parameters: typeOrFunctionTypedParameter.parameters);
        }
  
negative.code:         condition,
          rightSeparator,
          updates,
          leftParenthesis?.endGroup,
          body));
    }
  
  