anchor.diff:        return parseFunctionDeclaration(
             commentAndMetadata, modifiers.externalKeyword, null);
       } else if (_tokenMatches(next, TokenType.OPEN_PAREN)) {
  -      TypeName returnType = _parseOptionalTypeNameComment();
  +      TypeName returnType = null;
         _validateModifiersForTopLevelFunction(modifiers);
         return parseFunctionDeclaration(
             commentAndMetadata, modifiers.externalKeyword, returnType);
  
positive.code:    * advancing. Return the return type that was parsed.
     */
    TypeAnnotation _parseOptionalReturnType() {
      TypeName typeComment = _parseOptionalTypeNameComment();
      if (typeComment != null) {
        return typeComment;
      }
      Keyword keyword = _currentToken.keyword;
      if (keyword == Keyword.VOID) {
        if (_atGenericFunctionTypeAfterReturnType(_peek())) {
  
negative.code:     }
      _reportError(new AnalysisError(_source, token.offset,
          math.max(token.length, 1), errorCode, arguments));
    }
  
    /**
  