anchor.diff:      }
     }
   
  +  /// Parse any top-level declaration that begins with a keyword.
     Token parseTopLevelKeywordDeclaration(
         Token abstractToken, Token token, DirectiveContext directiveState) {
  +    assert(token.isTopLevelKeyword);
       final String value = token.stringValue;
       if (identical(value, 'class')) {
         directiveState?.checkDeclaration();
  
positive.code:     }
    }
  
    Token parseLabel(Token token) {
      token = parseIdentifier(token, IdentifierContext.labelDeclaration);
      Token colon = token;
      token = expect(':', token);
  
negative.code:     return token;
    }
  
    /// ```
    /// expressionStatement:
    ///   expression? ';'
    /// ;
    /// ```
    Token parseExpressionStatement(Token token) {
      // TODO(brianwilkerson): If the next token is not the start of a valid
      // expression, then this method shouldn't report that we have an expression
      // statement.
      listener.beginExpressionStatement(token);
  