anchor.diff:  ///    typeParameterVariance ::= 'out' | 'inout' | 'in'
   class TypeParameterImpl extends DeclarationImpl implements TypeParameter {
     @override
  -  Token name;
  +  final Token name;
   
     /// The token representing the variance modifier keyword, or `null` if
     /// there is no explicit variance modifier, meaning legacy covariance.
  
positive.code: class ThisExpressionImpl extends ExpressionImpl implements ThisExpression {
    /// The token representing the 'this' keyword.
    @override
    Token thisKeyword;
  
    /// Initialize a newly created this expression.
    ThisExpressionImpl({
  
negative.code: class BlockImpl extends StatementImpl implements Block {
    /// The left curly bracket.
    @override
    final Token leftBracket;
  
    /// The statements contained in the block.
    final NodeListImpl<StatementImpl> _statements = NodeListImpl._();
  
    /// The right curly bracket.
    @override
    final Token rightBracket;
  
    /// Initialize a newly created block of code.
    BlockImpl({
  