anchor.diff:    }
   
     ast.Initializer buildInitializer(ConstructorInitializer node) {
  -    return new InitializerBuilder(this).build(node);
  +    try {
  +      return new InitializerBuilder(this).build(node);
  +    } on _CompilationError catch (_) {
  +      return new ast.InvalidInitializer();
  +    }
     }
   
     bool isFinal(Element element) {
  
positive.code:     for (var parameter in formals) {
        var declaration = makeVariableDeclaration(parameter.element,
            initializer: parameter is DefaultFormalParameter
                ? buildOptionalExpression(parameter.defaultValue)
                : null,
            type: buildType(parameter.element.type));
        switch (parameter.kind) {
  
negative.code:             isAsync: body.isAsynchronous, isStar: body.isGenerator));
    }
  
    ast.Expression buildOptionalTopLevelExpression(Expression node) {
      return node == null ? null : buildTopLevelExpression(node);
    }
  
    ast.Expression buildTopLevelExpression(Expression node) {
      try {
        return _expressionBuilder.build(node);
  