anchor.diff:    Token leftParenthesis;
   
     /// The condition used to determine which of the branches is executed next.
  -  ExpressionImpl _condition;
  +  IfConditionImpl _condition;
   
     @override
     Token rightParenthesis;
  
positive.code:   bool get isAssignable => true;
  }
  
  class IfElementImpl extends CollectionElementImpl implements IfElement {
    @override
    Token ifKeyword;
  
negative.code: ///        ( 'final' | 'var' ) [DartPattern] '=' [Expression]
  @experimental
  class PatternVariableDeclarationImpl extends AstNodeImpl
      implements IfConditionImpl, PatternVariableDeclaration {
    @override
    final Token equals;
  
  