我在 Roslyn 中使用 SyntaxRewriter 时遇到了一个棘手的情况。我想重写某些类型的语句,包括局部变量声明。该解决方案要求我将有问题的语句转换为多个语句,如以下简单示例所示:
void method()
{
int i;
}
变成了
void method()
{
int i;
Console.WriteLine("I declared a variable.");
}
我见过其他例子,其中使用 block 来完成类似的事情,但是当然在变量声明的情况下,声明的范围会受到影响。我想出了以下解决方案,但我对此犹豫不决。它看起来过于复杂,需要打破访问者模式:
class Rewriter: SyntaxRewriter
{
public override SyntaxList<TNode> VisitList<TNode>(SyntaxList<TNode> list)
{
if (typeof(TNode) == typeof(StatementSyntax))
return Syntax.List<TNode>(list.SelectMany(st => RewriteStatementInList(st as StatementSyntax).Cast<TNode>()));
else
return base.VisitList<TNode>(list);
}
private IEnumerable<SyntaxNode> RewriteStatementInList(StatementSyntax node)
{
if (node is LocalDeclarationStatementSyntax)
return PerformRewrite((LocalDeclarationStatementSyntax)node);
//else if other cases (non-visitor)
return Visit(node).AsSingleEnumerableOf();
}
private IEnumerable<SyntaxNode> PerformRewrite(LocalDeclarationStatementSyntax orig)
{
yield return orig;
yield return Syntax.ParseStatement("Console.WriteLine(\"I declared a variable.\");");
}
}
我错过了什么?编辑语句并删除它们(通过空语句)似乎比重写为倍数更直接。
我对答案的看法:
class Rewriter : SyntaxRewriter
{
readonly ListVisitor _visitor = new ListVisitor();
public override SyntaxList<TNode> VisitList<TNode>(SyntaxList<TNode> list)
{
var result = Syntax.List(list.SelectMany(_visitor.Visit).Cast<TNode>());
return base.VisitList(result);
}
private class ListVisitor : SyntaxVisitor<IEnumerable<SyntaxNode>>
{
protected override IEnumerable<SyntaxNode> DefaultVisit(SyntaxNode node)
{
yield return node;
}
protected override IEnumerable<SyntaxNode> VisitLocalDeclarationStatement(
LocalDeclarationStatementSyntax node)
{
yield return node;
yield return Syntax.ParseStatement("Console.WriteLine(\"I declared a variable.\");");
}
}
}
最佳答案
我认为有一种简单的方法可以使您的Rewriter
更像访问者:使用另一个访问者来处理列表中的节点:
class Rewriter: SyntaxRewriter
{
readonly Visitor m_visitor = new Visitor();
public override SyntaxList<TNode> VisitList<TNode>(SyntaxList<TNode> list)
{
var result = Syntax.List(list.SelectMany(m_visitor.Visit).Cast<TNode>());
return base.VisitList(result);
}
}
class Visitor : SyntaxVisitor<IEnumerable<SyntaxNode>>
{
protected override IEnumerable<SyntaxNode> DefaultVisit(SyntaxNode node)
{
return new[] { node };
}
protected override IEnumerable<SyntaxNode> VisitLocalDeclarationStatement(
LocalDeclarationStatementSyntax node)
{
return new SyntaxNode[]
{
node,
Syntax.ParseStatement(
"Console.WriteLine(\"I declared a variable.\");")
};
}
}
请注意,这并不安全,如果您从 Visitor
返回的集合包含非 TNode
的对象,则会抛出 InvalidCastException
.
关于roslyn - SyntaxRewriter 和多个语句,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/9775335/