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package ast
import "fmt"
// WalkFunc describes a function to be called for each node during a Walk. The
// returned node can be used to rewrite the AST. Walking stops the returned
// bool is false.
type WalkFunc func(Node) (Node, bool)
// Walk traverses an AST in depth-first order: It starts by calling fn(node);
// node must not be nil. If fn returns true, Walk invokes fn recursively for
// each of the non-nil children of node, followed by a call of fn(nil). The
// returned node of fn can be used to rewrite the passed node to fn.
func Walk(node Node, fn WalkFunc) Node {
rewritten, ok := fn(node)
if !ok {
return rewritten
}
switch n := node.(type) {
case *File:
n.Node = Walk(n.Node, fn)
case *ObjectList:
for i, item := range n.Items {
n.Items[i] = Walk(item, fn).(*ObjectItem)
}
case *ObjectKey:
// nothing to do
case *ObjectItem:
for i, k := range n.Keys {
n.Keys[i] = Walk(k, fn).(*ObjectKey)
}
if n.Val != nil {
n.Val = Walk(n.Val, fn)
}
case *LiteralType:
// nothing to do
case *ListType:
for i, l := range n.List {
n.List[i] = Walk(l, fn)
}
case *ObjectType:
n.List = Walk(n.List, fn).(*ObjectList)
default:
// should we panic here?
fmt.Printf("unknown type: %T\n", n)
}
fn(nil)
return rewritten
}
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