72 lines
1.6 KiB
Go
72 lines
1.6 KiB
Go
// Copyright 2023 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package astutil
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import (
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"go/ast"
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"reflect"
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)
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// CloneNode returns a deep copy of a Node.
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// It omits pointers to ast.{Scope,Object} variables.
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func CloneNode[T ast.Node](n T) T {
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return cloneNode(n).(T)
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}
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func cloneNode(n ast.Node) ast.Node {
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var clone func(x reflect.Value) reflect.Value
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set := func(dst, src reflect.Value) {
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src = clone(src)
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if src.IsValid() {
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dst.Set(src)
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}
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}
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clone = func(x reflect.Value) reflect.Value {
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switch x.Kind() {
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case reflect.Pointer:
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if x.IsNil() {
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return x
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}
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// Skip fields of types potentially involved in cycles.
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switch x.Interface().(type) {
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case *ast.Object, *ast.Scope:
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return reflect.Zero(x.Type())
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}
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y := reflect.New(x.Type().Elem())
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set(y.Elem(), x.Elem())
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return y
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case reflect.Struct:
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y := reflect.New(x.Type()).Elem()
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for i := 0; i < x.Type().NumField(); i++ {
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set(y.Field(i), x.Field(i))
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}
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return y
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case reflect.Slice:
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if x.IsNil() {
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return x
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}
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y := reflect.MakeSlice(x.Type(), x.Len(), x.Cap())
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for i := 0; i < x.Len(); i++ {
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set(y.Index(i), x.Index(i))
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}
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return y
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case reflect.Interface:
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y := reflect.New(x.Type()).Elem()
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set(y, x.Elem())
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return y
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case reflect.Array, reflect.Chan, reflect.Func, reflect.Map, reflect.UnsafePointer:
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panic(x) // unreachable in AST
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default:
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return x // bool, string, number
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}
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}
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return clone(reflect.ValueOf(n)).Interface().(ast.Node)
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}
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