mirror of
https://github.com/tailscale/tailscale.git
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fd0acc4faf
Updates #12736 Signed-off-by: Nick Khyl <nickk@tailscale.com>
269 lines
8.4 KiB
Go
269 lines
8.4 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Cloner is a tool to automate the creation of a Clone method.
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//
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// The result of the Clone method aliases no memory that can be edited
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// with the original.
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//
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// This tool makes lots of implicit assumptions about the types you feed it.
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// In particular, it can only write relatively "shallow" Clone methods.
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// That is, if a type contains another named struct type, cloner assumes that
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// named type will also have a Clone method.
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package main
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import (
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"bytes"
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"flag"
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"fmt"
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"go/types"
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"log"
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"os"
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"strings"
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"tailscale.com/util/codegen"
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)
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var (
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flagTypes = flag.String("type", "", "comma-separated list of types; required")
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flagBuildTags = flag.String("tags", "", "compiler build tags to apply")
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flagCloneFunc = flag.Bool("clonefunc", false, "add a top-level Clone func")
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)
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func main() {
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log.SetFlags(0)
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log.SetPrefix("cloner: ")
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flag.Parse()
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if len(*flagTypes) == 0 {
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flag.Usage()
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os.Exit(2)
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}
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typeNames := strings.Split(*flagTypes, ",")
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pkg, namedTypes, err := codegen.LoadTypes(*flagBuildTags, ".")
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if err != nil {
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log.Fatal(err)
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}
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it := codegen.NewImportTracker(pkg.Types)
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buf := new(bytes.Buffer)
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for _, typeName := range typeNames {
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typ, ok := namedTypes[typeName]
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if !ok {
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log.Fatalf("could not find type %s", typeName)
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}
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gen(buf, it, typ)
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}
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w := func(format string, args ...any) {
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fmt.Fprintf(buf, format+"\n", args...)
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}
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if *flagCloneFunc {
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w("// Clone duplicates src into dst and reports whether it succeeded.")
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w("// To succeed, <src, dst> must be of types <*T, *T> or <*T, **T>,")
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w("// where T is one of %s.", *flagTypes)
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w("func Clone(dst, src any) bool {")
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w(" switch src := src.(type) {")
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for _, typeName := range typeNames {
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w(" case *%s:", typeName)
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w(" switch dst := dst.(type) {")
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w(" case *%s:", typeName)
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w(" *dst = *src.Clone()")
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w(" return true")
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w(" case **%s:", typeName)
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w(" *dst = src.Clone()")
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w(" return true")
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w(" }")
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}
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w(" }")
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w(" return false")
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w("}")
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}
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cloneOutput := pkg.Name + "_clone"
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if *flagBuildTags == "test" {
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cloneOutput += "_test"
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}
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cloneOutput += ".go"
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if err := codegen.WritePackageFile("tailscale.com/cmd/cloner", pkg, cloneOutput, it, buf); err != nil {
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log.Fatal(err)
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}
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}
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func gen(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named) {
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t, ok := typ.Underlying().(*types.Struct)
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if !ok {
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return
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}
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name := typ.Obj().Name()
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typeParams := typ.Origin().TypeParams()
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_, typeParamNames := codegen.FormatTypeParams(typeParams, it)
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nameWithParams := name + typeParamNames
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fmt.Fprintf(buf, "// Clone makes a deep copy of %s.\n", name)
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fmt.Fprintf(buf, "// The result aliases no memory with the original.\n")
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fmt.Fprintf(buf, "func (src *%s) Clone() *%s {\n", nameWithParams, nameWithParams)
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writef := func(format string, args ...any) {
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fmt.Fprintf(buf, "\t"+format+"\n", args...)
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}
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writef("if src == nil {")
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writef("\treturn nil")
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writef("}")
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writef("dst := new(%s)", nameWithParams)
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writef("*dst = *src")
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for i := range t.NumFields() {
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fname := t.Field(i).Name()
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ft := t.Field(i).Type()
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if !codegen.ContainsPointers(ft) || codegen.HasNoClone(t.Tag(i)) {
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continue
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}
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if named, _ := ft.(*types.Named); named != nil {
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if codegen.IsViewType(ft) {
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writef("dst.%s = src.%s", fname, fname)
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continue
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}
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if !hasBasicUnderlying(ft) {
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writef("dst.%s = *src.%s.Clone()", fname, fname)
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continue
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}
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}
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switch ft := ft.Underlying().(type) {
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case *types.Slice:
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if codegen.ContainsPointers(ft.Elem()) {
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n := it.QualifiedName(ft.Elem())
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writef("if src.%s != nil {", fname)
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writef("dst.%s = make([]%s, len(src.%s))", fname, n, fname)
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writef("for i := range dst.%s {", fname)
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if ptr, isPtr := ft.Elem().(*types.Pointer); isPtr {
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writef("if src.%s[i] == nil { dst.%s[i] = nil } else {", fname, fname)
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if codegen.ContainsPointers(ptr.Elem()) {
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if _, isIface := ptr.Elem().Underlying().(*types.Interface); isIface {
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it.Import("tailscale.com/types/ptr")
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writef("\tdst.%s[i] = ptr.To((*src.%s[i]).Clone())", fname, fname)
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} else {
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writef("\tdst.%s[i] = src.%s[i].Clone()", fname, fname)
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}
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} else {
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it.Import("tailscale.com/types/ptr")
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writef("\tdst.%s[i] = ptr.To(*src.%s[i])", fname, fname)
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}
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writef("}")
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} else if ft.Elem().String() == "encoding/json.RawMessage" {
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writef("\tdst.%s[i] = append(src.%s[i][:0:0], src.%s[i]...)", fname, fname, fname)
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} else if _, isIface := ft.Elem().Underlying().(*types.Interface); isIface {
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writef("\tdst.%s[i] = src.%s[i].Clone()", fname, fname)
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} else {
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writef("\tdst.%s[i] = *src.%s[i].Clone()", fname, fname)
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}
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writef("}")
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writef("}")
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} else {
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writef("dst.%s = append(src.%s[:0:0], src.%s...)", fname, fname, fname)
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}
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case *types.Pointer:
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base := ft.Elem()
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hasPtrs := codegen.ContainsPointers(base)
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if named, _ := base.(*types.Named); named != nil && hasPtrs {
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writef("dst.%s = src.%s.Clone()", fname, fname)
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continue
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}
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it.Import("tailscale.com/types/ptr")
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writef("if dst.%s != nil {", fname)
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if _, isIface := base.Underlying().(*types.Interface); isIface && hasPtrs {
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writef("\tdst.%s = ptr.To((*src.%s).Clone())", fname, fname)
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} else if !hasPtrs {
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writef("\tdst.%s = ptr.To(*src.%s)", fname, fname)
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} else {
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writef("\t" + `panic("TODO pointers in pointers")`)
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}
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writef("}")
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case *types.Map:
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elem := ft.Elem()
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if sliceType, isSlice := elem.(*types.Slice); isSlice {
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n := it.QualifiedName(sliceType.Elem())
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writef("if dst.%s != nil {", fname)
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writef("\tdst.%s = map[%s]%s{}", fname, it.QualifiedName(ft.Key()), it.QualifiedName(elem))
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writef("\tfor k := range src.%s {", fname)
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// use zero-length slice instead of nil to ensure
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// the key is always copied.
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writef("\t\tdst.%s[k] = append([]%s{}, src.%s[k]...)", fname, n, fname)
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writef("\t}")
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writef("}")
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} else if codegen.ContainsPointers(elem) {
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writef("if dst.%s != nil {", fname)
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writef("\tdst.%s = map[%s]%s{}", fname, it.QualifiedName(ft.Key()), it.QualifiedName(elem))
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writef("\tfor k, v := range src.%s {", fname)
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switch elem := elem.Underlying().(type) {
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case *types.Pointer:
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writef("\t\tif v == nil { dst.%s[k] = nil } else {", fname)
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if base := elem.Elem().Underlying(); codegen.ContainsPointers(base) {
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if _, isIface := base.(*types.Interface); isIface {
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it.Import("tailscale.com/types/ptr")
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writef("\t\t\tdst.%s[k] = ptr.To((*v).Clone())", fname)
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} else {
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writef("\t\t\tdst.%s[k] = v.Clone()", fname)
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}
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} else {
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it.Import("tailscale.com/types/ptr")
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writef("\t\t\tdst.%s[k] = ptr.To(*v)", fname)
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}
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writef("}")
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case *types.Interface:
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if cloneResultType := methodResultType(elem, "Clone"); cloneResultType != nil {
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if _, isPtr := cloneResultType.(*types.Pointer); isPtr {
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writef("\t\tdst.%s[k] = *(v.Clone())", fname)
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} else {
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writef("\t\tdst.%s[k] = v.Clone()", fname)
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}
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} else {
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writef(`panic("%s (%v) does not have a Clone method")`, fname, elem)
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}
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default:
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writef("\t\tdst.%s[k] = *(v.Clone())", fname)
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}
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writef("\t}")
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writef("}")
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} else {
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it.Import("maps")
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writef("\tdst.%s = maps.Clone(src.%s)", fname, fname)
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}
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case *types.Interface:
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// If ft is an interface with a "Clone() ft" method, it can be used to clone the field.
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// This includes scenarios where ft is a constrained type parameter.
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if cloneResultType := methodResultType(ft, "Clone"); cloneResultType.Underlying() == ft {
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writef("dst.%s = src.%s.Clone()", fname, fname)
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continue
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}
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writef(`panic("%s (%v) does not have a compatible Clone method")`, fname, ft)
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default:
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writef(`panic("TODO: %s (%T)")`, fname, ft)
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}
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}
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writef("return dst")
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fmt.Fprintf(buf, "}\n\n")
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buf.Write(codegen.AssertStructUnchanged(t, name, typeParams, "Clone", it))
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}
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// hasBasicUnderlying reports true when typ.Underlying() is a slice or a map.
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func hasBasicUnderlying(typ types.Type) bool {
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switch typ.Underlying().(type) {
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case *types.Slice, *types.Map:
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return true
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default:
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return false
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}
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}
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func methodResultType(typ types.Type, method string) types.Type {
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viewMethod := codegen.LookupMethod(typ, method)
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if viewMethod == nil {
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return nil
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}
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sig, ok := viewMethod.Type().(*types.Signature)
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if !ok || sig.Results().Len() != 1 {
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return nil
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}
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return sig.Results().At(0).Type()
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}
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