73 lines
1.7 KiB
Go
73 lines
1.7 KiB
Go
// Copyright 2024 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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//go:build go1.22
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// +build go1.22
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package aliases
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import (
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"go/ast"
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"go/parser"
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"go/token"
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"go/types"
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"os"
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"strings"
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"sync"
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)
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// Alias is an alias of types.Alias.
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type Alias = types.Alias
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// Unalias is a wrapper of types.Unalias.
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func Unalias(t types.Type) types.Type { return types.Unalias(t) }
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// newAlias is an internal alias around types.NewAlias.
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// Direct usage is discouraged as the moment.
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// Try to use NewAlias instead.
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func newAlias(tname *types.TypeName, rhs types.Type) *Alias {
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a := types.NewAlias(tname, rhs)
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// TODO(go.dev/issue/65455): Remove kludgy workaround to set a.actual as a side-effect.
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Unalias(a)
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return a
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}
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// enabled returns true when types.Aliases are enabled.
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func enabled() bool {
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// Use the gotypesalias value in GODEBUG if set.
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godebug := os.Getenv("GODEBUG")
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value := -1 // last set value.
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for _, f := range strings.Split(godebug, ",") {
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switch f {
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case "gotypesalias=1":
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value = 1
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case "gotypesalias=0":
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value = 0
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}
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}
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switch value {
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case 0:
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return false
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case 1:
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return true
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default:
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return aliasesDefault()
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}
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}
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// aliasesDefault reports if aliases are enabled by default.
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func aliasesDefault() bool {
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// Dynamically check if Aliases will be produced from go/types.
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aliasesDefaultOnce.Do(func() {
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fset := token.NewFileSet()
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f, _ := parser.ParseFile(fset, "a.go", "package p; type A = int", 0)
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pkg, _ := new(types.Config).Check("p", fset, []*ast.File{f}, nil)
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_, gotypesaliasDefault = pkg.Scope().Lookup("A").Type().(*types.Alias)
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})
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return gotypesaliasDefault
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}
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var gotypesaliasDefault bool
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var aliasesDefaultOnce sync.Once
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