github.com/goplus/llgo/internal/typeutil.Map

internal/aliases/aliases_go122.go

@@ -0,0 +1,63 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.22
+// +build go1.22
+
+package aliases
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"go/types"
+)
+
+// Alias is an alias of types.Alias.
+type Alias = types.Alias
+
+// Rhs returns the type on the right-hand side of the alias declaration.
+func Rhs(alias *Alias) types.Type {
+	if alias, ok := any(alias).(interface{ Rhs() types.Type }); ok {
+		return alias.Rhs() // go1.23+
+	}
+
+	// go1.22's Alias didn't have the Rhs method,
+	// so Unalias is the best we can do.
+	return Unalias(alias)
+}
+
+// Unalias is a wrapper of types.Unalias.
+func Unalias(t types.Type) types.Type { return types.Unalias(t) }
+
+// newAlias is an internal alias around types.NewAlias.
+// Direct usage is discouraged as the moment.
+// Try to use NewAlias instead.
+func newAlias(tname *types.TypeName, rhs types.Type) *Alias {
+	a := types.NewAlias(tname, rhs)
+	// TODO(go.dev/issue/65455): Remove kludgy workaround to set a.actual as a side-effect.
+	Unalias(a)
+	return a
+}
+
+// Enabled reports whether [NewAlias] should create [types.Alias] types.
+//
+// This function is expensive! Call it sparingly.
+func Enabled() bool {
+	// The only reliable way to compute the answer is to invoke go/types.
+	// We don't parse the GODEBUG environment variable, because
+	// (a) it's tricky to do so in a manner that is consistent
+	//     with the godebug package; in particular, a simple
+	//     substring check is not good enough. The value is a
+	//     rightmost-wins list of options. But more importantly:
+	// (b) it is impossible to detect changes to the effective
+	//     setting caused by os.Setenv("GODEBUG"), as happens in
+	//     many tests. Therefore any attempt to cache the result
+	//     is just incorrect.
+	fset := token.NewFileSet()
+	f, _ := parser.ParseFile(fset, "a.go", "package p; type A = int", 0)
+	pkg, _ := new(types.Config).Check("p", fset, []*ast.File{f}, nil)
+	_, enabled := pkg.Scope().Lookup("A").Type().(*types.Alias)
+	return enabled
+}