internal/typesinternal: implement VarKind compatibility shim

For golang/go#70250

Change-Id: Ib7700c2516cf84f17d351e5580de752a9ec44c5b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/710616
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Madeline Kalil <mkalil@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>

Author: adonovan

internal/typesinternal/varkind.go

@@ -2,39 +2,22 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package typesinternal
+//go:build go1.25
 
-// TODO(adonovan): when CL 645115 lands, define the go1.25 version of
-// this API that actually does something.
+package typesinternal
 
 import "go/types"
 
-type VarKind uint8
+type VarKind = types.VarKind
 
 const (
-	_          VarKind = iota // (not meaningful)
-	PackageVar                // a package-level variable
-	LocalVar                  // a local variable
-	RecvVar                   // a method receiver variable
-	ParamVar                  // a function parameter variable
-	ResultVar                 // a function result variable
-	FieldVar                  // a struct field
+	PackageVar = types.PackageVar
+	LocalVar   = types.LocalVar
+	RecvVar    = types.RecvVar
+	ParamVar   = types.ParamVar
+	ResultVar  = types.ResultVar
+	FieldVar   = types.FieldVar
 )
 
-func (kind VarKind) String() string {
-	return [...]string{
-		0:          "VarKind(0)",
-		PackageVar: "PackageVar",
-		LocalVar:   "LocalVar",
-		RecvVar:    "RecvVar",
-		ParamVar:   "ParamVar",
-		ResultVar:  "ResultVar",
-		FieldVar:   "FieldVar",
-	}[kind]
-}
-
-// GetVarKind returns an invalid VarKind.
-func GetVarKind(v *types.Var) VarKind { return 0 }
-
-// SetVarKind has no effect.
-func SetVarKind(v *types.Var, kind VarKind) {}
+func GetVarKind(v *types.Var) VarKind       { return v.Kind() }
+func SetVarKind(v *types.Var, kind VarKind) { v.SetKind(kind) }

internal/typesinternal/varkind_go124.go

@@ -0,0 +1,39 @@
+// 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 !go1.25
+
+package typesinternal
+
+import "go/types"
+
+type VarKind uint8
+
+const (
+	_          VarKind = iota // (not meaningful)
+	PackageVar                // a package-level variable
+	LocalVar                  // a local variable
+	RecvVar                   // a method receiver variable
+	ParamVar                  // a function parameter variable
+	ResultVar                 // a function result variable
+	FieldVar                  // a struct field
+)
+
+func (kind VarKind) String() string {
+	return [...]string{
+		0:          "VarKind(0)",
+		PackageVar: "PackageVar",
+		LocalVar:   "LocalVar",
+		RecvVar:    "RecvVar",
+		ParamVar:   "ParamVar",
+		ResultVar:  "ResultVar",
+		FieldVar:   "FieldVar",
+	}[kind]
+}
+
+// GetVarKind returns an invalid VarKind.
+func GetVarKind(v *types.Var) VarKind { return 0 }
+
+// SetVarKind has no effect.
+func SetVarKind(v *types.Var, kind VarKind) {}