all: enable range-over-func in Go 1.23

GOEXPERIMENT=rangefunc still enables it for all Go modules.
Otherwise only enable in Go 1.23 source files.
More work remains but it will be done in follow-up issues.

Fixes #61405.

Change-Id: Icad64942deb152ee65444e4d7be289814a8a0b6b
Reviewed-on: https://go-review.googlesource.com/c/go/+/557835
Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>

src/cmd/compile/internal/types2/stmt.go

@@ -1026,9 +1026,8 @@ func rangeKeyVal(typ Type, allowVersion func(goVersion) bool) (key, val Type, ca
 		}
 		return typ.elem, nil, "", false, true
 	case *Signature:
-		// TODO(gri) when this becomes enabled permanently, add version check
-		if !buildcfg.Experiment.RangeFunc {
-			break
+		if !buildcfg.Experiment.RangeFunc && allowVersion != nil && !allowVersion(go1_23) {
+			return bad("requires go1.23 or later")
 		}
 		assert(typ.Recv() == nil)
 		switch {

src/cmd/compile/internal/types2/version.go

@@ -44,6 +44,7 @@ var (
 	go1_20 = asGoVersion("go1.20")
 	go1_21 = asGoVersion("go1.21")
 	go1_22 = asGoVersion("go1.22")
+	go1_23 = asGoVersion("go1.23")
 
 	// current (deployed) Go version
 	go_current = asGoVersion(fmt.Sprintf("go1.%d", goversion.Version))

src/go/types/stmt.go

@@ -1010,9 +1010,8 @@ func rangeKeyVal(typ Type, allowVersion func(goVersion) bool) (key, val Type, ca
 		}
 		return typ.elem, nil, "", false, true
 	case *Signature:
-		// TODO(gri) when this becomes enabled permanently, add version check
-		if !buildcfg.Experiment.RangeFunc {
-			break
+		if !buildcfg.Experiment.RangeFunc && allowVersion != nil && !allowVersion(go1_23) {
+			return bad("requires go1.23 or later")
 		}
 		assert(typ.Recv() == nil)
 		switch {

src/go/types/version.go

@@ -45,6 +45,7 @@ var (
 	go1_20 = asGoVersion("go1.20")
 	go1_21 = asGoVersion("go1.21")
 	go1_22 = asGoVersion("go1.22")
+	go1_23 = asGoVersion("go1.23")
 
 	// current (deployed) Go version
 	go_current = asGoVersion(fmt.Sprintf("go1.%d", goversion.Version))

src/internal/types/testdata/spec/range.go

@@ -1,5 +1,3 @@
-// -goexperiment=rangefunc
-
 // Copyright 2023 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.