internal/goexperiment: delete RangeFunc goexperiment

It is now always enabeld. The GOEXPERIMENT doesn't control
anything. Remove.

Change-Id: I50eb09f4537f90ec28152eb59a5a689127843fce
Reviewed-on: https://go-review.googlesource.com/c/go/+/684838
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: cherrymui

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

@@ -399,12 +399,6 @@ func TestIssue47243_TypedRHS(t *testing.T) {
 }
 
 func TestCheck(t *testing.T) {
-	old := buildcfg.Experiment.RangeFunc
-	defer func() {
-		buildcfg.Experiment.RangeFunc = old
-	}()
-	buildcfg.Experiment.RangeFunc = true
-
 	DefPredeclaredTestFuncs()
 	testDirFiles(t, "../../../../internal/types/testdata/check", 50, false) // TODO(gri) narrow column tolerance
 }

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

@@ -9,7 +9,6 @@ package types2
 import (
 	"cmd/compile/internal/syntax"
 	"go/constant"
-	"internal/buildcfg"
 	. "internal/types/errors"
 )
 
@@ -237,7 +236,7 @@ func rangeKeyVal(check *Checker, orig Type, allowVersion func(goVersion) bool) (
 		assert(typ.dir != SendOnly)
 		return typ.elem, nil, "", true
 	case *Signature:
-		if !buildcfg.Experiment.RangeFunc && allowVersion != nil && !allowVersion(go1_23) {
+		if allowVersion != nil && !allowVersion(go1_23) {
 			return bad("requires go1.23 or later")
 		}
 		// check iterator arity

src/go/types/check_test.go

@@ -426,12 +426,6 @@ func TestIssue47243_TypedRHS(t *testing.T) {
 }
 
 func TestCheck(t *testing.T) {
-	old := buildcfg.Experiment.RangeFunc
-	defer func() {
-		buildcfg.Experiment.RangeFunc = old
-	}()
-	buildcfg.Experiment.RangeFunc = true
-
 	DefPredeclaredTestFuncs()
 	testDirFiles(t, "../../internal/types/testdata/check", false)
 }

src/go/types/range.go

@@ -100,9 +100,6 @@ type Flags struct {
 	// inlining phase within the Go compiler.
 	NewInliner bool
 
-	// RangeFunc enables range over func.
-	RangeFunc bool
-
 	// AliasTypeParams enables type parameters for alias types.
 	// Requires that gotypesalias=1 is set with GODEBUG.
 	// This flag will be removed with Go 1.25.

src/internal/goexperiment/exp_rangefunc_off.go

@@ -610,7 +610,6 @@ func testTraceProg(t *testing.T, progName string, extra func(t *testing.T, trace
 			buildCmd.Args = append(buildCmd.Args, "-race")
 		}
 		buildCmd.Args = append(buildCmd.Args, testPath)
-		buildCmd.Env = append(os.Environ(), "GOEXPERIMENT=rangefunc")
 		buildOutput, err := buildCmd.CombinedOutput()
 		if err != nil {
 			t.Fatalf("failed to build %s: %v: output:\n%s", testPath, err, buildOutput)

src/internal/goexperiment/exp_rangefunc_on.go

@@ -186,21 +186,6 @@ func buildTestProg(t *testing.T, binary string, flags ...string) (string, error)
 		t.Logf("running %v", cmd)
 		cmd.Dir = "testdata/" + binary
 		cmd = testenv.CleanCmdEnv(cmd)
-
-		// Add the rangefunc GOEXPERIMENT unconditionally since some tests depend on it.
-		// TODO(61405): Remove this once it's enabled by default.
-		edited := false
-		for i := range cmd.Env {
-			e := cmd.Env[i]
-			if _, vars, ok := strings.Cut(e, "GOEXPERIMENT="); ok {
-				cmd.Env[i] = "GOEXPERIMENT=" + vars + ",rangefunc"
-				edited = true
-			}
-		}
-		if !edited {
-			cmd.Env = append(cmd.Env, "GOEXPERIMENT=rangefunc")
-		}
-
 		out, err := cmd.CombinedOutput()
 		if err != nil {
 			target.err = fmt.Errorf("building %s %v: %v\n%s", binary, flags, err, out)

src/internal/goexperiment/flags.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build goexperiment.rangefunc
-
 package race_test
 
 import (