go/types, types2: report error for range over int if Go version < 1.22

Fixes golang#64704.

Change-Id: Ied3af46ab534343cdafba5ee27680b9c6ef3d37a
Reviewed-on: https://go-review.googlesource.com/c/go/+/549459
Auto-Submit: Robert Griesemer <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Run-TryBot: Robert Griesemer <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

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

@@ -861,7 +861,9 @@ func (check *Checker) rangeStmt(inner stmtContext, s *syntax.ForStmt, rclause *s
 	var key, val Type
 	if x.mode != invalid {
 		// Ranging over a type parameter is permitted if it has a core type.
-		k, v, cause, isFunc, ok := rangeKeyVal(x.typ)
+		k, v, cause, isFunc, ok := rangeKeyVal(x.typ, func(v goVersion) bool {
+			return check.allowVersion(check.pkg, x.expr, v)
+		})
 		switch {
 		case !ok && cause != "":
 			check.softErrorf(&x, InvalidRangeExpr, "cannot range over %s: %s", &x, cause)
@@ -964,16 +966,18 @@ func (check *Checker) rangeStmt(inner stmtContext, s *syntax.ForStmt, rclause *s
 }
 
 // RangeKeyVal returns the key and value types for a range over typ.
+// Exported for use by the compiler (does not exist in go/types).
 func RangeKeyVal(typ Type) (Type, Type) {
-	key, val, _, _, _ := rangeKeyVal(typ)
+	key, val, _, _, _ := rangeKeyVal(typ, nil)
 	return key, val
 }
 
 // rangeKeyVal returns the key and value type produced by a range clause
-// over an expression of type typ. If the range clause is not permitted,
-// rangeKeyVal returns ok = false. When ok = false, rangeKeyVal may also
-// return a reason in cause.
-func rangeKeyVal(typ Type) (key, val Type, cause string, isFunc, ok bool) {
+// over an expression of type typ.
+// If allowVersion != nil, it is used to check the required language version.
+// If the range clause is not permitted, rangeKeyVal returns ok = false.
+// When ok = false, rangeKeyVal may also return a reason in cause.
+func rangeKeyVal(typ Type, allowVersion func(goVersion) bool) (key, val Type, cause string, isFunc, ok bool) {
 	bad := func(cause string) (Type, Type, string, bool, bool) {
 		return Typ[Invalid], Typ[Invalid], cause, false, false
 	}
@@ -991,6 +995,9 @@ func rangeKeyVal(typ Type) (key, val Type, cause string, isFunc, ok bool) {
 			return Typ[Int], universeRune, "", false, true // use 'rune' name
 		}
 		if isInteger(typ) {
+			if allowVersion != nil && !allowVersion(go1_22) {
+				return bad("requires go1.22 or later")
+			}
 			return orig, nil, "", false, true
 		}
 	case *Array:
@@ -1005,6 +1012,7 @@ func rangeKeyVal(typ Type) (key, val Type, cause string, isFunc, ok bool) {
 		}
 		return typ.elem, nil, "", false, true
 	case *Signature:
+		// TODO(gri) when this becomes enabled permanently, add version check
 		if !buildcfg.Experiment.RangeFunc {
 			break
 		}

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

@@ -43,6 +43,7 @@ var (
 	go1_18 = asGoVersion("go1.18")
 	go1_20 = asGoVersion("go1.20")
 	go1_21 = asGoVersion("go1.21")
+	go1_22 = asGoVersion("go1.22")
 
 	// current (deployed) Go version
 	go_current = asGoVersion(fmt.Sprintf("go1.%d", goversion.Version))

src/go/types/stmt.go

@@ -852,7 +852,9 @@ func (check *Checker) rangeStmt(inner stmtContext, s *ast.RangeStmt) {
 	var key, val Type
 	if x.mode != invalid {
 		// Ranging over a type parameter is permitted if it has a core type.
-		k, v, cause, isFunc, ok := rangeKeyVal(x.typ)
+		k, v, cause, isFunc, ok := rangeKeyVal(x.typ, func(v goVersion) bool {
+			return check.allowVersion(check.pkg, x.expr, v)
+		})
 		switch {
 		case !ok && cause != "":
 			check.softErrorf(&x, InvalidRangeExpr, "cannot range over %s: %s", &x, cause)
@@ -955,10 +957,11 @@ func (check *Checker) rangeStmt(inner stmtContext, s *ast.RangeStmt) {
 }
 
 // rangeKeyVal returns the key and value type produced by a range clause
-// over an expression of type typ. If the range clause is not permitted,
-// rangeKeyVal returns ok = false. When ok = false, rangeKeyVal may also
-// return a reason in cause.
-func rangeKeyVal(typ Type) (key, val Type, cause string, isFunc, ok bool) {
+// over an expression of type typ.
+// If allowVersion != nil, it is used to check the required language version.
+// If the range clause is not permitted, rangeKeyVal returns ok = false.
+// When ok = false, rangeKeyVal may also return a reason in cause.
+func rangeKeyVal(typ Type, allowVersion func(goVersion) bool) (key, val Type, cause string, isFunc, ok bool) {
 	bad := func(cause string) (Type, Type, string, bool, bool) {
 		return Typ[Invalid], Typ[Invalid], cause, false, false
 	}
@@ -976,6 +979,9 @@ func rangeKeyVal(typ Type) (key, val Type, cause string, isFunc, ok bool) {
 			return Typ[Int], universeRune, "", false, true // use 'rune' name
 		}
 		if isInteger(typ) {
+			if allowVersion != nil && !allowVersion(go1_22) {
+				return bad("requires go1.22 or later")
+			}
 			return orig, nil, "", false, true
 		}
 	case *Array:
@@ -990,6 +996,7 @@ func rangeKeyVal(typ Type) (key, val Type, cause string, isFunc, ok bool) {
 		}
 		return typ.elem, nil, "", false, true
 	case *Signature:
+		// TODO(gri) when this becomes enabled permanently, add version check
 		if !buildcfg.Experiment.RangeFunc {
 			break
 		}

src/go/types/version.go

@@ -44,6 +44,7 @@ var (
 	go1_18 = asGoVersion("go1.18")
 	go1_20 = asGoVersion("go1.20")
 	go1_21 = asGoVersion("go1.21")
+	go1_22 = asGoVersion("go1.22")
 
 	// current (deployed) Go version
 	go_current = asGoVersion(fmt.Sprintf("go1.%d", goversion.Version))

src/internal/types/testdata/fixedbugs/issue64704.go

@@ -0,0 +1,12 @@
+// -lang=go1.21
+
+// 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.
+
+package p
+
+func _() {
+	for range 10 /* ERROR "cannot range over 10 (untyped int constant): requires go1.22 or later" */ {
+	}
+}