fix go1.18

go.mod

@@ -1,3 +1,3 @@
 module github.com/modern-go/reflect2
 
-go 1.18
+go 1.12

go_above_118.go

@@ -0,0 +1,23 @@
+//+build go1.18
+
+package reflect2
+
+import (
+	"unsafe"
+)
+
+// m escapes into the return value, but the caller of mapiterinit
+// doesn't let the return value escape.
+//go:noescape
+//go:linkname mapiterinit reflect.mapiterinit
+func mapiterinit(rtype unsafe.Pointer, m unsafe.Pointer, it *hiter)
+
+func (type2 *UnsafeMapType) UnsafeIterate(obj unsafe.Pointer) MapIterator {
+	var it hiter
+	mapiterinit(type2.rtype, *(*unsafe.Pointer)(obj), &it)
+	return &UnsafeMapIterator{
+		hiter:      &it,
+		pKeyRType:  type2.pKeyRType,
+		pElemRType: type2.pElemRType,
+	}
+}

go_below_118.go

@@ -0,0 +1,21 @@
+//+build !go1.18
+
+package reflect2
+
+import (
+	"unsafe"
+)
+
+// m escapes into the return value, but the caller of mapiterinit
+// doesn't let the return value escape.
+//go:noescape
+//go:linkname mapiterinit reflect.mapiterinit
+func mapiterinit(rtype unsafe.Pointer, m unsafe.Pointer) (val *hiter)
+
+func (type2 *UnsafeMapType) UnsafeIterate(obj unsafe.Pointer) MapIterator {
+	return &UnsafeMapIterator{
+		hiter:      mapiterinit(type2.rtype, *(*unsafe.Pointer)(obj)),
+		pKeyRType:  type2.pKeyRType,
+		pElemRType: type2.pElemRType,
+	}
+}

unsafe_link.go

@@ -25,12 +25,6 @@ func mapassign(rtype unsafe.Pointer, m unsafe.Pointer, key unsafe.Pointer, val u
 //go:noescape
 func mapaccess(rtype unsafe.Pointer, m unsafe.Pointer, key unsafe.Pointer) (val unsafe.Pointer)
 
-// m escapes into the return value, but the caller of mapiterinit
-// doesn't let the return value escape.
-//go:noescape
-//go:linkname mapiterinit reflect.mapiterinit
-func mapiterinit(rtype unsafe.Pointer, m unsafe.Pointer, it *hiter)
-
 //go:noescape
 //go:linkname mapiternext reflect.mapiternext
 func mapiternext(it *hiter)

unsafe_map.go

@@ -107,16 +107,6 @@ func (type2 *UnsafeMapType) Iterate(obj interface{}) MapIterator {
 	return type2.UnsafeIterate(objEFace.data)
 }
 
-func (type2 *UnsafeMapType) UnsafeIterate(obj unsafe.Pointer) MapIterator {
-	var it hiter
-	mapiterinit(type2.rtype, *(*unsafe.Pointer)(obj), &it)
-	return &UnsafeMapIterator{
-		hiter:      &it,
-		pKeyRType:  type2.pKeyRType,
-		pElemRType: type2.pElemRType,
-	}
-}
-
 type UnsafeMapIterator struct {
 	*hiter
 	pKeyRType  unsafe.Pointer