reflect, internal/reflectlite: add Value.SetIter{Key,Value} and MapIter.Reset

Fixes #4790. Depends on #4787 (merge that first).

src/internal/reflectlite/value.go

@@ -1102,20 +1102,9 @@ func hashmapNewIterator() unsafe.Pointer
 func hashmapNext(m unsafe.Pointer, it unsafe.Pointer, key, value unsafe.Pointer) bool
 
 func (v Value) MapRange() *MapIter {
-	if v.Kind() != Map {
+	iter := &MapIter{}
-		panic(&ValueError{Method: "MapRange", Kind: v.Kind()})
+	iter.Reset(v)
-	}
+	return iter
-
-	keyType := v.typecode.key()
-
-	keyTypeIsEmptyInterface := keyType.Kind() == Interface && keyType.NumMethod() == 0
-	shouldUnpackInterface := !keyTypeIsEmptyInterface && keyType.Kind() != String && !keyType.isBinary()
-
-	return &MapIter{
-		m:                  v,
-		it:                 hashmapNewIterator(),
-		unpackKeyInterface: shouldUnpackInterface,
-	}
 }
 
 type MapIter struct {
@@ -1142,6 +1131,10 @@ func (it *MapIter) Key() Value {
 	return it.key.Elem()
 }
 
+func (v Value) SetIterKey(iter *MapIter) {
+	v.Set(iter.Key())
+}
+
 func (it *MapIter) Value() Value {
 	if !it.valid {
 		panic("reflect.MapIter.Value called on invalid iterator")
@@ -1150,6 +1143,10 @@ func (it *MapIter) Value() Value {
 	return it.val.Elem()
 }
 
+func (v Value) SetIterValue(iter *MapIter) {
+	v.Set(iter.Value())
+}
+
 func (it *MapIter) Next() bool {
 	it.key = New(it.m.typecode.Key())
 	it.val = New(it.m.typecode.Elem())
@@ -1158,6 +1155,23 @@ func (it *MapIter) Next() bool {
 	return it.valid
 }
 
+func (iter *MapIter) Reset(v Value) {
+	if v.Kind() != Map {
+		panic(&ValueError{Method: "MapRange", Kind: v.Kind()})
+	}
+
+	keyType := v.typecode.key()
+
+	keyTypeIsEmptyInterface := keyType.Kind() == Interface && keyType.NumMethod() == 0
+	shouldUnpackInterface := !keyTypeIsEmptyInterface && keyType.Kind() != String && !keyType.isBinary()
+
+	*iter = MapIter{
+		m:                  v,
+		it:                 hashmapNewIterator(),
+		unpackKeyInterface: shouldUnpackInterface,
+	}
+}
+
 func (v Value) Set(x Value) {
 	v.checkAddressable()
 	v.checkRO()

src/reflect/all_test.go

@@ -381,8 +381,6 @@ func TestSetValue(t *testing.T) {
 	}
 }
 
-/*
-
 func TestMapIterSet(t *testing.T) {
 	m := make(map[string]any, len(valueTests))
 	for _, tt := range valueTests {
@@ -430,8 +428,6 @@ func TestMapIterSet(t *testing.T) {
 	}
 }
 
-*/
-
 func TestCanIntUintFloatComplex(t *testing.T) {
 	type integer int
 	type uinteger uint
@@ -7955,6 +7951,8 @@ func TestConvertibleTo(t *testing.T) {
 	}
 }
 
+*/
+
 func TestSetIter(t *testing.T) {
 	data := map[string]int{
 		"foo": 1,
@@ -8044,6 +8042,8 @@ func TestSetIter(t *testing.T) {
 	}
 }
 
+/*
+
 func TestMethodCallValueCodePtr(t *testing.T) {
 	m := ValueOf(Point{}).Method(1)
 	want := MethodValueCallCodePtr()

src/reflect/value.go

@@ -65,14 +65,26 @@ func (it *MapIter) Key() Value {
 	return Value{((*reflectlite.MapIter)(it)).Key()}
 }
 
+func (v Value) SetIterKey(iter *MapIter) {
+	v.Value.SetIterKey((*reflectlite.MapIter)(iter))
+}
+
 func (it *MapIter) Value() Value {
 	return Value{((*reflectlite.MapIter)(it)).Value()}
 }
 
+func (v Value) SetIterValue(iter *MapIter) {
+	v.Value.SetIterValue((*reflectlite.MapIter)(iter))
+}
+
 func (it *MapIter) Next() bool {
 	return ((*reflectlite.MapIter)(it)).Next()
 }
 
+func (iter *MapIter) Reset(v Value) {
+	(*reflectlite.MapIter)(iter).Reset(v.Value)
+}
+
 func (v Value) Set(x Value) {
 	v.Value.Set(x.Value)
 }