reflect: add Go 1.24 iter.Seq[2] methods

src/reflect/iter.go

@@ -0,0 +1,166 @@
+// Copyright 2024 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 reflect
+
+import "iter"
+
+func rangeNum[T int8 | int16 | int32 | int64 | int |
+	uint8 | uint16 | uint32 | uint64 | uint |
+	uintptr, N int64 | uint64](v N) iter.Seq[Value] {
+	return func(yield func(v Value) bool) {
+		// cannot use range T(v) because no core type.
+		for i := T(0); i < T(v); i++ {
+			if !yield(ValueOf(i)) {
+				return
+			}
+		}
+	}
+}
+
+// Seq returns an iter.Seq[Value] that loops over the elements of v.
+// If v's kind is Func, it must be a function that has no results and
+// that takes a single argument of type func(T) bool for some type T.
+// If v's kind is Pointer, the pointer element type must have kind Array.
+// Otherwise v's kind must be Int, Int8, Int16, Int32, Int64,
+// Uint, Uint8, Uint16, Uint32, Uint64, Uintptr,
+// Array, Chan, Map, Slice, or String.
+func (v Value) Seq() iter.Seq[Value] {
+	// TODO: canRangeFunc
+	// if canRangeFunc(v.typ()) {
+	// 	return func(yield func(Value) bool) {
+	// 		rf := MakeFunc(v.Type().In(0), func(in []Value) []Value {
+	// 			return []Value{ValueOf(yield(in[0]))}
+	// 		})
+	// 		v.Call([]Value{rf})
+	// 	}
+	// }
+	switch v.Kind() {
+	case Int:
+		return rangeNum[int](v.Int())
+	case Int8:
+		return rangeNum[int8](v.Int())
+	case Int16:
+		return rangeNum[int16](v.Int())
+	case Int32:
+		return rangeNum[int32](v.Int())
+	case Int64:
+		return rangeNum[int64](v.Int())
+	case Uint:
+		return rangeNum[uint](v.Uint())
+	case Uint8:
+		return rangeNum[uint8](v.Uint())
+	case Uint16:
+		return rangeNum[uint16](v.Uint())
+	case Uint32:
+		return rangeNum[uint32](v.Uint())
+	case Uint64:
+		return rangeNum[uint64](v.Uint())
+	case Uintptr:
+		return rangeNum[uintptr](v.Uint())
+	case Pointer:
+		if v.Elem().Kind() != Array {
+			break
+		}
+		return func(yield func(Value) bool) {
+			v = v.Elem()
+			for i := 0; i < v.Len(); i++ {
+				if !yield(ValueOf(i)) {
+					return
+				}
+			}
+		}
+	case Array, Slice:
+		return func(yield func(Value) bool) {
+			for i := 0; i < v.Len(); i++ {
+				if !yield(ValueOf(i)) {
+					return
+				}
+			}
+		}
+	case String:
+		return func(yield func(Value) bool) {
+			for i := range v.String() {
+				if !yield(ValueOf(i)) {
+					return
+				}
+			}
+		}
+	case Map:
+		return func(yield func(Value) bool) {
+			i := v.MapRange()
+			for i.Next() {
+				if !yield(i.Key()) {
+					return
+				}
+			}
+		}
+	case Chan:
+		return func(yield func(Value) bool) {
+			for value, ok := v.Recv(); ok; value, ok = v.Recv() {
+				if !yield(value) {
+					return
+				}
+			}
+		}
+	}
+	panic("reflect: " + v.Type().String() + " cannot produce iter.Seq[Value]")
+}
+
+// Seq2 returns an iter.Seq2[Value, Value] that loops over the elements of v.
+// If v's kind is Func, it must be a function that has no results and
+// that takes a single argument of type func(K, V) bool for some type K, V.
+// If v's kind is Pointer, the pointer element type must have kind Array.
+// Otherwise v's kind must be Array, Map, Slice, or String.
+func (v Value) Seq2() iter.Seq2[Value, Value] {
+	// TODO: canRangeFunc2
+	// if canRangeFunc2(v.typ()) {
+	// 	return func(yield func(Value, Value) bool) {
+	// 		rf := MakeFunc(v.Type().In(0), func(in []Value) []Value {
+	// 			return []Value{ValueOf(yield(in[0], in[1]))}
+	// 		})
+	// 		v.Call([]Value{rf})
+	// 	}
+	// }
+	switch v.Kind() {
+	case Pointer:
+		if v.Elem().Kind() != Array {
+			break
+		}
+		return func(yield func(Value, Value) bool) {
+			v = v.Elem()
+			for i := 0; i < v.Len(); i++ {
+				if !yield(ValueOf(i), v.Index(i)) {
+					return
+				}
+			}
+		}
+	case Array, Slice:
+		return func(yield func(Value, Value) bool) {
+			for i := 0; i < v.Len(); i++ {
+				if !yield(ValueOf(i), v.Index(i)) {
+					return
+				}
+			}
+		}
+	case String:
+		return func(yield func(Value, Value) bool) {
+			for i, v := range v.String() {
+				if !yield(ValueOf(i), ValueOf(v)) {
+					return
+				}
+			}
+		}
+	case Map:
+		return func(yield func(Value, Value) bool) {
+			i := v.MapRange()
+			for i.Next() {
+				if !yield(i.Key(), i.Value()) {
+					return
+				}
+			}
+		}
+	}
+	panic("reflect: " + v.Type().String() + " cannot produce iter.Seq2[Value, Value]")
+}

src/reflect/type.go

@@ -329,6 +329,12 @@ type Type interface {
 	// OverflowUint reports whether the uint64 x cannot be represented by type t.
 	// It panics if t's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
 	OverflowUint(x uint64) bool
+
+	// CanSeq reports whether a [Value] with this type can be iterated over using [Value.Seq].
+	CanSeq() bool
+
+	// CanSeq2 reports whether a [Value] with this type can be iterated over using [Value.Seq2].
+	CanSeq2() bool
 }
 
 type rawType struct {
@@ -359,6 +365,32 @@ func (t *rawType) AssignableTo(u Type) bool {
 	return t.RawType.AssignableTo(&(u.(*rawType).RawType))
 }
 
+func (t *rawType) CanSeq() bool {
+	switch t.Kind() {
+	case Int8, Int16, Int32, Int64, Int, Uint8, Uint16, Uint32, Uint64, Uint, Uintptr, Array, Slice, Chan, String, Map:
+		return true
+	case Func:
+		return false // TODO: implement canRangeFunc
+		// return canRangeFunc(&t.)
+	case Pointer:
+		return t.Elem().Kind() == Array
+	}
+	return false
+}
+
+func (t *rawType) CanSeq2() bool {
+	switch t.Kind() {
+	case Array, Slice, String, Map:
+		return true
+	case Func:
+		return false // TODO: implement canRangeFunc2
+		// return canRangeFunc2(&t.t)
+	case Pointer:
+		return t.Elem().Kind() == Array
+	}
+	return false
+}
+
 func (t *rawType) ConvertibleTo(u Type) bool {
 	panic("unimplemented: (reflect.Type).ConvertibleTo()")
 }