reflect: add Value.UnsafePointer method

This was added in Go 1.18.

src/reflect/value.go

@@ -135,16 +135,22 @@ func (v Value) IsNil() bool {
 // Pointer returns the underlying pointer of the given value for the following
 // types: chan, map, pointer, unsafe.Pointer, slice, func.
 func (v Value) Pointer() uintptr {
+	return uintptr(v.UnsafePointer())
+}
+
+// UnsafePointer returns the underlying pointer of the given value for the
+// following types: chan, map, pointer, unsafe.Pointer, slice, func.
+func (v Value) UnsafePointer() unsafe.Pointer {
 	switch v.Kind() {
 	case Chan, Map, Ptr, UnsafePointer:
-		return uintptr(v.pointer())
+		return v.pointer()
 	case Slice:
 		slice := (*sliceHeader)(v.value)
-		return uintptr(slice.data)
+		return slice.data
 	case Func:
-		panic("unimplemented: (reflect.Value).Pointer()")
+		panic("unimplemented: (reflect.Value).UnsafePointer()")
 	default: // not implemented: Func
-		panic(&ValueError{Method: "Pointer"})
+		panic(&ValueError{Method: "UnsafePointer"})
 	}
 }