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encoding/json: simplify (*decodeState).indirect

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Removes an incorrect code comment and some superfluous variables.

The comment I removed says that struct fields which implement
Unmarshaler must be pointers, even if they're in an addressable
struct. That's not the case, and there's already a test in decode_test.go
that demonstrates as much.

Encoding/json has quite a few assignments of reflect.Values to extra
variables – things like "iv := v" when there's no need to make a copy. I
think these are left over from a previous version of the reflect API. If they
aren't wanted, I wouldn't mind going through the package and getting
rid of the rest of them.

R=rsc
CC=golang-dev
https://golang.org/cl/6318047
This commit is contained in:
Micah Stetson 2012-06-25 16:03:18 -04:00 committed by Russ Cox
parent 32a0cbb881
commit 51ff2ef409
1 changed files with 12 additions and 27 deletions
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39
src/pkg/encoding/json/decode.go
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@ -265,47 +265,32 @@ func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler,
v = v.Addr()
}
for {
var isUnmarshaler bool
if v.Type().NumMethod() > 0 {
// Remember that this is an unmarshaler,
// but wait to return it until after allocating
// the pointer (if necessary).
_, isUnmarshaler = v.Interface().(Unmarshaler)
}
// Load value from interface, but only if the result will be
// usefully addressable.
if iv := v; iv.Kind() == reflect.Interface && !iv.IsNil() {
e := iv.Elem()
if v.Kind() == reflect.Interface && !v.IsNil() {
e := v.Elem()
if e.Kind() == reflect.Ptr && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Ptr) {
v = e
continue
}
}
pv := v
if pv.Kind() != reflect.Ptr {
if v.Kind() != reflect.Ptr {
break
}
if pv.Elem().Kind() != reflect.Ptr && decodingNull && pv.CanSet() {
return nil, pv
if v.Elem().Kind() != reflect.Ptr && decodingNull && v.CanSet() {
break
}
if pv.IsNil() {
pv.Set(reflect.New(pv.Type().Elem()))
if v.IsNil() {
v.Set(reflect.New(v.Type().Elem()))
}
if isUnmarshaler {
// Using v.Interface().(Unmarshaler)
// here means that we have to use a pointer
// as the struct field. We cannot use a value inside
// a pointer to a struct, because in that case
// v.Interface() is the value (x.f) not the pointer (&x.f).
// This is an unfortunate consequence of reflect.
// An alternative would be to look up the
// UnmarshalJSON method and return a FuncValue.
return v.Interface().(Unmarshaler), reflect.Value{}
if v.Type().NumMethod() > 0 {
if unmarshaler, ok := v.Interface().(Unmarshaler); ok {
return unmarshaler, reflect.Value{}
}
}
v = pv.Elem()
v = v.Elem()
}
return nil, v
}