encoding/json: cleanup leftover redundant variables.

Those variables come from ancient times when reflect.Value was
an interface.

R=dave, rsc
CC=golang-dev
https://golang.org/cl/6946059

src/pkg/encoding/json/decode.go

@@ -125,13 +125,12 @@ func (d *decodeState) unmarshal(v interface{}) (err error) {
 	}()
 
 	rv := reflect.ValueOf(v)
-	pv := rv
-	if pv.Kind() != reflect.Ptr || pv.IsNil() {
+	if rv.Kind() != reflect.Ptr || rv.IsNil() {
 		return &InvalidUnmarshalError{reflect.TypeOf(v)}
 	}
 
 	d.scan.reset()
-	// We decode rv not pv.Elem because the Unmarshaler interface
+	// We decode rv not rv.Elem because the Unmarshaler interface
 	// test must be applied at the top level of the value.
 	d.value(rv)
 	return d.savedError
@@ -423,17 +422,12 @@ func (d *decodeState) object(v reflect.Value) {
 	v = pv
 
 	// Decoding into nil interface?  Switch to non-reflect code.
-	iv := v
-	if iv.Kind() == reflect.Interface {
-		iv.Set(reflect.ValueOf(d.objectInterface()))
+	if v.Kind() == reflect.Interface {
+		v.Set(reflect.ValueOf(d.objectInterface()))
 		return
 	}
 
 	// Check type of target: struct or map[string]T
-	var (
-		mv reflect.Value
-		sv reflect.Value
-	)
 	switch v.Kind() {
 	case reflect.Map:
 		// map must have string type
@@ -442,17 +436,15 @@ func (d *decodeState) object(v reflect.Value) {
 			d.saveError(&UnmarshalTypeError{"object", v.Type()})
 			break
 		}
-		mv = v
-		if mv.IsNil() {
-			mv.Set(reflect.MakeMap(t))
+		if v.IsNil() {
+			v.Set(reflect.MakeMap(t))
 		}
 	case reflect.Struct:
-		sv = v
 	default:
 		d.saveError(&UnmarshalTypeError{"object", v.Type()})
 	}
 
-	if !mv.IsValid() && !sv.IsValid() {
+	if !v.IsValid() {
 		d.off--
 		d.next() // skip over { } in input
 		return
@@ -484,8 +476,8 @@ func (d *decodeState) object(v reflect.Value) {
 		var subv reflect.Value
 		destring := false // whether the value is wrapped in a string to be decoded first
 
-		if mv.IsValid() {
-			elemType := mv.Type().Elem()
+		if v.Kind() == reflect.Map {
+			elemType := v.Type().Elem()
 			if !mapElem.IsValid() {
 				mapElem = reflect.New(elemType).Elem()
 			} else {
@@ -494,7 +486,7 @@ func (d *decodeState) object(v reflect.Value) {
 			subv = mapElem
 		} else {
 			var f *field
-			fields := cachedTypeFields(sv.Type())
+			fields := cachedTypeFields(v.Type())
 			for i := range fields {
 				ff := &fields[i]
 				if ff.name == key {
@@ -506,7 +498,7 @@ func (d *decodeState) object(v reflect.Value) {
 				}
 			}
 			if f != nil {
-				subv = sv
+				subv = v
 				destring = f.quoted
 				for _, i := range f.index {
 					if subv.Kind() == reflect.Ptr {
@@ -519,7 +511,7 @@ func (d *decodeState) object(v reflect.Value) {
 				}
 			} else {
 				// To give a good error, a quick scan for unexported fields in top level.
-				st := sv.Type()
+				st := v.Type()
 				for i := 0; i < st.NumField(); i++ {
 					f := st.Field(i)
 					if f.PkgPath != "" && strings.EqualFold(f.Name, key) {
@@ -546,8 +538,8 @@ func (d *decodeState) object(v reflect.Value) {
 		}
 		// Write value back to map;
 		// if using struct, subv points into struct already.
-		if mv.IsValid() {
-			mv.SetMapIndex(reflect.ValueOf(key), subv)
+		if v.Kind() == reflect.Map {
+			v.SetMapIndex(reflect.ValueOf(key), subv)
 		}
 
 		// Next token must be , or }.