What does 'go version' print?
go version go1.3.1 linux/amd64

What steps reproduce the problem?
1. Create a struct type with a field of type *int64
2. Init with a non-nil value for that field
3. Encode using json.Marshal
4. Decode result using json.Unmarshal

http://play.golang.org/p/fWLSVv9hxT

Also discussed:
groups.google.com/d/msg/golang-nuts/BTNKGipB7zs/Ub3FDleTnlkJ
groups.google.com/forum/#!topic/golang-nuts/mr49_7W9CKM

What happened?
Encountered decode error unmarshalling quoted (string) field value ("err
unmarshalling json: cannot unmarshal number into Go value of type string")

What should have happened instead?
Decoded int64 string value into a *int64 without error.

Please provide any additional information below.
encoding/json/encode.go
 699    func (pe *ptrEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
   700      if v.IsNil() {
   701          e.WriteString("null")
   702          return
   703      }
   704      pe.elemEnc(e, v.Elem(), false)
   705  }

If changed to (lines 699, 704)
 699    func (pe *ptrEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
   700      if v.IsNil() {
   701          e.WriteString("null")
   702          return
   703      }
   704      pe.elemEnc(e, v.Elem(), quoted)
   705  }

corrects the issue. As the array, slice, struct, and map encoders ignore the quoted
parameter, this should still result in correct json encoding in all existing code, while
printing strings for numeric and bool values (as a user probably expects when adding the
string tag option)