code review 180112: Allow %p on reference types, for debugging.

Allow %p on reference types, for debugging.
(Also fix case sensitivity in test for PTR inside fmt_test.go)
Fixes issue 441.

[r, 2009-12-22 05:18:10]

Hello  (cc: golang-dev@googlegroups.com),

I'd like you to review the following change.

[iant, 2009-12-22 05:43:44]

LGTM

[r, 2009-12-22 06:02:04]

*** Submitted as http://code.google.com/p/go/source/detail?r=e526f4d7d93c ***

Allow %p on reference types, for debugging.
(Also fix case sensitivity in test for PTR inside fmt_test.go)
Fixes issue 441.

R=rsc, iant
CC=golang-dev
http://codereview.appspot.com/180112

[rsc, 2009-12-22 16:49:16]

http://codereview.appspot.com/180112/diff/8/1007
File src/pkg/fmt/print.go (right):

http://codereview.appspot.com/180112/diff/8/1007#newcode811
src/pkg/fmt/print.go:811: p.fmt.fmt_uX64(uint64(field.Addr()))
Addr() is a pointer to the chan, map, or slice value,
not the chan, map, or slice value itself.

I think here you want

switch v := field.(type) {
case interface { Get() uintptr }:
    ...
default:
    goto badtype
}

That will handle PtrValue and ChanValue now,
and then MapValue if you add MapValue.Get
(can just copy ChanValue.Get).
You could add SliceValue.Get too, though 
perhaps the %p format of a SliceValue should
show len and cap too.

If %p formats SliceValue it should probably also
format StringValue.