What steps will reproduce the problem?
http://play.golang.org/p/epXpwk0s4s

What is the expected output?
Something like this:
http://play.golang.org/p/Dk0l6fTj01

What do you see instead?
{"bar":{},"foo":{}}

Which compiler are you using (5g, 6g, 8g, gccgo)?


Which operating system are you using?
Linux (Ubuntu 12.04, 3.2.0-38-generic)

Which version are you using?  (run 'go version')
go version go1.0.3
go version devel +5260abd6df41 Sat Mar 30 19:05:00 2013 +0800 linux/amd64

Please provide any additional information below.
I think it's not intuitive behaviour. fmt prints errors without problems, why json not?