Gc crashes on the following program: ``` go package a import "fmt" const n = fmt ``` ``` treecopy [0xc820209d40] . PACK l(2) a.fmt tmp.go:3: internal compiler error: treecopy Name ``` This is a regression from Go1.4, it produced a sensible error message. go version devel +514014c Thu Jun 18 15:54:35 2015 +0200 linux/amd64