gistfile1.txt

test/ in GOPATH/src

test/main.go
test/foo/bar.go

-- test/main.go --
package main   

import "test/foo"

func main() {
	a := foo.Test()
	println(a.Boo())
}

-- test/foo/bar.go --
package foo       

type Bar interface {
	Boo() string
}

func Test() Bar { return make(tst) }

type tst map[string]interface{}

func (r tst) Boo() string { return "Boo!" }

walk [7fafa90f8128]
. MAKE l(6) tc(1)
./main.go:3: undefined: foo.tst
./main.go:6: tempname called with nil type
./main.go:6: internal compiler error: walkexpr: switch 1 unknown op MAKE l(6) tc(1)