The buf below shouldn't escape to the heap.

package main

func nothing() {
}

func f(b []byte) []byte { // leaking param: b
        b[0] = 'H'
        b[1] = 'i'
        nothing() // (force f to not inline.)
        return b[:2]
}

func main() {
        var buf [10]byte // moved to heap: buf
        hi := f(buf[:]) // buf escapes to heap
        for i, c := range hi {
                println(i, c)
        }
}

$ go tool 6g -s -m e.go
e.go:3: can inline nothing
e.go:9: inlining call to nothing
e.go:14: moved to heap: buf
e.go:6: leaking param: b
e.go:15: buf escapes to heap