cmd/aefix/typecheck.go
func joinFunc(in, out []string) string {
	outs := ""
	if len(out) == 1 {
		outs = " " + out[0]
	} else if len(out) > 1 {
		outs = " (" + join(out) + ")"
	}
	return "func(" + join(in) + ")" + outs
}
func joinFunc(in, out []string) string {
	outs := ""
	if len(out) == 1 {
		outs = " " + out[0]
	} else if len(out) > 1 {
		outs = " (" + join(out) + ")"
	}
	return "func(" + join(in) + ")" + outs
}
// joinFunc is the inverse of splitFunc.