spec: clarify what gets passed to a variadic function when the call has no arguments #7073
Description
Given the program
package main
import "fmt"
func f(x ..int) {
fmt.Println(x)
}
func main() {
f()
}
the binary procuded by 6g prints [] not <nil>. The spec says the call passes a
"new slice", whatever that is. In fact, it passes an empty slice. Should it
pass nil instead? Regardless, the spec should be clearer.
Clear this up for 1.3. Outsiders are writing compilers.