Coming here from https://go-review.googlesource.com/c/go/+/437216/2..3/test/closure3.dir/main.go#b255.

Currently, the compiler names the closures base on the outer function:

package main

func main() {
	a := 2
	if r := func(x int) int {
		b := 3
		return func(y int) int {
			c := 5
			return func(z int) int {
				return a*x + b*y + c*z
			}(10)
		}(100)
	}(1000); r != 2350 {
		panic("r != 2350")
	}
}

For:

return func(z int) int {
	return a*x + b*y + c*z
}(10)

Unified IR generates main.func1.func2, while the old frontend generates main.func1.2. The discrepancy happens when calling ir.NameClosure. The old frontend use the immediate outer function (return func(y int) int { ... }) as outer function, while Unified IR use the outer most (func main() { ... }).

@mdempsky think that the func prefix may not be necessary, and we can remove it.