cmd/compile: function compiles OK with no return statement

[rogpeppe]

commit 1cbec68

The following program compiles and runs, but it should complain that there's no return statement in f:

package main

func main() {
	_ = f("")
}

func f(s string) string {
	for range s {
	}
}

[randall77]

This is kind of a corner case in the definition of terminating statements.

A "for" statement in which:
there are no "break" statements referring to the "for" statement, and
the loop condition is absent.

Technically that for statement qualifies, so no return after it is needed. There should maybe be an exception for a for range statement?

go1.17 gets this correct (it gives an error).

[gopherbot]

Change https://golang.org/cl/356189 mentions this issue: cmd/compile: make for loops with range statements terminating

[griesemer]

Nice find!

[gopherbot]

Change https://golang.org/cl/356411 mentions this issue: go/types, types2: add test case for missing return