cmd/compile: error for unexpected return values does not say 'return'

[rsc]

p1% cat /tmp/x.go
package p

func f0_2()            { return 1, 2 }
func f0_1()            { return 1 }
func f1_0() int        { return }
func f1_2() int        { return 1, 2 }
func f2_0() (int, int) { return }
func f2_1() (int, int) { return 1 }
p1% go tool compile /tmp/x.go
/tmp/x.go:3:33: no result values expected   <<<
/tmp/x.go:4:33: no result values expected   <<<
/tmp/x.go:5:26: not enough return values
	have ()
	want (int)
/tmp/x.go:6:36: too many return values
	have (number, number)
	want (int)
/tmp/x.go:7:26: not enough return values
	have ()
	want (int, int)
/tmp/x.go:8:33: not enough return values
	have (number)
	want (int, int)
p1% 

The marked messages that say 'result values' should be rewritten to say 'return values',
both for consistency with the others and for clarity.

The simplest fix is probably to stop treating f0_1 and f0_2 as a special case
and let the general 'too many return values' printer handle them, just like
f1_0 and f2_0` are not special cases and are handled by the general 'not enough return values' printer.

I know there's still plenty of generics work left in the type checker.
I can take care of this one myself this week.

[gopherbot]

Change https://golang.org/cl/379116 mentions this issue: cmd/compile, go/types: restore 'too many return values' error for func with no results