cmd/compile: failure to reject initialization loop

[mdempsky]

cmd/compile accepts this bit of code, while go/types and gccgo reject it as an initialization cycle ("A refers to A"):

var A = func() int {
	if false {
		return A
	}
	return 0
}()

https://play.golang.org/p/jpUoGbyJqX

Related #21750. The common issue here is probably that we're performing initialization order analysis based on the optimized/inlined functions rather than the original Go source.

/cc @griesemer

[griesemer]

Marking 1.10 so it stays on radar.

[odeke-em]

Thanks for the report @mdempsky! Commenting here to add this to my priority list or at least radar, for Go1.12.