cmd/compile: deferring nil function panicked too early on Wasm and AIX

[cherrymui]

What version of Go are you using (go version)?

tip (06b12e6)

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

js/wasm, and aix/ppc64

What did you do?

https://play.golang.org/p/6zD83-Dhd1P

package main

var x = 0

func main() {
	defer func() { recover(); println(x) }()
	f()
}

func f() {
	var nilf func()
	defer nilf()
	x = 1
}

What did you expect to see?

The spec requires (https://golang.org/ref/spec#Defer_statements)

If a deferred function value evaluates to nil, execution panics when the function is invoked, not when the "defer" statement is executed.

So in the program above, the assignment x=1 should go through, so it should print 1.

What did you see instead?

Print 0 on Wasm and AIX.

I'll send a CL shortly.

cc @danscales

[gopherbot]

Change https://golang.org/cl/201297 mentions this issue: cmd/compile: on Wasm and AIX, let deferred nil function panic at invocation