[bug/gnovm] arrays returned by functions should not be addressable

[deelawn]

This bug highlights a difference between gno and go. Here is an example

package main

import "crypto/sha256"

func main() {
	println(sha256.Sum256([]byte("x"))[:])
}

This will execute fine as gno code, but running it as go code yields
invalid operation: sha256.Sum256([]byte("x")) (value of type [32]byte) (slice of unaddressable value)

https://goplay.tools/snippet/MxwoBhtYZzz

[petar-dambovaliev]

I think, this might be a clearer example of the problem.

package main

func main() {
	foo()[:] // ./prog.go:4:2: invalid operation: foo() (value of type [2]byte) (slice of unaddressable value)
}

func foo() [2]byte {
	return [2]byte{1, 2}
}

[petar-dambovaliev]

This also works, when it shouldn't.

func main() {
	arr := &getArray()[0]
	println(arr)
}

func getArray() [3]int {
	return [3]int{1, 2, 3}
}

and this

type Point struct {
	X, Y int
}

func main() {
	arr := &[3]Point{{1, 2}, {3, 4}, {5, 6}}[0]
	println(arr)
}

[Kouteki]

Should mostly be fixed by Dylan. We can continue Dylan's work. Maxwell will take it up.