Regression on main when allocating arrays of arrays

[LegNeato]

Minimal repro that fails to compile:

use spirv_std::spirv;

#[spirv(fragment)]
pub fn main() {
    let x = [[1; 2]; 1];
}

Bisects to 02cd324

It was found in #21 (comment) (assuming it is the same issue, but at least that is what I started with to get a repro)

[LegNeato]

@eddyb not sure if this will be fixed by your qptr stuff.

[eddyb]

Is this the error you're seeing?

error: cannot cast between pointer types
       from `*i32`
         to `*[i32; 2]`

With my various changes I also get:

error: error:0:0 - OpStore Pointer <id> '32[%32]' is not a logical pointer.
         OpStore %32 %33

And with a full move to qptr, something goes wrong with qptr.copy:

error: error:0:0 - Opcode CopyMemorySized requires one of these capabilities: Addresses 
         OpCopyMemorySized %29 %30 %uint_8

(and I'm not getting the kind of SPIR-T errors I would expect, either).

02cd324 shouldn't have broken anything like this, but that code is subtle and I am not exactly surprised.

My best guess is that something is being ambiguous about wanting access to the whole inner [_; 2] array, and instead it gets just the leaf field.

[LegNeato]

Yep, that's the error:

error: cannot cast between pointer types
       from `*i32`
         to `*[i32; 2]`

[LegNeato]

Also happens with arrays of vecs, which is more common: #189