[wgsl-in] Align attribute not being propagated to struct alignment

[teoxoy]

With the changes in gfx-rs/naga#1812 this issue became apparent.

For instance the following example fails validation but shouldn't.

struct S {
    @align(16) // <- should propagate alignment to struct here
    a: u32,
}

struct Test {
    a: u32,
    b: S, // <- validation fails here because b has offset 4 but shouldn't since alignment of S should be 16
}

This is because the layouter is not aware of overridden alignment of struct members.

https://github.com/gfx-rs/naga/blob/43cd0eceddfac4c44c9a4fc4e9d156dfd1abba57/src/proc/layouter.rs#L187-L204

We most likely have to add alignment information in the IR (either on the struct or struct members).

[Swoorup]

Any timeline or updates on this issue? It becomes especially tedious manually adding padding with uniform buffers as they have strict requirement.s