[Migrated] ZST's in structs cause invalid pointer casts

Issue automatically imported from old repo: https://github.com/EmbarkStudios/rust-gpu/issues/1037
Old labels: t: bug,s: qptr may fix
Originally creatd by TrueDoctor on 2023-04-18T16:53:55Z

Expected Behaviour

The code should compile

Example & Steps To Reproduce

code:

 #[spirv(fragment)] 
 pub fn main(x: (usize, ())) {
    drop(&x.1); 
 }

result:

error: Cannot cast between pointer types
  --> examples/shaders/simplest-shader/src/lib.rs:44:55
   |
44 | #[spirv(fragment)] pub fn main(x: (usize, ())) { drop(&x.1); }
   |                                                       ^^^^
   |
   = note: from: *u32
   = note: to: *u8

error: Cannot offset a pointer to an arbitrary element
  --> examples/shaders/simplest-shader/src/lib.rs:44:55
   |
44 | #[spirv(fragment)] pub fn main(x: (usize, ())) { drop(&x.1); }
   |                                                       ^^^^

error: Cannot cast between pointer types
  --> examples/shaders/simplest-shader/src/lib.rs:44:50
   |
44 | #[spirv(fragment)] pub fn main(x: (usize, ())) { drop(&x.1); }
   |                                                  ^^^^^^^^^^
   |
   = note: from: *u8
   = note: to: *struct () {  }

System Info

• Rust: [e.g. 1.49.0-nightly (1eaadebb3 2020-10-21)]
• OS: linux 6.2.9-arch1-1
• GPU: Intel Iris Plus Graphics G7

examples/shaders/simplest-shader/src/lib.rs の再現コードから始め、特に #[spirv(fragment)] 関数と x.1 への参照を確認します。例を実行し、ポインターキャストと任意オフセットのエラーを調査します。サイズ 0 のタプルフィールドを含むこの一見有効な struct が、これらのエラーなしでコンパイルできれば完了です。