Wgsl alias does not work when using from module

[Swoorup]

It appears that you can't use wgsl alias from a composable module. It works when using you are using from the make module file though.

composer
  .add_composable_module(ComposableModuleDescriptor {
      source: "alias Vec2 = vec2<f32>;",
      file_path: "valid.wgsl",
      as_name: Some("valid".to_owned()),
      ..Default::default()
  })
  .unwrap();

let module = composer
    .make_naga_module(NagaModuleDescriptor {
        source: r#"
      #import valid::Vec2;

      @group(0) @binding(1) var<uniform> position: Vec2;
    "#,
        file_path: "",
        ..Default::default()
    })
    .map_err(|err| println!("{}", err.emit_to_string(&composer)))
    .unwrap();

Here you get the error:

error: Composable module identifiers must not require substitution according to naga writeback rules: `Vec2`
  ┌─ valid.wgsl:1:1
  │
1 │ 
  │ ^ Composable module identifiers must not require substitution according to naga writeback rules: `Vec2`

[robtfm]

i haven't used aliases at all, so i wouldn't t expect this to work without some changes.

that said, this error is due to the '2' on the end. if you call it VecTwo you might get it to work, or at least get another error. we do some translations to allow most items (not struct members, and apparently not aliases) to end in numbers, and probably need to handle aliases explicitly as well in the same way.

but i suspect there will be more changes required to support aliases, maybe for internal use in a module and almost certainly for importing them into another module.

i'm not sure importing them would ever work, since i'm not sure languages other than wgsl have alias support.

[Swoorup]

Ugh, you are right. I renamed Vec2 to Vivek and I got

error: unknown type: 'Vivek'
  ┌─ :4:53
  │
4 │           @group(0) @binding(1) var<uniform> valid: Vivek;
  │                                                     ^^^^^ unknown type
  │
  = unknown type: 'Vivek'

[Swoorup]

but i suspect there will be more changes required to support aliases, maybe for internal use in a module and almost certainly for importing them into another module.

i'm not sure importing them would ever work, since i'm not sure languages other than wgsl have alias support.

I'd mostly like to use then as semi- new types for things like alias worldpoint = vec2<f32> rather, structs have stricter requirements (16 bytes alignment).

For other languages I suppose, we just output the types they alias?

[robtfm]

do type aliases in wgsl give you type safety? the docs are unclear but i suspect not. and if not i guess you could just include the aliases everywhere you want to use them...

[Swoorup]

It doesn't. But its better than nothing. 😄