WGSL doesn't type check values for vectors

[Timo-DK]

Having the following WGSL:

[[location 0]] var<in> a_uv : vec2<f32>;
[[location 0]] var<out> o_color : vec4<f32>;

fn main_frag() -> void {
  o_color = vec4<f32>(1, 0, 0, 1);
  return;
}
entry_point fragment as "main" = main_frag;

The values provided into the vector float 4 with the 4 integer values will be correctly parsed to the IR model:

Constant {
    name: None,
    specialization: None,
    inner: Sint(
        1,
    ),
    ty: Handle(4),
},
Constant {
    name: None,
    specialization: None,
    inner: Sint(
        0,
    ),
    ty: Handle(4),
},

The back-ends would now have to check if the vector where these constants are provided for is able to use them. I think it would be better to let the WGSL front-end check if the values in a vector are of the same Type as the composite they are in.

This is not something only applicable to vectors, and should have a general type check to ensure a correct IR model is delivered to the back-end.

[kvark]

Closed as a part of #59