Referencing a function without a return type yields an unknown identifier error.

[OptimisticPeach]

I had code which resembled the following:

fn foo() {
    return vec2<f32>(0.0, 0.0);
}

fn bar() {
    let qux = foo();
}

Note that I forgot a return type on foo. (This was much more difficult to spot at a glance in my actual code).

Validating the code with Naga fails with:

❯ cargo run example.wgsl
    Finished dev [unoptimized + debuginfo] target(s) in 0.23s
     Running `target\debug\naga.exe example.wgsl`
error: no definition in scope for identifier: 'foo'
  ┌─ example.wgsl:6:15
  │
6 │     let qux = foo();
  │               ^^^ unknown identifier

Could not parse WGSL
error: process didn't exit successfully: `target\debug\naga.exe example.wgsl` (exit code: 1)

Whereas I'd expect it to either:

• Error on foo containing a return statement while it returns nothing, or
• Tell me that foo returns nothing and assigning to a variable is foolish.