[wgsl-in] Parse error for subtraction in array index

[fintelia]

This shader:

var<workgroup> a: array<u32, 64>;

fn foo() {
    let x = 1;
    let y = a[x-1];
}

Produces this error:

error: expected ']', found '-1'
  ┌─ a.wgsl:6:16
  │
6 │     let y = a[x-1];
  │                ^^ expected ']'

Could not parse WGSL

[jimblandy]

The issue here is that Naga treats -1 as a token, not an application of a unary - operator to the literal 1, so the expression is sort of like a[x 7]. This used to be standard behavior, but the WGSL specification changed.

[jimblandy]

This will be fixed by #4870.