We currently do not support the @diagnostic(…) attribute/diagnostic(…) directive (AKA "diagnostic filters" in the WebGPU spec.). This is a rather complicated subsystem, but it's exciting to have robust management of diagnostics in WGSL a la Rust. An example of how this is used from the spec.:

EXAMPLE: Global diagnostic filter for derivative uniformity

diagnostic(off,derivative_uniformity);
var<private> d: f32;
fn helper() -> vec4<f32> {
  if (d < 0.5) {
    // The derivative_uniformity diagnostic is disabled here
    // by the global diagnostic filter.
    return textureSample(t,s,vec2(0,0));
  } else {
    // The derivative_uniformity diagnostic is set to 'warning' severity.
    @diagnostic(warning,derivative_uniformity) {
      return textureSample(t,s,vec2(0,0));
    }
  }
  return vec4(0.0);
}

Relevant part of the spec.: Diagnostics, section 2.3

An initial implementation of this should include the derivative_uniformity rule, as the only current example of filterable trigger rules that can be managed per the spec.

Parse paths that we need to support to be spec.-compliant:

• Directive: WGSL: Implement diagnostic(…); directives and derivative_uniformity triggering rule #6148
• Attributes placements (pasted from the spec.):
  • Beginning of a compound statement.
  • Beginning of a function declaration: feat(wgsl-in): parse diagnostic(…) attributes on fns #6353
  • Beginning of an if statement.
  • Beginning of a switch statement.
  • Beginning of a switch_body.
  • Beginning of a loop statement.
  • Beginning of a while statement.
  • Beginning of a for statement.
  • Immediately before the opening brace ('{') of the loop body of a loop, while, or for loop.
  • Beginning of a continuing_compound_statement.