feat(wgsl-in): parse diagnostic(…) attributes on fns

[ErichDonGubler]

Connections

• Depends on Emit unimplemented errors for several @diagnostic(…) attribute parse sites #6533.
• Partially resolves Support diagnostic filters in WGSL (i.e., diagnostic(…)) #5320.

Description

Building on #6148 and #6533, we use all the plumbing we made for tracking diagnostic rules, and add a (successful) parse path for @diagnostic(…) fn function() { … }. This and #6148's parse paths are what I've observed to be the next most common places for users to apply diagnostic filtering, by a wide margin. I expect we will

Testing

• Demonstrate that the following CTS cases work:
  • webgpu:shader,validation,parse,diagnostic:valid_locations:*
    • …:type="attribute";location="function"
  • webgpu:shader,validation,parse,diagnostic:duplicate_attribute_same_location:*
    • …:loc="function";same_rule=true: ✅
    • …:loc="function";same_rule=false: ❌ → ✅
  • webgpu:shader,validation,parse,diagnostic:conflicting_attribute_different_location:* Only tests statement-position attributes. 🙁
  • At least one case in webgpu:shader,validation,parse,diagnostic:diagnostic_scoping:*, specific case TBD. Only tests statement-position attributes. 🙁
• Port a meaningful subset of the above to our own Naga test suite, to prevent the most impactful regressions. Punted for later.

Checklist

• Run cargo fmt.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[ErichDonGubler]

Populated the OP with test results.

[teoxoy]

LGTM