fix(const_eval): don't panic when a vecN constructor's arg. count is less than N

[ErichDonGubler]

Connections

• Fixes the crash noted in naga: index out of bound in constant_evaluator.rs:217 #6506.

Description

From my comment in the issue:

… component_wise_* functions in the const_eval module presume that a Compose expression of a Vector of N elements (in the OP example, vec4) has N arguments in the IR.

Stop presuming this, and return an error gracefully if the condition is violated.

Testing

Tested manually.

Checklist

• Run cargo fmt.
• Run taplo format.
• 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.

[teoxoy]

Nice!