W000 -- Checker Warning

W000 is the general warning code for non-fatal findings from the checker. The build continues; the warning points at something worth fixing.

What it covers

• Exhaustiveness findings (a match that may not cover every case).
• Problems found while checking catalog module bodies.

What to do

• Treat warnings as work items: the language requires exhaustive match expressions, so add the missing arms or a _ arm.
• --diagnostics=json includes warnings alongside errors, with the same code.

Notes

• Warnings do not stop the build and do not change the exit code.
• The current compiler does not reject every non-exhaustive match yet, so a clean build is not proof of exhaustiveness; write the arms anyway.