`unreachable_pattern` could get more specific if the preempting pattern resembles a `const`

matchallways picks the first arm if matching value is not defined/unknown.
I was using constto define the values for the arms.
But the const were places inside the main() and the match expression was in a separate function.

I tried this code:

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=4b8fce2e782604f738c4fb9229b2a29b

Uncommenting the first 2 const gives the wanted results.

I expected to see this happen:

That the compiler finds the const values or stop compiling because the matching values are unknown.

Instead, this happened:

It just compiles.
But it gives some warnings like warning: unreachable pattern.
It just runs but with the wrong values.

See play link. See the behavior on all the versions "Stable", "Beta" and "Nightly".

Start by running the linked Rust Playground reproducer on Stable, Beta, and Nightly, including the versions with the first two const declarations uncommented. The issue names no source files or tests; done should establish whether unknown const values in a separate function should change match analysis or produce a compilation error, and should include regression coverage if a behavior change is accepted.