match on bool: exhaustiveness not checked

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
55/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
cpp, rust
Domain
compilers

Research direction

Start with the Rust frontend’s match exhaustiveness checking and its existing tests; use the issue’s a.rs example as the reproduction. Run the relevant test suite and confirm that a bool match with only a true arm is rejected as non-exhaustive, while an exhaustive match still passes.

Written by the indexing model from the issue text.

Description

fn a(y: bool) {
    match y {
        true => (),
    }
}

this compiles @ 2e8c317e34dc5531ca3e7927e2abfdbce497c646 although we have no false arm 😅

rustc:

error[E0004]: non-exhaustive patterns: `false` not covered
 --> a.rs:2:11
  |
2 |     match y {
  |           ^ pattern `false` not covered
  |
  = note: the matched value is of type `bool`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
  |
3 ~         true => (),
4 ~         false => todo!(),
  |

error: aborting due to 2 previous errors
Dominant language
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