match lowering: Introduce a TestCase enum to replace most matching on PatKind by Nadrieril · Pull Request #121393 · rust-lang/rust (original) (raw)
Introduces TestCase that represents the specific outcome of a test. It complements TestKind which represents a test. In MatchPair::new() we select the appropriate TestCase for the pattern, and after that we almost never have to inspect the pattern directly during match lowering.
Together with #120904, this makes MatchPair into a standalone abstraction that hides the details of thir::Pat. This will become even truer in the next PR where I make TestCase handle or patterns. This opens the door to a lot of future simplifications.