comment

Author: Nadrieril

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -949,12 +949,15 @@ struct Candidate<'pat, 'tcx> {
     has_guard: bool,
 
     /// All of these must be satisfied...
+    // Invariant: all the `MatchPair`s are recursively simplified.
     match_pairs: Vec<MatchPair<'pat, 'tcx>>,
 
     /// ...these bindings established...
+    // Invariant: not mutated during match tree construction.
     bindings: Vec<Binding<'tcx>>,
 
     /// ...and these types asserted...
+    // Invariant: not mutated during match tree construction.
     ascriptions: Vec<Ascription<'tcx>>,
 
     /// ...and if this is non-empty, one of these subcandidates also has to match...
@@ -1056,6 +1059,7 @@ pub(crate) struct MatchPair<'pat, 'tcx> {
     place: PlaceBuilder<'tcx>,
 
     // ... must match this pattern.
+    // Invariant: this pattern must be simplified, i.e. requires a test.
     pattern: &'pat Pat<'tcx>,
 
     /// Precomputed sub-match pairs.