diff options
Diffstat (limited to 'compiler/rustc_pattern_analysis/src/usefulness.rs')
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/usefulness.rs | 14 |
1 files changed, 5 insertions, 9 deletions
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs index 092e752e977..bcc734dc81c 100644 --- a/compiler/rustc_pattern_analysis/src/usefulness.rs +++ b/compiler/rustc_pattern_analysis/src/usefulness.rs @@ -466,13 +466,9 @@ //! first pattern of a row in the matrix is an or-pattern, we expand it by duplicating the rest of //! the row as necessary. This is handled automatically in [`Matrix`]. //! -//! This makes usefulness tracking subtle, because we also want to compute whether an alternative -//! of an or-pattern is redundant, e.g. in `Some(_) | Some(0)`. We track usefulness of each -//! subpattern by interior mutability in [`DeconstructedPat`] with `set_useful`/`is_useful`. -//! -//! It's unfortunate that we have to use interior mutability, but believe me (Nadrieril), I have -//! tried [other](https://github.com/rust-lang/rust/pull/80104) -//! [solutions](https://github.com/rust-lang/rust/pull/80632) and nothing is remotely as simple. +//! This makes usefulness tracking subtle, because we also want to compute whether an alternative of +//! an or-pattern is redundant, e.g. in `Some(_) | Some(0)`. We therefore track usefulness of each +//! subpattern of the match. //! //! //! @@ -1462,8 +1458,8 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>( /// The core of the algorithm. /// /// This recursively computes witnesses of the non-exhaustiveness of `matrix` (if any). Also tracks -/// usefulness of each row in the matrix (in `row.useful`). We track usefulness of each -/// subpattern using interior mutability in `DeconstructedPat`. +/// usefulness of each row in the matrix (in `row.useful`). We track usefulness of each subpattern +/// in `mcx.useful_subpatterns`. /// /// The input `Matrix` and the output `WitnessMatrix` together match the type exhaustively. /// |