diff options
Diffstat (limited to 'compiler/rustc_pattern_analysis/src/usefulness.rs')
| -rw-r--r-- | compiler/rustc_pattern_analysis/src/usefulness.rs | 34 |
1 files changed, 15 insertions, 19 deletions
diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs index 76dc338e71c..6535afcc398 100644 --- a/compiler/rustc_pattern_analysis/src/usefulness.rs +++ b/compiler/rustc_pattern_analysis/src/usefulness.rs @@ -543,13 +543,11 @@ //! recurse into subpatterns. That second part is done through [`PlaceValidity`], most notably //! [`PlaceValidity::specialize`]. //! -//! Having said all that, in practice we don't fully follow what's been presented in this section. -//! Let's call "toplevel exception" the case where the match scrutinee itself has type `!` or -//! `EmptyEnum`. First, on stable rust, we require `_` patterns for empty types in all cases apart -//! from the toplevel exception. The `exhaustive_patterns` and `min_exaustive_patterns` allow -//! omitting patterns in the cases described above. There's a final detail: in the toplevel -//! exception or with the `exhaustive_patterns` feature, we ignore place validity when checking -//! whether a pattern is required for exhaustiveness. I (Nadrieril) hope to deprecate this behavior. +//! Having said all that, we don't fully follow what's been presented in this section. For +//! backwards-compatibility, we ignore place validity when checking whether a pattern is required +//! for exhaustiveness in two cases: when the `exhaustive_patterns` feature gate is on, or when the +//! match scrutinee itself has type `!` or `EmptyEnum`. I (Nadrieril) hope to deprecate this +//! exception. //! //! //! @@ -709,18 +707,19 @@ //! I (Nadrieril) prefer to put new tests in `ui/pattern/usefulness` unless there's a specific //! reason not to, for example if they crucially depend on a particular feature like `or_patterns`. -use self::PlaceValidity::*; -use crate::constructor::{Constructor, ConstructorSet, IntRange}; -use crate::pat::{DeconstructedPat, PatId, PatOrWild, WitnessPat}; -use crate::{Captures, MatchArm, PatCx, PrivateUninhabitedField}; +use std::fmt; + +#[cfg(feature = "rustc")] +use rustc_data_structures::stack::ensure_sufficient_stack; use rustc_hash::{FxHashMap, FxHashSet}; use rustc_index::bit_set::BitSet; use smallvec::{smallvec, SmallVec}; -use std::fmt; use tracing::{debug, instrument}; -#[cfg(feature = "rustc")] -use rustc_data_structures::stack::ensure_sufficient_stack; +use self::PlaceValidity::*; +use crate::constructor::{Constructor, ConstructorSet, IntRange}; +use crate::pat::{DeconstructedPat, PatId, PatOrWild, WitnessPat}; +use crate::{Captures, MatchArm, PatCx, PrivateUninhabitedField}; #[cfg(not(feature = "rustc"))] pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R { f() @@ -952,13 +951,10 @@ impl<Cx: PatCx> PlaceInfo<Cx> { self.is_scrutinee && matches!(ctors_for_ty, ConstructorSet::NoConstructors); // Whether empty patterns are counted as useful or not. We only warn an empty arm unreachable if // it is guaranteed unreachable by the opsem (i.e. if the place is `known_valid`). - let empty_arms_are_unreachable = self.validity.is_known_valid() - && (is_toplevel_exception - || cx.is_exhaustive_patterns_feature_on() - || cx.is_min_exhaustive_patterns_feature_on()); + let empty_arms_are_unreachable = self.validity.is_known_valid(); // Whether empty patterns can be omitted for exhaustiveness. We ignore place validity in the // toplevel exception and `exhaustive_patterns` cases for backwards compatibility. - let can_omit_empty_arms = empty_arms_are_unreachable + let can_omit_empty_arms = self.validity.is_known_valid() || is_toplevel_exception || cx.is_exhaustive_patterns_feature_on(); |