bjoernager/rust
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Make all the empty pattern decisions in usefulness

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This commit is contained in:
Nadrieril 2024-01-10 22:23:21 +01:00
parent bf913ad0ae
commit edb27a306a
3 changed files with 19 additions and 20 deletions
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18
compiler/rustc_pattern_analysis/src/usefulness.rs
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@ -737,15 +737,13 @@ pub(crate) struct PlaceCtxt<'a, Cx: TypeCx> {
pub(crate) mcx: MatchCtxt<'a, Cx>,
/// Type of the place under investigation.
pub(crate) ty: Cx::Ty,
/// Whether the place is the original scrutinee place, as opposed to a subplace of it.
pub(crate) is_scrutinee: bool,
}
impl<'a, Cx: TypeCx> PlaceCtxt<'a, Cx> {
/// A `PlaceCtxt` when code other than `is_useful` needs one.
#[cfg_attr(not(feature = "rustc"), allow(dead_code))]
pub(crate) fn new_dummy(mcx: MatchCtxt<'a, Cx>, ty: Cx::Ty) -> Self {
PlaceCtxt { mcx, ty, is_scrutinee: false }
PlaceCtxt { mcx, ty }
}
pub(crate) fn ctor_arity(&self, ctor: &Constructor<Cx>) -> usize {
@ -1442,7 +1440,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
};
debug!("ty: {ty:?}");
let pcx = &PlaceCtxt { mcx, ty, is_scrutinee: is_top_level };
let pcx = &PlaceCtxt { mcx, ty };
// Whether the place/column we are inspecting is known to contain valid data.
let place_validity = matrix.place_validity[0];
@ -1451,7 +1449,17 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
let ctors = matrix.heads().map(|p| p.ctor());
let ctors_for_ty = pcx.ctors_for_ty()?;
let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. }); // For diagnostics.
let split_set = ctors_for_ty.split(pcx, ctors);
let mut split_set = ctors_for_ty.split(ctors);
// We have now grouped all the constructors into 3 buckets: present, missing, missing_empty.
// In the absence of the `exhaustive_patterns` feature however, we don't count nested empty
// types as empty. Only non-nested `!` or `enum Foo {}` are considered empty.
if !pcx.mcx.tycx.is_exhaustive_patterns_feature_on()
&& !(is_top_level && matches!(ctors_for_ty, ConstructorSet::NoConstructors))
{
// Treat all missing constructors as nonempty.
// This clears `missing_empty`.
split_set.missing.append(&mut split_set.missing_empty);
}
let all_missing = split_set.present.is_empty();
// Build the set of constructors we will specialize with. It must cover the whole type.