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Track is_top_level via PlaceInfo

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This commit is contained in:
Nadrieril 2024-01-31 02:46:10 +01:00
parent 411967c078
commit 6cac1c459e
1 changed files with 14 additions and 10 deletions
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24
compiler/rustc_pattern_analysis/src/usefulness.rs
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@ -828,6 +828,8 @@ struct PlaceInfo<Cx: TypeCx> {
ty: Cx::Ty,
/// Whether the place is known to contain valid data.
validity: ValidityConstraint,
/// Whether the place is the scrutinee itself or a subplace of it.
is_scrutinee: bool,
}
impl<Cx: TypeCx> PlaceInfo<Cx> {
@ -838,13 +840,17 @@ impl<Cx: TypeCx> PlaceInfo<Cx> {
) -> impl Iterator<Item = Self> + ExactSizeIterator + Captures<'a> {
let ctor_sub_tys = cx.ctor_sub_tys(ctor, &self.ty);
let ctor_sub_validity = self.validity.specialize(ctor);
ctor_sub_tys.map(move |ty| PlaceInfo { ty, validity: ctor_sub_validity })
ctor_sub_tys.map(move |ty| PlaceInfo {
ty,
validity: ctor_sub_validity,
is_scrutinee: false,
})
}
}
impl<Cx: TypeCx> Clone for PlaceInfo<Cx> {
fn clone(&self) -> Self {
Self { ty: self.ty.clone(), validity: self.validity }
Self { ty: self.ty.clone(), validity: self.validity, is_scrutinee: self.is_scrutinee }
}
}
@ -1051,7 +1057,7 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
scrut_ty: Cx::Ty,
scrut_validity: ValidityConstraint,
) -> Self {
let place_info = PlaceInfo { ty: scrut_ty, validity: scrut_validity };
let place_info = PlaceInfo { ty: scrut_ty, validity: scrut_validity, is_scrutinee: true };
let mut matrix = Matrix {
rows: Vec::with_capacity(arms.len()),
place_info: smallvec![place_info],
@ -1446,11 +1452,10 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
/// - unspecialization, where we lift the results from the previous step into results for this step
/// (using `apply_constructor` and by updating `row.useful` for each parent row).
/// This is all explained at the top of the file.
#[instrument(level = "debug", skip(mcx, is_top_level), ret)]
#[instrument(level = "debug", skip(mcx), ret)]
fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
mcx: UsefulnessCtxt<'a, Cx>,
matrix: &mut Matrix<'p, Cx>,
is_top_level: bool,
) -> Result<WitnessMatrix<Cx>, Cx::Error> {
debug_assert!(matrix.rows().all(|r| r.len() == matrix.column_count()));
@ -1488,7 +1493,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
// We treat match scrutinees of type `!` or `EmptyEnum` differently.
let is_toplevel_exception =
is_top_level && matches!(ctors_for_ty, ConstructorSet::NoConstructors);
place.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 = place.validity.is_known_valid()
@ -1517,7 +1522,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
// Decide what constructors to report.
let is_integers = matches!(ctors_for_ty, ConstructorSet::Integers { .. });
let always_report_all = is_top_level && !is_integers;
let always_report_all = place.is_scrutinee && !is_integers;
// Whether we should report "Enum::A and Enum::C are missing" or "_ is missing".
let report_individual_missing_ctors = always_report_all || !all_missing;
// Which constructors are considered missing. We ensure that `!missing_ctors.is_empty() =>
@ -1538,7 +1543,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
let ctor_is_relevant = matches!(ctor, Constructor::Missing) || missing_ctors.is_empty();
let mut spec_matrix = matrix.specialize_constructor(pcx, &ctor, ctor_is_relevant)?;
let mut witnesses = ensure_sufficient_stack(|| {
compute_exhaustiveness_and_usefulness(mcx, &mut spec_matrix, false)
compute_exhaustiveness_and_usefulness(mcx, &mut spec_matrix)
})?;
// Transform witnesses for `spec_matrix` into witnesses for `matrix`.
@ -1613,8 +1618,7 @@ pub fn compute_match_usefulness<'p, Cx: TypeCx>(
) -> Result<UsefulnessReport<'p, Cx>, Cx::Error> {
let cx = UsefulnessCtxt { tycx };
let mut matrix = Matrix::new(arms, scrut_ty, scrut_validity);
let non_exhaustiveness_witnesses =
compute_exhaustiveness_and_usefulness(cx, &mut matrix, true)?;
let non_exhaustiveness_witnesses = compute_exhaustiveness_and_usefulness(cx, &mut matrix)?;
let non_exhaustiveness_witnesses: Vec<_> = non_exhaustiveness_witnesses.single_column();
let arm_usefulness: Vec<_> = arms