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Merge pull request #18645 from Veykril/push-yruoyrvrsntw
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fix: Non-exhaustive structs may be empty
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Veykril authored Dec 9, 2024
2 parents d824871 + 55a7ee8 commit 067b4a3
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Showing 3 changed files with 21 additions and 12 deletions.
6 changes: 1 addition & 5 deletions crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs
Original file line number Diff line number Diff line change
Expand Up @@ -383,9 +383,6 @@ impl<'db> PatCx for MatchCheckCtx<'db> {
} else {
let variant = Self::variant_id_for_adt(self.db, ctor, adt).unwrap();

// Whether we must not match the fields of this variant exhaustively.
let is_non_exhaustive =
LazyCell::new(|| self.is_foreign_non_exhaustive(adt));
let visibilities = LazyCell::new(|| self.db.field_visibilities(variant));

self.list_variant_fields(ty, variant)
Expand All @@ -396,8 +393,7 @@ impl<'db> PatCx for MatchCheckCtx<'db> {
.is_visible_from(self.db.upcast(), self.module)
};
let is_uninhabited = self.is_uninhabited(&ty);
let private_uninhabited =
is_uninhabited && (!is_visible() || *is_non_exhaustive);
let private_uninhabited = is_uninhabited && !is_visible();
(ty, PrivateUninhabitedField(private_uninhabited))
})
.collect()
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8 changes: 1 addition & 7 deletions crates/hir-ty/src/inhabitedness.rs
Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,7 @@ use chalk_ir::{
visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor},
DebruijnIndex,
};
use hir_def::{visibility::Visibility, AdtId, EnumVariantId, HasModule, ModuleId, VariantId};
use intern::sym;
use hir_def::{visibility::Visibility, AdtId, EnumVariantId, ModuleId, VariantId};
use rustc_hash::FxHashSet;

use crate::{
Expand Down Expand Up @@ -118,11 +117,6 @@ impl UninhabitedFrom<'_> {
variant: VariantId,
subst: &Substitution,
) -> ControlFlow<VisiblyUninhabited> {
let is_local = variant.krate(self.db.upcast()) == self.target_mod.krate();
if !is_local && self.db.attrs(variant.into()).by_key(&sym::non_exhaustive).exists() {
return CONTINUE_OPAQUELY_INHABITED;
}

let variant_data = self.db.variant_data(variant);
let fields = variant_data.fields();
if fields.is_empty() {
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19 changes: 19 additions & 0 deletions crates/ide-diagnostics/src/handlers/missing_match_arms.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1114,6 +1114,25 @@ fn test(x: Option<lib::PrivatelyUninhabited>) {
}
}

#[test]
fn non_exhaustive_may_be_empty() {
check_diagnostics_no_bails(
r"
//- /main.rs crate:main deps:dep
// In a different crate
fn empty_match_on_empty_struct<T>(x: dep::UninhabitedStruct) -> T {
match x {}
}
//- /dep.rs crate:dep
#[non_exhaustive]
pub struct UninhabitedStruct {
pub never: !,
// other fields
}
",
);
}

mod false_negatives {
//! The implementation of match checking here is a work in progress. As we roll this out, we
//! prefer false negatives to false positives (ideally there would be no false positives). This
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