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We can traverse bindings before lower_match_tree now

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This commit is contained in:
Nadrieril 2024-06-17 19:15:03 +02:00
parent d8a38b0002
commit ea29d6ad0b
2 changed files with 101 additions and 53 deletions
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77
compiler/rustc_mir_build/src/build/matches/mod.rs
View file

@ -21,6 +21,7 @@ use rustc_span::symbol::Symbol;
use rustc_span::{BytePos, Pos, Span};
use rustc_target::abi::VariantIdx;
use tracing::{debug, instrument};
use util::visit_bindings;
// helper functions, broken out by category:
mod simplify;
@ -725,6 +726,41 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
set_match_place: bool,
) -> BlockAnd<()> {
let mut candidate = Candidate::new(initializer.clone(), irrefutable_pat, false, self);
// For matches and function arguments, the place that is being matched
// can be set when creating the variables. But the place for
// let PATTERN = ... might not even exist until we do the assignment.
// so we set it here instead.
if set_match_place {
// `try_to_place` may fail if it is unable to resolve the given `PlaceBuilder` inside a
// closure. In this case, we don't want to include a scrutinee place.
// `scrutinee_place_builder` will fail for destructured assignments. This is because a
// closure only captures the precise places that it will read and as a result a closure
// may not capture the entire tuple/struct and rather have individual places that will
// be read in the final MIR.
// Example:
// ```
// let foo = (0, 1);
// let c = || {
// let (v1, v2) = foo;
// };
// ```
if let Some(place) = initializer.try_to_place(self) {
visit_bindings(&[&mut candidate], |binding: &Binding<'_>| {
let local = self.var_local_id(binding.var_id, OutsideGuard);
if let LocalInfo::User(BindingForm::Var(VarBindingForm {
opt_match_place: Some((ref mut match_place, _)),
..
})) = **self.local_decls[local].local_info.as_mut().assert_crate_local()
{
*match_place = Some(place);
} else {
bug!("Let binding to non-user variable.")
};
});
}
}
let fake_borrow_temps = self.lower_match_tree(
block,
irrefutable_pat.span,
@ -733,47 +769,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
false,
&mut [&mut candidate],
);
// For matches and function arguments, the place that is being matched
// can be set when creating the variables. But the place for
// let PATTERN = ... might not even exist until we do the assignment.
// so we set it here instead.
if set_match_place {
let mut next = Some(&candidate);
while let Some(candidate_ref) = next.take() {
for binding in &candidate_ref.extra_data.bindings {
let local = self.var_local_id(binding.var_id, OutsideGuard);
// `try_to_place` may fail if it is unable to resolve the given
// `PlaceBuilder` inside a closure. In this case, we don't want to include
// a scrutinee place. `scrutinee_place_builder` will fail for destructured
// assignments. This is because a closure only captures the precise places
// that it will read and as a result a closure may not capture the entire
// tuple/struct and rather have individual places that will be read in the
// final MIR.
// Example:
// ```
// let foo = (0, 1);
// let c = || {
// let (v1, v2) = foo;
// };
// ```
if let Some(place) = initializer.try_to_place(self) {
let LocalInfo::User(BindingForm::Var(VarBindingForm {
opt_match_place: Some((ref mut match_place, _)),
..
})) = **self.local_decls[local].local_info.as_mut().assert_crate_local()
else {
bug!("Let binding to non-user variable.")
};
*match_place = Some(place);
}
}
// All of the subcandidates should bind the same locals, so we
// only visit the first one.
next = candidate_ref.subcandidates.get(0)
}
}
self.bind_pattern(
self.source_info(irrefutable_pat.span),
candidate,

77
compiler/rustc_mir_build/src/build/matches/util.rs
View file

@ -1,3 +1,5 @@
use std::marker::PhantomData;
use crate::build::expr::as_place::{PlaceBase, PlaceBuilder};
use crate::build::matches::{Binding, Candidate, FlatPat, MatchPair, TestCase};
use crate::build::Builder;
@ -267,18 +269,6 @@ impl<'pat, 'tcx> MatchPair<'pat, 'tcx> {
}
}
pub(super) struct FakeBorrowCollector<'a, 'b, 'tcx> {
cx: &'a mut Builder<'b, 'tcx>,
/// Base of the scrutinee place. Used to distinguish bindings inside the scrutinee place from
/// bindings inside deref patterns.
scrutinee_base: PlaceBase,
/// Store for each place the kind of borrow to take. In case of conflicts, we take the strongest
/// borrow (i.e. Deep > Shallow).
/// Invariant: for any place in `fake_borrows`, all the prefixes of this place that are
/// dereferences are also borrowed with the same of stronger borrow kind.
fake_borrows: FxIndexMap<Place<'tcx>, FakeBorrowKind>,
}
/// Determine the set of places that have to be stable across match guards.
///
/// Returns a list of places that need a fake borrow along with a local to store it.
@ -342,6 +332,18 @@ pub(super) fn collect_fake_borrows<'tcx>(
.collect()
}
pub(super) struct FakeBorrowCollector<'a, 'b, 'tcx> {
cx: &'a mut Builder<'b, 'tcx>,
/// Base of the scrutinee place. Used to distinguish bindings inside the scrutinee place from
/// bindings inside deref patterns.
scrutinee_base: PlaceBase,
/// Store for each place the kind of borrow to take. In case of conflicts, we take the strongest
/// borrow (i.e. Deep > Shallow).
/// Invariant: for any place in `fake_borrows`, all the prefixes of this place that are
/// dereferences are also borrowed with the same of stronger borrow kind.
fake_borrows: FxIndexMap<Place<'tcx>, FakeBorrowKind>,
}
impl<'a, 'b, 'tcx> FakeBorrowCollector<'a, 'b, 'tcx> {
// Fake borrow this place and its dereference prefixes.
fn fake_borrow(&mut self, place: Place<'tcx>, kind: FakeBorrowKind) {
@ -455,6 +457,57 @@ impl<'a, 'b, 'tcx> FakeBorrowCollector<'a, 'b, 'tcx> {
}
}
/// Visit all the bindings of these candidates. Because or-alternatives bind the same variables, we
/// only explore the first one of each or-pattern.
pub(super) fn visit_bindings<'tcx>(
candidates: &[&mut Candidate<'_, 'tcx>],
f: impl FnMut(&Binding<'tcx>),
) {
let mut visitor = BindingsVisitor { f, phantom: PhantomData };
for candidate in candidates.iter() {
visitor.visit_candidate(candidate);
}
}
pub(super) struct BindingsVisitor<'tcx, F> {
f: F,
phantom: PhantomData<&'tcx ()>,
}
impl<'tcx, F> BindingsVisitor<'tcx, F>
where
F: FnMut(&Binding<'tcx>),
{
fn visit_candidate(&mut self, candidate: &Candidate<'_, 'tcx>) {
for binding in &candidate.extra_data.bindings {
(self.f)(binding)
}
for match_pair in &candidate.match_pairs {
self.visit_match_pair(match_pair);
}
}
fn visit_flat_pat(&mut self, flat_pat: &FlatPat<'_, 'tcx>) {
for binding in &flat_pat.extra_data.bindings {
(self.f)(binding)
}
for match_pair in &flat_pat.match_pairs {
self.visit_match_pair(match_pair);
}
}
fn visit_match_pair(&mut self, match_pair: &MatchPair<'_, 'tcx>) {
if let TestCase::Or { pats, .. } = &match_pair.test_case {
// All the or-alternatives should bind the same locals, so we only visit the first one.
self.visit_flat_pat(&pats[0])
} else {
for subpair in &match_pair.subpairs {
self.visit_match_pair(subpair);
}
}
}
}
#[must_use]
pub(crate) fn ref_pat_borrow_kind(ref_mutability: Mutability) -> BorrowKind {
match ref_mutability {