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Auto merge of #135615 - matthiaskrgr:rollup-ra7vftt, r=matthiaskrgr
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Rollup of 6 pull requests

Successful merges:

 - #131806 (Treat other items as functions for the purpose of type-based search)
 - #134980 (Location-sensitive polonius prototype: endgame)
 - #135558 (Detect if-else chains with a missing final else in type errors)
 - #135594 (fix error for when results in a rustdoc-js test are in the wrong order)
 - #135601 (Fix suggestion to convert dereference of raw pointer to ref)
 - #135604 (Expand docs for `E0207` with additional example)

r? `@ghost`
`@rustbot` modify labels: rollup
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bors committed Jan 17, 2025
2 parents 0c2c096 + 1360e76 commit 73c0ae6
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Showing 24 changed files with 596 additions and 188 deletions.
101 changes: 45 additions & 56 deletions compiler/rustc_borrowck/src/dataflow.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -187,19 +187,28 @@ struct OutOfScopePrecomputer<'a, 'tcx> {
borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
}

impl<'a, 'tcx> OutOfScopePrecomputer<'a, 'tcx> {
fn new(body: &'a Body<'tcx>, regioncx: &'a RegionInferenceContext<'tcx>) -> Self {
OutOfScopePrecomputer {
impl<'tcx> OutOfScopePrecomputer<'_, 'tcx> {
fn compute(
body: &Body<'tcx>,
regioncx: &RegionInferenceContext<'tcx>,
borrow_set: &BorrowSet<'tcx>,
) -> FxIndexMap<Location, Vec<BorrowIndex>> {
let mut prec = OutOfScopePrecomputer {
visited: DenseBitSet::new_empty(body.basic_blocks.len()),
visit_stack: vec![],
body,
regioncx,
borrows_out_of_scope_at_location: FxIndexMap::default(),
};
for (borrow_index, borrow_data) in borrow_set.iter_enumerated() {
let borrow_region = borrow_data.region;
let location = borrow_data.reserve_location;
prec.precompute_borrows_out_of_scope(borrow_index, borrow_region, location);
}

prec.borrows_out_of_scope_at_location
}
}

impl<'tcx> OutOfScopePrecomputer<'_, 'tcx> {
fn precompute_borrows_out_of_scope(
&mut self,
borrow_index: BorrowIndex,
Expand Down Expand Up @@ -280,15 +289,7 @@ pub fn calculate_borrows_out_of_scope_at_location<'tcx>(
regioncx: &RegionInferenceContext<'tcx>,
borrow_set: &BorrowSet<'tcx>,
) -> FxIndexMap<Location, Vec<BorrowIndex>> {
let mut prec = OutOfScopePrecomputer::new(body, regioncx);
for (borrow_index, borrow_data) in borrow_set.iter_enumerated() {
let borrow_region = borrow_data.region;
let location = borrow_data.reserve_location;

prec.precompute_borrows_out_of_scope(borrow_index, borrow_region, location);
}

prec.borrows_out_of_scope_at_location
OutOfScopePrecomputer::compute(body, regioncx, borrow_set)
}

struct PoloniusOutOfScopePrecomputer<'a, 'tcx> {
Expand All @@ -300,19 +301,30 @@ struct PoloniusOutOfScopePrecomputer<'a, 'tcx> {
loans_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
}

impl<'a, 'tcx> PoloniusOutOfScopePrecomputer<'a, 'tcx> {
fn new(body: &'a Body<'tcx>, regioncx: &'a RegionInferenceContext<'tcx>) -> Self {
Self {
impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
fn compute(
body: &Body<'tcx>,
regioncx: &RegionInferenceContext<'tcx>,
borrow_set: &BorrowSet<'tcx>,
) -> FxIndexMap<Location, Vec<BorrowIndex>> {
// The in-tree polonius analysis computes loans going out of scope using the
// set-of-loans model.
let mut prec = PoloniusOutOfScopePrecomputer {
visited: DenseBitSet::new_empty(body.basic_blocks.len()),
visit_stack: vec![],
body,
regioncx,
loans_out_of_scope_at_location: FxIndexMap::default(),
};
for (loan_idx, loan_data) in borrow_set.iter_enumerated() {
let issuing_region = loan_data.region;
let loan_issued_at = loan_data.reserve_location;
prec.precompute_loans_out_of_scope(loan_idx, issuing_region, loan_issued_at);
}

prec.loans_out_of_scope_at_location
}
}

impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
/// Loans are in scope while they are live: whether they are contained within any live region.
/// In the location-insensitive analysis, a loan will be contained in a region if the issuing
/// region can reach it in the subset graph. So this is a reachability problem.
Expand All @@ -325,10 +337,17 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
let sccs = self.regioncx.constraint_sccs();
let universal_regions = self.regioncx.universal_regions();

// The loop below was useful for the location-insensitive analysis but shouldn't be
// impactful in the location-sensitive case. It seems that it does, however, as without it a
// handful of tests fail. That likely means some liveness or outlives data related to choice
// regions is missing
// FIXME: investigate the impact of loans traversing applied member constraints and why some
// tests fail otherwise.
//
// We first handle the cases where the loan doesn't go out of scope, depending on the
// issuing region's successors.
for successor in graph::depth_first_search(&self.regioncx.region_graph(), issuing_region) {
// 1. Via applied member constraints
// Via applied member constraints
//
// The issuing region can flow into the choice regions, and they are either:
// - placeholders or free regions themselves,
Expand All @@ -346,14 +365,6 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
return;
}
}

// 2. Via regions that are live at all points: placeholders and free regions.
//
// If the issuing region outlives such a region, its loan escapes the function and
// cannot go out of scope. We can early return.
if self.regioncx.is_region_live_at_all_points(successor) {
return;
}
}

let first_block = loan_issued_at.block;
Expand Down Expand Up @@ -461,34 +472,12 @@ impl<'a, 'tcx> Borrows<'a, 'tcx> {
regioncx: &RegionInferenceContext<'tcx>,
borrow_set: &'a BorrowSet<'tcx>,
) -> Self {
let mut borrows_out_of_scope_at_location =
calculate_borrows_out_of_scope_at_location(body, regioncx, borrow_set);

// The in-tree polonius analysis computes loans going out of scope using the set-of-loans
// model, and makes sure they're identical to the existing computation of the set-of-points
// model.
if tcx.sess.opts.unstable_opts.polonius.is_next_enabled() {
let mut polonius_prec = PoloniusOutOfScopePrecomputer::new(body, regioncx);
for (loan_idx, loan_data) in borrow_set.iter_enumerated() {
let issuing_region = loan_data.region;
let loan_issued_at = loan_data.reserve_location;

polonius_prec.precompute_loans_out_of_scope(
loan_idx,
issuing_region,
loan_issued_at,
);
}

assert_eq!(
borrows_out_of_scope_at_location, polonius_prec.loans_out_of_scope_at_location,
"polonius loan scopes differ from NLL borrow scopes, for body {:?}",
body.span,
);

borrows_out_of_scope_at_location = polonius_prec.loans_out_of_scope_at_location;
}

let borrows_out_of_scope_at_location =
if !tcx.sess.opts.unstable_opts.polonius.is_next_enabled() {
calculate_borrows_out_of_scope_at_location(body, regioncx, borrow_set)
} else {
PoloniusOutOfScopePrecomputer::compute(body, regioncx, borrow_set)
};
Borrows { tcx, body, borrow_set, borrows_out_of_scope_at_location }
}

Expand Down
10 changes: 5 additions & 5 deletions compiler/rustc_borrowck/src/nll.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
constraints,
universal_region_relations,
opaque_type_values,
mut polonius_context,
polonius_context,
} = type_check::type_check(
infcx,
body,
Expand Down Expand Up @@ -142,10 +142,10 @@ pub(crate) fn compute_regions<'a, 'tcx>(
location_map,
);

// If requested for `-Zpolonius=next`, convert NLL constraints to localized outlives
// constraints.
let localized_outlives_constraints = polonius_context.as_mut().map(|polonius_context| {
polonius_context.create_localized_constraints(infcx.tcx, &regioncx, body)
// If requested for `-Zpolonius=next`, convert NLL constraints to localized outlives constraints
// and use them to compute loan liveness.
let localized_outlives_constraints = polonius_context.as_ref().map(|polonius_context| {
polonius_context.compute_loan_liveness(infcx.tcx, &mut regioncx, body, borrow_set)
});

// If requested: dump NLL facts, and run legacy polonius analysis.
Expand Down
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