bjoernager/rust
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Clarifying comment

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This commit is contained in:
Michael Goulet 2024-03-27 16:02:13 -04:00
parent a9e262a32d
commit da2b714ba1
1 changed files with 9 additions and 3 deletions
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12
compiler/rustc_hir_analysis/src/check/wfcheck.rs
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@ -2089,13 +2089,19 @@ fn lint_redundant_lifetimes<'tcx>(
let mut shadowed = FxHashSet::default(); let mut shadowed = FxHashSet::default();
for (idx, &candidate) in lifetimes.iter().enumerate() { for (idx, &candidate) in lifetimes.iter().enumerate() {
// Don't suggest removing a lifetime twice. // Don't suggest removing a lifetime twice. We only need to check this
// here and not up in the `victim` loop because equality is transitive,
// so if A = C and B = C, then A must = B, so it'll be shadowed too in
// A's victim loop.
if shadowed.contains(&candidate) { if shadowed.contains(&candidate) {
continue; continue;
} }
for &victim in &lifetimes[(idx + 1)..] { for &victim in &lifetimes[(idx + 1)..] {
// We only care about lifetimes that are "real", i.e. that have a def-id. // We should only have late-bound lifetimes of the `BrNamed` variety,
// since we get these signatures straight from `hir_lowering`. And any
// other regions (ReError/ReStatic/etc.) shouldn't matter, since we
// can't really suggest to remove them.
let (ty::ReEarlyParam(ty::EarlyParamRegion { def_id, .. }) let (ty::ReEarlyParam(ty::EarlyParamRegion { def_id, .. })
| ty::ReLateParam(ty::LateParamRegion { | ty::ReLateParam(ty::LateParamRegion {
bound_region: ty::BoundRegionKind::BrNamed(def_id, _), bound_region: ty::BoundRegionKind::BrNamed(def_id, _),
@ -2113,7 +2119,7 @@ fn lint_redundant_lifetimes<'tcx>(
continue; continue;
} }
// If there are no lifetime errors, then we have proven that `'candidate = 'victim`! // If `candidate <: victim` and `victim <: candidate`, then they're equal.
if outlives_env.free_region_map().sub_free_regions(tcx, candidate, victim) if outlives_env.free_region_map().sub_free_regions(tcx, candidate, victim)
&& outlives_env.free_region_map().sub_free_regions(tcx, victim, candidate) && outlives_env.free_region_map().sub_free_regions(tcx, victim, candidate)
{ {