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A drive-by rewrite of give_region_a_name()

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This rewrite makes the cache-updating nature of the function slightly clearer, using the Entry API into the hash table for region names to capture the update-insert nature of the method. May be marginally more efficient since it only runtime-borrows the map once, but in this context the performance impact is almost certainly completely negligible.
This commit is contained in:
Amanda Stjerna 2024-02-06 13:07:51 +01:00
parent 94df917a74
commit ad3d04c55e
1 changed files with 22 additions and 18 deletions
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40
compiler/rustc_borrowck/src/diagnostics/region_name.rs
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@ -1,6 +1,7 @@
use std::fmt::{self, Display};
use std::iter;
use rustc_data_structures::fx::IndexEntry;
use rustc_errors::Diagnostic;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
@ -247,25 +248,28 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
assert!(self.regioncx.universal_regions().is_universal_region(fr));
if let Some(value) = self.region_names.try_borrow_mut().unwrap().get(&fr) {
return Some(value.clone());
match self.region_names.borrow_mut().entry(fr) {
IndexEntry::Occupied(precomputed_name) => Some(precomputed_name.get().clone()),
IndexEntry::Vacant(slot) => {
let new_name = self
.give_name_from_error_region(fr)
.or_else(|| self.give_name_if_anonymous_region_appears_in_arguments(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_upvars(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_output(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_yield_ty(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_impl_signature(fr))
.or_else(|| {
self.give_name_if_anonymous_region_appears_in_arg_position_impl_trait(fr)
});
if let Some(new_name) = &new_name {
slot.insert(new_name.clone());
}
debug!("give_region_a_name: gave name {:?}", new_name);
new_name
}
}
let value = self
.give_name_from_error_region(fr)
.or_else(|| self.give_name_if_anonymous_region_appears_in_arguments(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_upvars(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_output(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_yield_ty(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_impl_signature(fr))
.or_else(|| self.give_name_if_anonymous_region_appears_in_arg_position_impl_trait(fr));
if let Some(value) = &value {
self.region_names.try_borrow_mut().unwrap().insert(fr, value.clone());
}
debug!("give_region_a_name: gave name {:?}", value);
value
}
/// Checks for the case where `fr` maps to something that the