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Remove confusing use_polonius flag and do less cloning

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The `use_polonius` flag is both redundant and confusing since every
function it's propagated to also checks if `all_facts` is `Some`,
the true test of whether to generate Polonius facts for Polonius
or for external consumers. This PR makes that path clearer by
simply doing away with the argument and handling the logic in
precisely two places: where facts are populated (check for `Some`),
and where `all_facts` are initialised. It also delays some statements
until after that check to avoid the miniscule performance penalty
of executing them when Polonius is disabled.

This also addresses @lqd's concern in #125652 by reducing
the size of what is cloned out of Polonius facts to just the
facts being added, as opposed to the entire vector of potential
inputs, and added descriptive comments.

*Reviewer note*: the comments in [add_extra_drop_facts](85f90a4612/compiler/rustc_borrowck/src/type_check/liveness/trace.rs (L219)) should be inspected by a reviewer,
in particular the one on L#259 in this PR, which should be trivial
for someone with the right background knowledge.

I also included some minor lints I found on the way there that I
couldn't help myself from addressing.
This commit is contained in:
Amanda Stjerna 2024-06-05 10:57:27 +02:00
parent 85f90a4612
commit 7b5b7a7010
13 changed files with 55 additions and 49 deletions
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6
compiler/rustc_borrowck/src/dataflow.rs
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@ -43,9 +43,9 @@ impl<'mir, 'tcx> ResultsVisitable<'tcx> for BorrowckResults<'mir, 'tcx> {
}
fn reset_to_block_entry(&self, state: &mut Self::FlowState, block: BasicBlock) {
state.borrows.clone_from(&self.borrows.entry_set_for_block(block));
state.uninits.clone_from(&self.uninits.entry_set_for_block(block));
state.ever_inits.clone_from(&self.ever_inits.entry_set_for_block(block));
state.borrows.clone_from(self.borrows.entry_set_for_block(block));
state.uninits.clone_from(self.uninits.entry_set_for_block(block));
state.ever_inits.clone_from(self.ever_inits.entry_set_for_block(block));
}
fn reconstruct_before_statement_effect(