Auto merge of #126023 - amandasystems:you-dropped-this-again, r=nikom… · rust-lang/rust@d49994b (original) (raw)
`@@ -217,35 +217,52 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
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`/// Add facts for all locals with free regions, since regions may outlive
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`/// the function body only at certain nodes in the CFG.
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`fn add_extra_drop_facts(&mut self, relevant_live_locals: &[Local]) -> Option<()> {
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let drop_used = self
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.cx
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.typeck
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.borrowck_context
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.all_facts
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.as_ref()
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.map(|facts| facts.var_dropped_at.clone())?;
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// This collect is more necessary than immediately apparent
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// because these facts go into add_drop_live_facts_for(),
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// which also writes to all_facts, and so this is genuinely
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// a simulatneous overlapping mutable borrow.
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// FIXME for future hackers: investigate whether this is
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// actually necessary; these facts come from Polonius
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// and probably maybe plausibly does not need to go back in.
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// It may be necessary to just pick out the parts of
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// add_drop_live_facts_for() that make sense.
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let facts_to_add: Vec<_> = {
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let drop_used = &self.cx.typeck.borrowck_context.all_facts.as_ref()?.var_dropped_at;
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let relevant_live_locals: FxIndexSet<_> =
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relevant_live_locals.iter().copied().collect();
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drop_used
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.iter()
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.filter_map(|(local, location_index)| {
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let local_ty = self.cx.body.local_decls[*local].ty;
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if relevant_live_locals.contains(local) || !local_ty.has_free_regions() {
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return None;
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}
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let relevant_live_locals: FxIndexSet<_> = relevant_live_locals.iter().copied().collect();
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``
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let locations = IntervalSet::new(self.cx.elements.num_points());
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for (local, location_index) in drop_used {
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if !relevant_live_locals.contains(&local) {
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let local_ty = self.cx.body.local_decls[local].ty;
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if local_ty.has_free_regions() {
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`let location = match self
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`.cx
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`.typeck
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`.borrowck_context
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`.location_table
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.to_location(location_index)
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.to_location(*location_index)
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`{
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`RichLocation::Start(l) => l,
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`RichLocation::Mid(l) => l,
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`};
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self.cx.add_drop_live_facts_for(local, local_ty, &[location], &locations);
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}
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}
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Some((*local, local_ty, location))
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})
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.collect()
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};
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// FIXME: these locations seem to have a special meaning (e.g. everywhere, at the end, ...), but I don't know which one. Please help me rename it to something descriptive!
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// Also, if this IntervalSet is used in many places, it maybe should have a newtype'd
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// name with a description of what it means for future mortals passing by.
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let locations = IntervalSet::new(self.cx.elements.num_points());
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for (local, local_ty, location) in facts_to_add {
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self.cx.add_drop_live_facts_for(local, local_ty, &[location], &locations);
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`}
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`Some(())
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`}
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