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Remove lub_empty from lexical region resolve #115224

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merged 3 commits into from
Aug 26, 2023
Merged

Remove lub_empty from lexical region resolve #115224

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78da436
Remove lub_empty from lexical region resolve
spastorino Aug 25, 2023
e2efb6a
Check that universe can name other universe instead of equality
spastorino Aug 25, 2023
b92840a
Merge if and match expressions that don't make sense to have separated
spastorino Aug 26, 2023
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65 changes: 19 additions & 46 deletions compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,6 @@ use rustc_data_structures::graph::implementation::{
use rustc_data_structures::intern::Interned;
use rustc_index::{IndexSlice, IndexVec};
use rustc_middle::ty::fold::TypeFoldable;
use rustc_middle::ty::PlaceholderRegion;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::ty::{ReEarlyBound, ReErased, ReError, ReFree, ReStatic};
use rustc_middle::ty::{ReLateBound, RePlaceholder, ReVar};
Expand Down Expand Up @@ -173,38 +172,6 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
}
}

/// Gets the LUb of a given region and the empty region
fn lub_empty(&self, a_region: Region<'tcx>) -> Result<Region<'tcx>, PlaceholderRegion> {
match *a_region {
ReLateBound(..) | ReErased => {
bug!("cannot relate region: {:?}", a_region);
}

ReVar(v_id) => {
span_bug!(
self.var_infos[v_id].origin.span(),
"lub invoked with non-concrete regions: {:?}",
a_region,
);
}

ReStatic => {
// nothing lives longer than `'static`
Ok(self.tcx().lifetimes.re_static)
}

ReError(_) => Ok(a_region),

ReEarlyBound(_) | ReFree(_) => {
// All empty regions are less than early-bound, free,
// and scope regions.
Ok(a_region)
}

RePlaceholder(placeholder) => Err(placeholder),
}
}

fn expansion(&self, var_values: &mut LexicalRegionResolutions<'tcx>) {
// In the first pass, we expand region vids according to constraints we
// have previously found. In the second pass, we loop through the region
Expand Down Expand Up @@ -247,15 +214,17 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
true
}
VarValue::Value(cur_region) => {
let lub = match self.lub_empty(cur_region) {
Ok(r) => r,
let lub = match *cur_region {
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// If the empty and placeholder regions are in the same universe,
// then the LUB is the Placeholder region (which is the cur_region).
// If they are not in the same universe, the LUB is the Static lifetime.
Err(placeholder) if a_universe == placeholder.universe => {
cur_region
RePlaceholder(placeholder)
if a_universe != placeholder.universe =>
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{
self.tcx().lifetimes.re_static
}
Err(_) => self.tcx().lifetimes.re_static,

_ => cur_region,
};

if lub == cur_region {
Expand Down Expand Up @@ -341,15 +310,19 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {

match *b_data {
VarValue::Empty(empty_ui) => {
let lub = match self.lub_empty(a_region) {
Ok(r) => r,
// If this empty region is from a universe that can
// name the placeholder, then the placeholder is
// larger; otherwise, the only ancestor is `'static`.
Err(placeholder) if empty_ui.can_name(placeholder.universe) => {
ty::Region::new_placeholder(self.tcx(), placeholder)
let lub = match *a_region {
RePlaceholder(placeholder) => {
// If this empty region is from a universe that can
// name the placeholder, then the placeholder is
// larger; otherwise, the only ancestor is `'static`.
if empty_ui.can_name(placeholder.universe) {
ty::Region::new_placeholder(self.tcx(), placeholder)
} else {
self.tcx().lifetimes.re_static
}
}
Err(_) => self.tcx().lifetimes.re_static,

_ => a_region,
};

debug!("Expanding value of {:?} from empty lifetime to {:?}", b_vid, lub);
Expand Down