bjoernager/rust
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pick off some easy cases for LUB/GLB in regions

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the goal here is to minimize creating variables
This commit is contained in:
Niko Matsakis 2016-03-17 05:22:53 -04:00
parent ad6ca084e7
commit cdaee4aba7
1 changed files with 13 additions and 12 deletions
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17
src/librustc/middle/infer/region_inference/mod.rs
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@ -530,18 +530,16 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
assert!(self.values_are_none()); assert!(self.values_are_none());
debug!("RegionVarBindings: lub_regions({:?}, {:?})", a, b); debug!("RegionVarBindings: lub_regions({:?}, {:?})", a, b);
match (a, b) { if a == ty::ReStatic || b == ty::ReStatic {
(ReStatic, _) | (_, ReStatic) => {
ReStatic // nothing lives longer than static ReStatic // nothing lives longer than static
} } else if a == b {
a // LUB(a,a) = a
_ => { } else {
self.combine_vars(Lub, a, b, origin.clone(), |this, old_r, new_r| { self.combine_vars(Lub, a, b, origin.clone(), |this, old_r, new_r| {
this.make_subregion(origin.clone(), old_r, new_r) this.make_subregion(origin.clone(), old_r, new_r)
}) })
} }
} }
}
pub fn glb_regions(&self, origin: SubregionOrigin<'tcx>, a: Region, b: Region) -> Region { pub fn glb_regions(&self, origin: SubregionOrigin<'tcx>, a: Region, b: Region) -> Region {
// cannot add constraints once regions are resolved // cannot add constraints once regions are resolved
@ -550,8 +548,11 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
debug!("RegionVarBindings: glb_regions({:?}, {:?})", a, b); debug!("RegionVarBindings: glb_regions({:?}, {:?})", a, b);
match (a, b) { match (a, b) {
(ReStatic, r) | (r, ReStatic) => { (ReStatic, r) | (r, ReStatic) => {
// static lives longer than everything else r // static lives longer than everything else
r }
_ if a == b => {
a // GLB(a,a) = a
} }
_ => { _ => {