Rollup merge of #72754 - lcnr:predicate-fold, r=nikomatsakis

Dylan-DPC · web-flow · commit f14c1d43197d · 2020-06-03T22:07:59.000+02:00
remove trivial `mk_predicate`s r? @nikomatsakis
diff --git a/src/librustc_middle/ty/structural_impls.rs b/src/librustc_middle/ty/structural_impls.rs
@@ -987,7 +987,8 @@ impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
 
 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
-        folder.tcx().mk_predicate(ty::PredicateKind::super_fold_with(self.kind, folder))
+        let new = ty::PredicateKind::super_fold_with(self.kind, folder);
+        if new != *self.kind { folder.tcx().mk_predicate(new) } else { *self }
     }
 
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {

Original file line number	Diff line number	Diff line change
`@@ -987,7 +987,8 @@ impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {`
`987`	`987`
`988`	`988`	`impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {`
`989`	`989`	`fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {`
`990`		`- folder.tcx().mk_predicate(ty::PredicateKind::super_fold_with(self.kind, folder))`
	`990`	`+ let new = ty::PredicateKind::super_fold_with(self.kind, folder);`
	`991`	`+ if new != self.kind { folder.tcx().mk_predicate(new) } else { self }`
`991`	`992`	`}`
`992`	`993`
`993`	`994`	`fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {`