Rollup merge of #99156 - lcnr:omoe-wa, r=wesleywiser

`codegen_fulfill_obligation` expect erased regions

it's a query, so by erasing regions before calling it, we get better caching.
This doesn't actually change anything as its already the status quo.

compiler/rustc_infer/src/infer/mod.rs

@@ -8,7 +8,7 @@ pub use self::ValuePairs::*;
 use self::opaque_types::OpaqueTypeStorage;
 pub(crate) use self::undo_log::{InferCtxtUndoLogs, Snapshot, UndoLog};
 
-use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine};
+use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine, TraitEngineExt};
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::sync::Lrc;
@@ -645,9 +645,7 @@ impl<'tcx, T> InferOk<'tcx, T> {
         fulfill_cx: &mut dyn TraitEngine<'tcx>,
     ) -> T {
         let InferOk { value, obligations } = self;
-        for obligation in obligations {
-            fulfill_cx.register_predicate_obligation(infcx, obligation);
-        }
+        fulfill_cx.register_predicate_obligations(infcx, obligations);
         value
     }
 }

compiler/rustc_trait_selection/src/traits/codegen.rs

@@ -23,8 +23,6 @@ pub fn codegen_fulfill_obligation<'tcx>(
     tcx: TyCtxt<'tcx>,
     (param_env, trait_ref): (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>),
 ) -> Result<&'tcx ImplSource<'tcx, ()>, CodegenObligationError> {
-    // Remove any references to regions; this helps improve caching.
-    let trait_ref = tcx.erase_regions(trait_ref);
     // We expect the input to be fully normalized.
     debug_assert_eq!(trait_ref, tcx.normalize_erasing_regions(param_env, trait_ref));