Rollup merge of #127439 - compiler-errors:uplift-elaborate, r=lcnr

Uplift elaboration into `rustc_type_ir`

Allows us to deduplicate and consolidate elaboration (including these stupid elaboration duplicate fns i added for pretty printing like 3 years ago) so I'm pretty hyped about this change :3

r? lcnr

Author: jieyouxu

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -478,7 +478,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
                             param_env,
                             item_def_id,
                             tcx.explicit_item_bounds(item_def_id)
-                                .instantiate_identity_iter_copied()
+                                .iter_identity_copied()
                                 .collect::<Vec<_>>(),
                             &FxIndexSet::default(),
                             gat_def_id,
@@ -1205,17 +1205,16 @@ fn check_associated_type_bounds(wfcx: &WfCheckingCtxt<'_, '_>, item: ty::AssocIt
     let bounds = wfcx.tcx().explicit_item_bounds(item.def_id);
 
     debug!("check_associated_type_bounds: bounds={:?}", bounds);
-    let wf_obligations =
-        bounds.instantiate_identity_iter_copied().flat_map(|(bound, bound_span)| {
-            let normalized_bound = wfcx.normalize(span, None, bound);
-            traits::wf::clause_obligations(
-                wfcx.infcx,
-                wfcx.param_env,
-                wfcx.body_def_id,
-                normalized_bound,
-                bound_span,
-            )
-        });
+    let wf_obligations = bounds.iter_identity_copied().flat_map(|(bound, bound_span)| {
+        let normalized_bound = wfcx.normalize(span, None, bound);
+        traits::wf::clause_obligations(
+            wfcx.infcx,
+            wfcx.param_env,
+            wfcx.body_def_id,
+            normalized_bound,
+            bound_span,
+        )
+    });
 
     wfcx.register_obligations(wf_obligations);
 }

compiler/rustc_hir_typeck/src/coercion.rs

@@ -1752,10 +1752,8 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
             fcx.probe(|_| {
                 let ocx = ObligationCtxt::new(fcx);
                 ocx.register_obligations(
-                    fcx.tcx
-                        .item_super_predicates(rpit_def_id)
-                        .instantiate_identity_iter()
-                        .filter_map(|clause| {
+                    fcx.tcx.item_super_predicates(rpit_def_id).iter_identity().filter_map(
+                        |clause| {
                             let predicate = clause
                                 .kind()
                                 .map_bound(|clause| match clause {
@@ -1776,7 +1774,8 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                                 fcx.param_env,
                                 predicate,
                             ))
-                        }),
+                        },
+                    ),
                 );
                 ocx.select_where_possible().is_empty()
             })