Rollup merge of #118396 - compiler-errors:ast-lang-items, r=cjgillot

Collect lang items from AST, get rid of `GenericBound::LangItemTrait`

r? `@cjgillot`
cc #115178

Looking forward, the work to remove `QPath::LangItem` will also be significantly more difficult, but I plan on doing it as well. Specifically, we have to change:
1. A lot of `rustc_ast_lowering` for things like expr `..`
2. A lot of astconv, since we actually instantiate lang and non-lang paths quite differently.
3. A ton of diagnostics and clippy lints that are special-cased via `QPath::LangItem`

Meanwhile, it was pretty easy to remove `GenericBound::LangItemTrait`, so I just did that here.

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -938,32 +938,6 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
         }
     }
 
-    fn visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>) {
-        match bound {
-            hir::GenericBound::LangItemTrait(_, _, hir_id, _) => {
-                // FIXME(jackh726): This is pretty weird. `LangItemTrait` doesn't go
-                // through the regular poly trait ref code, so we don't get another
-                // chance to introduce a binder. For now, I'm keeping the existing logic
-                // of "if there isn't a Binder scope above us, add one", but I
-                // imagine there's a better way to go about this.
-                let (binders, scope_type) = self.poly_trait_ref_binder_info();
-
-                self.record_late_bound_vars(*hir_id, binders);
-                let scope = Scope::Binder {
-                    hir_id: *hir_id,
-                    bound_vars: FxIndexMap::default(),
-                    s: self.scope,
-                    scope_type,
-                    where_bound_origin: None,
-                };
-                self.with(scope, |this| {
-                    intravisit::walk_param_bound(this, bound);
-                });
-            }
-            _ => intravisit::walk_param_bound(self, bound),
-        }
-    }
-
     fn visit_poly_trait_ref(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) {
         self.visit_poly_trait_ref_inner(trait_ref, NonLifetimeBinderAllowed::Allow);
     }