Rollup merge of #136464 - nnethercote:rm-TyCtxtAt-for-hooks, r=oli-obk

Remove hook calling via `TyCtxtAt`.

All hooks receive a `TyCtxtAt` argument.

Currently hooks can be called through `TyCtxtAt` or `TyCtxt`. In the latter case, a `TyCtxtAt` is constructed with a dummy span and passed to the hook.

However, in practice hooks are never called through `TyCtxtAt`, and always receive a dummy span. (I confirmed this via code inspection, and double-checked it by temporarily making the `TyCtxtAt` code path panic and running all the tests.)

This commit removes all the `TyCtxtAt` machinery for hooks. All hooks now receive `TyCtxt` instead of `TyCtxtAt`. There are two existing hooks that use `TyCtxtAt::span`: `const_caller_location_provider` and `try_destructure_mir_constant_for_user_output`. For both hooks the span is always a dummy span, probably unintentionally. This dummy span use is now explicit. If a non-dummy span is needed for these two hooks it would be easy to add it as an extra argument because hooks are less constrained than queries.

r? `@oli-obk`

compiler/rustc_monomorphize/src/collector.rs

@@ -953,7 +953,7 @@ fn visit_instance_use<'tcx>(
 
 /// Returns `true` if we should codegen an instance in the local crate, or returns `false` if we
 /// can just link to the upstream crate and therefore don't need a mono item.
-fn should_codegen_locally<'tcx>(tcx: TyCtxtAt<'tcx>, instance: Instance<'tcx>) -> bool {
+fn should_codegen_locally<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> bool {
     let Some(def_id) = instance.def.def_id_if_not_guaranteed_local_codegen() else {
         return true;
     };
@@ -976,7 +976,7 @@ fn should_codegen_locally<'tcx>(tcx: TyCtxtAt<'tcx>, instance: Instance<'tcx>) -
         return true;
     }
 
-    if tcx.is_reachable_non_generic(def_id) || instance.upstream_monomorphization(*tcx).is_some() {
+    if tcx.is_reachable_non_generic(def_id) || instance.upstream_monomorphization(tcx).is_some() {
         // We can link to the item in question, no instance needed in this crate.
         return false;
     }