Auto merge of #108127 - matthiaskrgr:rollup-kpzfc6j, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #106347 (More accurate spans for arg removal suggestion)
 - #108057 (Prevent some attributes from being merged with others on reexports)
 - #108090 (`if $c:expr { Some($r:expr) } else { None }` =>> `$c.then(|| $r)`)
 - #108092 (note issue for feature(packed_bundled_libs))
 - #108099 (use chars instead of strings where applicable)
 - #108115 (Do not ICE on unmet trait alias bounds)
 - #108125 (Add new people to the compiletest review rotation)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -82,11 +82,8 @@ impl<'tcx, 'a> GeneratorData<'tcx, 'a> {
                     upvars.iter().find_map(|(upvar_id, upvar)| {
                         let upvar_ty = typeck_results.node_type(*upvar_id);
                         let upvar_ty = infer_context.resolve_vars_if_possible(upvar_ty);
-                        if ty_matches(ty::Binder::dummy(upvar_ty)) {
-                            Some(GeneratorInteriorOrUpvar::Upvar(upvar.span))
-                        } else {
-                            None
-                        }
+                        ty_matches(ty::Binder::dummy(upvar_ty))
+                            .then(|| GeneratorInteriorOrUpvar::Upvar(upvar.span))
                     })
                 })
             }
@@ -770,15 +767,13 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                             obligation.param_env,
                             real_trait_pred_and_ty,
                         );
-                        if obligations
+                        let may_hold = obligations
                             .iter()
                             .chain([&obligation])
                             .all(|obligation| self.predicate_may_hold(obligation))
-                        {
-                            Some(steps)
-                        } else {
-                            None
-                        }
+                            .then_some(steps);
+
+                        may_hold
                     })
                 {
                     if steps > 0 {

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -523,16 +523,14 @@ fn is_impossible_method(tcx: TyCtxt<'_>, (impl_def_id, trait_item_def_id): (DefI
 
     let mut visitor = ReferencesOnlyParentGenerics { tcx, generics, trait_item_def_id };
     let predicates_for_trait = predicates.predicates.iter().filter_map(|(pred, span)| {
-        if pred.visit_with(&mut visitor).is_continue() {
-            Some(Obligation::new(
+        pred.visit_with(&mut visitor).is_continue().then(|| {
+            Obligation::new(
                 tcx,
                 ObligationCause::dummy_with_span(*span),
                 param_env,
                 ty::EarlyBinder(*pred).subst(tcx, impl_trait_ref.substs),
-            ))
-        } else {
-            None
-        }
+            )
+        })
     });
 
     let infcx = tcx.infer_ctxt().ignoring_regions().build();

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -307,7 +307,7 @@ fn predicate_references_self<'tcx>(
     match predicate.kind().skip_binder() {
         ty::PredicateKind::Clause(ty::Clause::Trait(ref data)) => {
             // In the case of a trait predicate, we can skip the "self" type.
-            if data.trait_ref.substs[1..].iter().any(has_self_ty) { Some(sp) } else { None }
+            data.trait_ref.substs[1..].iter().any(has_self_ty).then_some(sp)
         }
         ty::PredicateKind::Clause(ty::Clause::Projection(ref data)) => {
             // And similarly for projections. This should be redundant with
@@ -325,7 +325,7 @@ fn predicate_references_self<'tcx>(
             //
             // This is ALT2 in issue #56288, see that for discussion of the
             // possible alternatives.
-            if data.projection_ty.substs[1..].iter().any(has_self_ty) { Some(sp) } else { None }
+            data.projection_ty.substs[1..].iter().any(has_self_ty).then_some(sp)
         }
         ty::PredicateKind::AliasEq(..) => bug!("`AliasEq` not allowed as assumption"),
 

compiler/rustc_trait_selection/src/traits/query/type_op/outlives.rs

@@ -21,11 +21,7 @@ impl<'tcx> super::QueryTypeOp<'tcx> for DropckOutlives<'tcx> {
         tcx: TyCtxt<'tcx>,
         key: &ParamEnvAnd<'tcx, Self>,
     ) -> Option<Self::QueryResponse> {
-        if trivial_dropck_outlives(tcx, key.value.dropped_ty) {
-            Some(DropckOutlivesResult::default())
-        } else {
-            None
-        }
+        trivial_dropck_outlives(tcx, key.value.dropped_ty).then(DropckOutlivesResult::default)
     }
 
     fn perform_query(

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -378,11 +378,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                             let self_ty = trait_ref.self_ty();
                             let (trait_desc, self_desc) = with_no_trimmed_paths!({
                                 let trait_desc = trait_ref.print_only_trait_path().to_string();
-                                let self_desc = if self_ty.has_concrete_skeleton() {
-                                    Some(self_ty.to_string())
-                                } else {
-                                    None
-                                };
+                                let self_desc =
+                                    self_ty.has_concrete_skeleton().then(|| self_ty.to_string());
                                 (trait_desc, self_desc)
                             });
                             let cause = if let Conflict::Upstream = conflict {

compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs

@@ -113,7 +113,7 @@ impl<'tcx> ChildrenExt<'tcx> for Children {
                     // Only report the `Self` type if it has at least
                     // some outer concrete shell; otherwise, it's
                     // not adding much information.
-                    self_ty: if self_ty.has_concrete_skeleton() { Some(self_ty) } else { None },
+                    self_ty: self_ty.has_concrete_skeleton().then_some(self_ty),
                     intercrate_ambiguity_causes: overlap.intercrate_ambiguity_causes,
                     involves_placeholder: overlap.involves_placeholder,
                 }