Adopt let else in more places

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1582,12 +1582,9 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
         def_id: DefId,
         span: Span,
     ) {
-        let variants = match self.collect_enum_ctors(def_id) {
-            Some(variants) => variants,
-            None => {
-                err.note("you might have meant to use one of the enum's variants");
-                return;
-            }
+        let Some(variants) = self.collect_enum_ctors(def_id) else {
+            err.note("you might have meant to use one of the enum's variants");
+            return;
         };
 
         let suggest_only_tuple_variants =

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -1748,10 +1748,7 @@ fn object_lifetime_defaults_for_item<'tcx>(
             let param_def_id = tcx.hir().local_def_id(param.hir_id);
             for predicate in generics.where_clause.predicates {
                 // Look for `type: ...` where clauses.
-                let data = match *predicate {
-                    hir::WherePredicate::BoundPredicate(ref data) => data,
-                    _ => continue,
-                };
+                let hir::WherePredicate::BoundPredicate(ref data) = *predicate else { continue };
 
                 // Ignore `for<'a> type: ...` as they can change what
                 // lifetimes mean (although we could "just" handle it).
@@ -1976,12 +1973,9 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
     }
 
     fn check_uses_for_lifetimes_defined_by_scope(&mut self) {
-        let defined_by = match self.scope {
-            Scope::Binder { lifetimes, .. } => lifetimes,
-            _ => {
-                debug!("check_uses_for_lifetimes_defined_by_scope: not in a binder scope");
-                return;
-            }
+        let Scope::Binder { lifetimes: defined_by, .. } = self.scope else {
+            debug!("check_uses_for_lifetimes_defined_by_scope: not in a binder scope");
+            return;
         };
 
         let def_ids: Vec<_> = defined_by
@@ -2636,9 +2630,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             smallvec![(def_id, smallvec![])];
         let mut visited: FxHashSet<DefId> = FxHashSet::default();
         loop {
-            let (def_id, bound_vars) = match stack.pop() {
-                Some(next) => next,
-                None => break None,
+            let Some((def_id, bound_vars)) = stack.pop() else {
+                break None;
             };
             // See issue #83753. If someone writes an associated type on a non-trait, just treat it as
             // there being no supertrait HRTBs.
@@ -2723,10 +2716,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             }
         });
 
-        let output = match output {
-            Some(ty) => ty,
-            None => return,
-        };
+        let Some(output) = output else { return };
 
         debug!("determine output");