Rollup merge of #93046 - est31:let_else, r=davidtwco

Use let_else in even more places

Followup of #89933, #91018, #91481.

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -1493,7 +1493,7 @@ fn generator_layout_and_saved_local_names<'tcx>(
 
     let state_arg = mir::Local::new(1);
     for var in &body.var_debug_info {
-        let place = if let mir::VarDebugInfoContents::Place(p) = var.value { p } else { continue };
+        let mir::VarDebugInfoContents::Place(place) = &var.value else { continue };
         if place.local != state_arg {
             continue;
         }

compiler/rustc_codegen_llvm/src/lib.rs

@@ -7,6 +7,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(bool_to_option)]
 #![feature(crate_visibility_modifier)]
+#![feature(let_else)]
 #![feature(extern_types)]
 #![feature(nll)]
 #![recursion_limit = "256"]

compiler/rustc_interface/src/lib.rs

@@ -1,5 +1,6 @@
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
+#![feature(let_else)]
 #![feature(internal_output_capture)]
 #![feature(thread_spawn_unchecked)]
 #![feature(nll)]

compiler/rustc_interface/src/util.rs

@@ -717,7 +717,9 @@ impl<'a, 'b> ReplaceBodyWithLoop<'a, 'b> {
     }
 
     fn should_ignore_fn(ret_ty: &ast::FnRetTy) -> bool {
-        if let ast::FnRetTy::Ty(ref ty) = ret_ty {
+        let ast::FnRetTy::Ty(ref ty) = ret_ty else {
+            return false;
+        };
         fn involves_impl_trait(ty: &ast::Ty) -> bool {
             match ty.kind {
                 ast::TyKind::ImplTrait(..) => true,
@@ -734,8 +736,9 @@ impl<'a, 'b> ReplaceBodyWithLoop<'a, 'b> {
                             data.args.iter().any(|arg| match arg {
                                 ast::AngleBracketedArg::Arg(arg) => match arg {
                                     ast::GenericArg::Type(ty) => involves_impl_trait(ty),
-                                        ast::GenericArg::Lifetime(_)
+                                    ast::GenericArg::Lifetime(_) | ast::GenericArg::Const(_) => {
-                                        | ast::GenericArg::Const(_) => false,
+                                        false
+                                    }
                                 },
                                 ast::AngleBracketedArg::Constraint(c) => match c.kind {
                                     ast::AssocConstraintKind::Bound { .. } => true,
@@ -765,9 +768,6 @@ impl<'a, 'b> ReplaceBodyWithLoop<'a, 'b> {
         }
 
         involves_impl_trait(ty)
-        } else {
-            false
-        }
     }
 
     fn is_sig_const(sig: &ast::FnSig) -> bool {

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -1347,7 +1347,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
         let mut otherwise = None;
         for match_pair in match_pairs {
-            if let PatKind::Or { ref pats } = *match_pair.pattern.kind {
+            let PatKind::Or { ref pats } = &*match_pair.pattern.kind else {
+                bug!("Or-patterns should have been sorted to the end");
+            };
             let or_span = match_pair.pattern.span;
             let place = match_pair.place;
 
@@ -1361,9 +1363,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     fake_borrows,
                 );
             });
-            } else {
-                bug!("Or-patterns should have been sorted to the end");
-            }
         }
 
         let remainder_start = otherwise.unwrap_or_else(|| self.cfg.start_new_block());

compiler/rustc_mir_build/src/build/matches/test.rs

@@ -88,11 +88,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         switch_ty: Ty<'tcx>,
         options: &mut FxIndexMap<&'tcx ty::Const<'tcx>, u128>,
     ) -> bool {
-        let match_pair = match candidate.match_pairs.iter().find(|mp| mp.place == *test_place) {
+        let Some(match_pair) = candidate.match_pairs.iter().find(|mp| mp.place == *test_place) else {
-            Some(match_pair) => match_pair,
-            _ => {
             return false;
-            }
         };
 
         match *match_pair.pattern.kind {

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1171,9 +1171,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
         ident: Symbol,
         kind: &AssocItemKind,
     ) -> Option<Symbol> {
-        let module = if let Some((module, _)) = self.current_trait_ref {
+        let Some((module, _)) = &self.current_trait_ref else {
-            module
-        } else {
             return None;
         };
         if ident == kw::Underscore {

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -1000,7 +1000,9 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 // `fn foo<'a>() -> MyAnonTy<'a> { ... }`
                 //          ^                 ^this gets resolved in the current scope
                 for lifetime in lifetimes {
-                    if let hir::GenericArg::Lifetime(lifetime) = lifetime {
+                    let hir::GenericArg::Lifetime(lifetime) = lifetime else {
+                        continue
+                    };
                     self.visit_lifetime(lifetime);
 
                     // Check for predicates like `impl for<'a> Trait<impl OtherTrait<'a>>`
@@ -1008,19 +1010,19 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     // well-supported at the moment, so this doesn't work.
                     // In the future, this should be fixed and this error should be removed.
                     let def = self.map.defs.get(&lifetime.hir_id).cloned();
-                        if let Some(Region::LateBound(_, _, def_id, _)) = def {
+                    let Some(Region::LateBound(_, _, def_id, _)) = def else {
-                            if let Some(def_id) = def_id.as_local() {
+                        continue
+                    };
+                    let Some(def_id) = def_id.as_local() else {
+                        continue
+                    };
                     let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
                     // Ensure that the parent of the def is an item, not HRTB
                     let parent_id = self.tcx.hir().get_parent_node(hir_id);
                     // FIXME(cjgillot) Can this check be replaced by
                     // `let parent_is_item = parent_id.is_owner();`?
-                                let parent_is_item =
+                    let parent_is_item = if let Some(parent_def_id) = parent_id.as_owner() {
-                                    if let Some(parent_def_id) = parent_id.as_owner() {
+                        matches!(self.tcx.hir().krate().owners.get(parent_def_id), Some(Some(_)),)
-                                        matches!(
-                                            self.tcx.hir().krate().owners.get(parent_def_id),
-                                            Some(Some(_)),
-                                        )
                     } else {
                         false
                     };
@@ -1039,9 +1041,6 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         self.uninsert_lifetime_on_error(lifetime, def.unwrap());
                     }
                 }
-                        }
-                    }
-                }
 
                 // We want to start our early-bound indices at the end of the parent scope,
                 // not including any parent `impl Trait`s.

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

@@ -840,7 +840,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             };
 
             for refs_remaining in 0..refs_number {
-                if let ty::Ref(_, inner_ty, _) = suggested_ty.kind() {
+                let ty::Ref(_, inner_ty, _) = suggested_ty.kind() else {
+                    break;
+                };
                 suggested_ty = inner_ty;
 
                 let new_obligation = self.mk_trait_obligation_with_new_self_ty(
@@ -872,9 +874,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     );
                     break;
                 }
-                } else {
-                    break;
-                }
             }
         }
     }