rustc_typeck: adopt let else in more places

Author: est31

compiler/rustc_typeck/src/astconv/mod.rs

@@ -1808,12 +1808,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             (_, Res::SelfTy { trait_: Some(_), alias_to: Some((impl_def_id, _)) }) => {
                 // `Self` in an impl of a trait -- we have a concrete self type and a
                 // trait reference.
-                let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
-                    Some(trait_ref) => trait_ref,
-                    None => {
-                        // A cycle error occurred, most likely.
-                        return Err(ErrorReported);
-                    }
+                let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) else {
+                    // A cycle error occurred, most likely.
+                    return Err(ErrorReported);
                 };
 
                 self.one_bound_for_assoc_type(

compiler/rustc_typeck/src/check/callee.rs

@@ -219,10 +219,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             (self.tcx.lang_items().fn_mut_trait(), Ident::with_dummy_span(sym::call_mut), true),
             (self.tcx.lang_items().fn_once_trait(), Ident::with_dummy_span(sym::call_once), false),
         ] {
-            let trait_def_id = match opt_trait_def_id {
-                Some(def_id) => def_id,
-                None => continue,
-            };
+            let Some(trait_def_id) = opt_trait_def_id else { continue };
 
             let opt_input_types = opt_arg_exprs.map(|arg_exprs| {
                 [self.tcx.mk_tup(arg_exprs.iter().map(|e| {
@@ -246,11 +243,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if borrow {
                     // Check for &self vs &mut self in the method signature. Since this is either
                     // the Fn or FnMut trait, it should be one of those.
-                    let (region, mutbl) = if let ty::Ref(r, _, mutbl) =
-                        method.sig.inputs()[0].kind()
-                    {
-                        (r, mutbl)
-                    } else {
+                    let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind() else {
                         // The `fn`/`fn_mut` lang item is ill-formed, which should have
                         // caused an error elsewhere.
                         self.tcx

compiler/rustc_typeck/src/check/cast.rs

@@ -799,21 +799,19 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         let expr_kind = fcx.pointer_kind(m_expr.ty, self.span)?;
         let cast_kind = fcx.pointer_kind(m_cast.ty, self.span)?;
 
-        let cast_kind = match cast_kind {
+        let Some(cast_kind) = cast_kind else {
             // We can't cast if target pointer kind is unknown
-            None => return Err(CastError::UnknownCastPtrKind),
-            Some(cast_kind) => cast_kind,
+            return Err(CastError::UnknownCastPtrKind);
         };
 
         // Cast to thin pointer is OK
         if cast_kind == PointerKind::Thin {
             return Ok(CastKind::PtrPtrCast);
         }
 
-        let expr_kind = match expr_kind {
+        let Some(expr_kind) = expr_kind else {
             // We can't cast to fat pointer if source pointer kind is unknown
-            None => return Err(CastError::UnknownExprPtrKind),
-            Some(expr_kind) => expr_kind,
+            return Err(CastError::UnknownExprPtrKind);
         };
 
         // thin -> fat? report invalid cast (don't complain about vtable kinds)

compiler/rustc_typeck/src/check/check.rs

@@ -415,13 +415,10 @@ fn check_static_inhabited<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Spa
     // have UB during initialization if they are uninhabited, but there also seems to be no good
     // reason to allow any statics to be uninhabited.
     let ty = tcx.type_of(def_id);
-    let layout = match tcx.layout_of(ParamEnv::reveal_all().and(ty)) {
-        Ok(l) => l,
-        Err(_) => {
-            // Generic statics are rejected, but we still reach this case.
-            tcx.sess.delay_span_bug(span, "generic static must be rejected");
-            return;
-        }
+    let Ok(layout) = tcx.layout_of(ParamEnv::reveal_all().and(ty)) else {
+        // Generic statics are rejected, but we still reach this case.
+        tcx.sess.delay_span_bug(span, "generic static must be rejected");
+        return;
     };
     if layout.abi.is_uninhabited() {
         tcx.struct_span_lint_hir(
@@ -852,10 +849,7 @@ pub(super) fn check_specialization_validity<'tcx>(
     impl_id: DefId,
     impl_item: &hir::ImplItemRef,
 ) {
-    let ancestors = match trait_def.ancestors(tcx, impl_id) {
-        Ok(ancestors) => ancestors,
-        Err(_) => return,
-    };
+    let Ok(ancestors) = trait_def.ancestors(tcx, impl_id) else { return };
     let mut ancestor_impls = ancestors.skip(1).filter_map(|parent| {
         if parent.is_from_trait() {
             None

compiler/rustc_typeck/src/check/closure.rs

@@ -676,12 +676,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // We do not expect any bound regions in our predicate, so
         // skip past the bound vars.
-        let predicate = match predicate.no_bound_vars() {
-            Some(p) => p,
-            None => {
-                debug!("deduce_future_output_from_projection: has late-bound regions");
-                return None;
-            }
+        let Some(predicate) = predicate.no_bound_vars() else {
+            debug!("deduce_future_output_from_projection: has late-bound regions");
+            return None;
         };
 
         // Check that this is a projection from the `Future` trait.

compiler/rustc_typeck/src/check/coercion.rs

@@ -429,13 +429,10 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         // (e.g., in example above, the failure from relating `Vec<T>`
         // to the target type), since that should be the least
         // confusing.
-        let InferOk { value: ty, mut obligations } = match found {
-            Some(d) => d,
-            None => {
-                let err = first_error.expect("coerce_borrowed_pointer had no error");
-                debug!("coerce_borrowed_pointer: failed with err = {:?}", err);
-                return Err(err);
-            }
+        let Some(InferOk { value: ty, mut obligations }) = found else {
+            let err = first_error.expect("coerce_borrowed_pointer had no error");
+            debug!("coerce_borrowed_pointer: failed with err = {:?}", err);
+            return Err(err);
         };
 
         if ty == a && mt_a.mutbl == hir::Mutability::Not && autoderef.step_count() == 1 {
@@ -461,9 +458,8 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
 
         // Now apply the autoref. We have to extract the region out of
         // the final ref type we got.
-        let r_borrow = match ty.kind() {
-            ty::Ref(r_borrow, _, _) => r_borrow,
-            _ => span_bug!(span, "expected a ref type, got {:?}", ty),
+        let ty::Ref(r_borrow, _, _) = ty.kind() else {
+            span_bug!(span, "expected a ref type, got {:?}", ty);
         };
         let mutbl = match mutbl_b {
             hir::Mutability::Not => AutoBorrowMutability::Not,
@@ -944,9 +940,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // We don't ever need two-phase here since we throw out the result of the coercion
         let coerce = Coerce::new(self, cause, AllowTwoPhase::No);
         self.probe(|_| {
-            let ok = match coerce.coerce(source, target) {
-                Ok(ok) => ok,
-                _ => return false,
+            let Ok(ok) = coerce.coerce(source, target) else {
+                return false;
             };
             let mut fcx = traits::FulfillmentContext::new_in_snapshot();
             fcx.register_predicate_obligations(self, ok.obligations);

compiler/rustc_typeck/src/check/demand.rs

@@ -435,44 +435,39 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// opt.map(|param| { takes_ref(param) });
     /// ```
     fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> {
-        let path = match expr.kind {
-            hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) => path,
-            _ => return None,
+        let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else {
+            return None;
         };
 
-        let local_id = match path.res {
-            hir::def::Res::Local(id) => id,
-            _ => return None,
+        let hir::def::Res::Local(local_id) = path.res else {
+            return None;
         };
 
         let local_parent = self.tcx.hir().get_parent_node(local_id);
-        let param_hir_id = match self.tcx.hir().find(local_parent) {
-            Some(Node::Param(hir::Param { hir_id, .. })) => hir_id,
-            _ => return None,
+        let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else {
+            return None;
         };
 
         let param_parent = self.tcx.hir().get_parent_node(*param_hir_id);
-        let (expr_hir_id, closure_fn_decl) = match self.tcx.hir().find(param_parent) {
-            Some(Node::Expr(hir::Expr {
-                hir_id,
-                kind: hir::ExprKind::Closure(_, decl, ..),
-                ..
-            })) => (hir_id, decl),
-            _ => return None,
+        let Some(Node::Expr(hir::Expr {
+            hir_id: expr_hir_id,
+            kind: hir::ExprKind::Closure(_, closure_fn_decl, ..),
+            ..
+        })) = self.tcx.hir().find(param_parent) else {
+            return None;
         };
 
         let expr_parent = self.tcx.hir().get_parent_node(*expr_hir_id);
         let hir = self.tcx.hir().find(expr_parent);
         let closure_params_len = closure_fn_decl.inputs.len();
-        let (method_path, method_expr) = match (hir, closure_params_len) {
-            (
-                Some(Node::Expr(hir::Expr {
-                    kind: hir::ExprKind::MethodCall(segment, expr, _),
-                    ..
-                })),
-                1,
-            ) => (segment, expr),
-            _ => return None,
+        let (
+            Some(Node::Expr(hir::Expr {
+                kind: hir::ExprKind::MethodCall(method_path, method_expr, _),
+                ..
+            })),
+            1,
+        ) = (hir, closure_params_len) else {
+            return None;
         };
 
         let self_ty = self.typeck_results.borrow().node_type(method_expr[0].hir_id);

compiler/rustc_typeck/src/check/expr.rs

@@ -622,15 +622,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // the `enclosing_loops` field and let's coerce the
             // type of `expr_opt` into what is expected.
             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
-            let ctxt = match enclosing_breakables.opt_find_breakable(target_id) {
-                Some(ctxt) => ctxt,
-                None => {
-                    // Avoid ICE when `break` is inside a closure (#65383).
-                    return tcx.ty_error_with_message(
-                        expr.span,
-                        "break was outside loop, but no error was emitted",
-                    );
-                }
+            let Some(ctxt) = enclosing_breakables.opt_find_breakable(target_id) else {
+                // Avoid ICE when `break` is inside a closure (#65383).
+                return tcx.ty_error_with_message(
+                    expr.span,
+                    "break was outside loop, but no error was emitted",
+                );
             };
 
             if let Some(ref mut coerce) = ctxt.coerce {

compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs

@@ -745,10 +745,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         formal_args: &[Ty<'tcx>],
     ) -> Vec<Ty<'tcx>> {
         let formal_ret = self.resolve_vars_with_obligations(formal_ret);
-        let ret_ty = match expected_ret.only_has_type(self) {
-            Some(ret) => ret,
-            None => return Vec::new(),
-        };
+        let Some(ret_ty) = expected_ret.only_has_type(self) else { return Vec::new() };
         let expect_args = self
             .fudge_inference_if_ok(|| {
                 // Attempt to apply a subtyping relationship between the formal
@@ -1044,9 +1041,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Be helpful when the user wrote `{... expr;}` and
         // taking the `;` off is enough to fix the error.
         let last_stmt = blk.stmts.last()?;
-        let last_expr = match last_stmt.kind {
-            hir::StmtKind::Semi(ref e) => e,
-            _ => return None,
+        let hir::StmtKind::Semi(ref last_expr) = last_stmt.kind else {
+            return None;
         };
         let last_expr_ty = self.node_ty(last_expr.hir_id);
         let needs_box = match (last_expr_ty.kind(), expected_ty.kind()) {
@@ -1061,11 +1057,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     last_def_id, last_bounds, exp_def_id, exp_bounds
                 );
 
-                let (last_local_id, exp_local_id) =
-                    match (last_def_id.as_local(), exp_def_id.as_local()) {
-                        (Some(last_hir_id), Some(exp_hir_id)) => (last_hir_id, exp_hir_id),
-                        (_, _) => return None,
-                    };
+                let last_local_id = last_def_id.as_local()?;
+                let exp_local_id = exp_def_id.as_local()?;
 
                 match (
                     &self.tcx.hir().expect_item(last_local_id).kind,

compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs

@@ -434,9 +434,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // is and we were expecting a Box, ergo Pin<Box<expected>>, we
                 // can suggest Box::pin.
                 let parent = self.tcx.hir().get_parent_node(expr.hir_id);
-                let fn_name = match self.tcx.hir().find(parent) {
-                    Some(Node::Expr(Expr { kind: ExprKind::Call(fn_name, _), .. })) => fn_name,
-                    _ => return false,
+                let Some(Node::Expr(Expr { kind: ExprKind::Call(fn_name, _), .. })) = self.tcx.hir().find(parent) else {
+                    return false;
                 };
                 match fn_name.kind {
                     ExprKind::Path(QPath::TypeRelative(