Rollup merge of #94146 - est31:let_else, r=cjgillot

Adopt let else in more places

Continuation of #89933, #91018, #91481, #93046, #93590, #94011.

I have extended my clippy lint to also recognize tuple passing and match statements. The diff caused by fixing it is way above 1 thousand lines. Thus, I split it up into multiple pull requests to make reviewing easier. This is the biggest of these PRs and handles the changes outside of rustdoc, rustc_typeck, rustc_const_eval, rustc_trait_selection, which were handled in PRs #94139, #94142, #94143, #94144.

compiler/rustc_middle/src/middle/region.rs

@@ -173,9 +173,8 @@ impl Scope {
     /// returned span may not correspond to the span of any `NodeId` in
     /// the AST.
     pub fn span(&self, tcx: TyCtxt<'_>, scope_tree: &ScopeTree) -> Span {
-        let hir_id = match self.hir_id(scope_tree) {
-            Some(hir_id) => hir_id,
-            None => return DUMMY_SP,
+        let Some(hir_id) = self.hir_id(scope_tree) else {
+            return DUMMY_SP;
         };
         let span = tcx.hir().span(hir_id);
         if let ScopeData::Remainder(first_statement_index) = self.data {

compiler/rustc_middle/src/mir/pretty.rs

@@ -89,9 +89,8 @@ pub fn dump_mir<'tcx, F>(
 }
 
 pub fn dump_enabled<'tcx>(tcx: TyCtxt<'tcx>, pass_name: &str, def_id: DefId) -> bool {
-    let filters = match tcx.sess.opts.debugging_opts.dump_mir {
-        None => return false,
-        Some(ref filters) => filters,
+    let Some(ref filters) = tcx.sess.opts.debugging_opts.dump_mir else {
+        return false;
     };
     let node_path = ty::print::with_forced_impl_filename_line(|| {
         // see notes on #41697 below
@@ -586,9 +585,8 @@ fn write_scope_tree(
         )?;
     }
 
-    let children = match scope_tree.get(&parent) {
-        Some(children) => children,
-        None => return Ok(()),
+    let Some(children) = scope_tree.get(&parent) else {
+        return Ok(());
     };
 
     for &child in children {

compiler/rustc_middle/src/ty/context.rs

@@ -1123,9 +1123,8 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn layout_scalar_valid_range(self, def_id: DefId) -> (Bound<u128>, Bound<u128>) {
         let attrs = self.get_attrs(def_id);
         let get = |name| {
-            let attr = match attrs.iter().find(|a| a.has_name(name)) {
-                Some(attr) => attr,
-                None => return Bound::Unbounded,
+            let Some(attr) = attrs.iter().find(|a| a.has_name(name)) else {
+                return Bound::Unbounded;
             };
             debug!("layout_scalar_valid_range: attr={:?}", attr);
             if let Some(
@@ -1513,9 +1512,8 @@ impl<'tcx> TyCtxt<'tcx> {
         scope_def_id: LocalDefId,
     ) -> Vec<&'tcx hir::Ty<'tcx>> {
         let hir_id = self.hir().local_def_id_to_hir_id(scope_def_id);
-        let hir_output = match self.hir().fn_decl_by_hir_id(hir_id) {
-            Some(hir::FnDecl { output: hir::FnRetTy::Return(ty), .. }) => ty,
-            _ => return vec![],
+        let Some(hir::FnDecl { output: hir::FnRetTy::Return(hir_output), .. }) = self.hir().fn_decl_by_hir_id(hir_id) else {
+            return vec![];
         };
 
         let mut v = TraitObjectVisitor(vec![], self.hir());

compiler/rustc_middle/src/ty/error.rs

@@ -861,11 +861,10 @@ fn foo(&self) -> Self::T { String::new() }
         body_owner_def_id: DefId,
         found: Ty<'tcx>,
     ) -> bool {
-        let hir_id =
-            match body_owner_def_id.as_local().map(|id| self.hir().local_def_id_to_hir_id(id)) {
-                Some(hir_id) => hir_id,
-                None => return false,
-            };
+        let Some(hir_id) = body_owner_def_id.as_local() else {
+            return false;
+        };
+        let hir_id = self.hir().local_def_id_to_hir_id(hir_id);
         // When `body_owner` is an `impl` or `trait` item, look in its associated types for
         // `expected` and point at it.
         let parent_id = self.hir().get_parent_item(hir_id);

compiler/rustc_middle/src/ty/layout.rs

@@ -1319,9 +1319,8 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                     // Try to use a ScalarPair for all tagged enums.
                     let mut common_prim = None;
                     for (field_layouts, layout_variant) in iter::zip(&variants, &layout_variants) {
-                        let offsets = match layout_variant.fields {
-                            FieldsShape::Arbitrary { ref offsets, .. } => offsets,
-                            _ => bug!(),
+                        let FieldsShape::Arbitrary { ref offsets, .. } = layout_variant.fields else {
+                            bug!();
                         };
                         let mut fields =
                             iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst());
@@ -1571,9 +1570,8 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         let tcx = self.tcx;
         let subst_field = |ty: Ty<'tcx>| ty.subst(tcx, substs);
 
-        let info = match tcx.generator_layout(def_id) {
-            None => return Err(LayoutError::Unknown(ty)),
-            Some(info) => info,
+        let Some(info) = tcx.generator_layout(def_id) else {
+            return Err(LayoutError::Unknown(ty));
         };
         let (ineligible_locals, assignments) = self.generator_saved_local_eligibility(&info);
 
@@ -1676,9 +1674,8 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                 )?;
                 variant.variants = Variants::Single { index };
 
-                let (offsets, memory_index) = match variant.fields {
-                    FieldsShape::Arbitrary { offsets, memory_index } => (offsets, memory_index),
-                    _ => bug!(),
+                let FieldsShape::Arbitrary { offsets, memory_index } = variant.fields else {
+                    bug!();
                 };
 
                 // Now, stitch the promoted and variant-only fields back together in

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -415,9 +415,8 @@ pub trait PrettyPrinter<'tcx>:
             cur_def_key = self.tcx().def_key(parent);
         }
 
-        let visible_parent = match visible_parent_map.get(&def_id).cloned() {
-            Some(parent) => parent,
-            None => return Ok((self, false)),
+        let Some(visible_parent) = visible_parent_map.get(&def_id).cloned() else {
+            return Ok((self, false));
         };
 
         let actual_parent = self.tcx().parent(def_id);