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_builtin_macros/src/cfg_accessible.rs

@@ -44,9 +44,8 @@ impl MultiItemModifier for Expander {
             template,
         );
 
-        let path = match validate_input(ecx, meta_item) {
-            Some(path) => path,
-            None => return ExpandResult::Ready(Vec::new()),
+        let Some(path) = validate_input(ecx, meta_item) else {
+            return ExpandResult::Ready(Vec::new());
         };
 
         match ecx.resolver.cfg_accessible(ecx.current_expansion.id, path) {

compiler/rustc_builtin_macros/src/compile_error.rs

@@ -9,9 +9,8 @@ pub fn expand_compile_error<'cx>(
     sp: Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'cx> {
-    let var = match get_single_str_from_tts(cx, sp, tts, "compile_error!") {
-        None => return DummyResult::any(sp),
-        Some(v) => v,
+    let Some(var) = get_single_str_from_tts(cx, sp, tts, "compile_error!") else {
+        return DummyResult::any(sp);
     };
 
     cx.span_err(sp, &var);

compiler/rustc_builtin_macros/src/concat.rs

@@ -10,9 +10,8 @@ pub fn expand_concat(
     sp: rustc_span::Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
-    let es = match base::get_exprs_from_tts(cx, sp, tts) {
-        Some(e) => e,
-        None => return DummyResult::any(sp),
+    let Some(es) = base::get_exprs_from_tts(cx, sp, tts) else {
+        return DummyResult::any(sp);
     };
     let mut accumulator = String::new();
     let mut missing_literal = vec![];

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -121,9 +121,8 @@ pub fn expand_concat_bytes(
     sp: rustc_span::Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
-    let es = match base::get_exprs_from_tts(cx, sp, tts) {
-        Some(e) => e,
-        None => return DummyResult::any(sp),
+    let Some(es) = base::get_exprs_from_tts(cx, sp, tts) else {
+        return DummyResult::any(sp);
     };
     let mut accumulator = Vec::new();
     let mut missing_literals = vec![];

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -196,12 +196,11 @@ fn cs_clone(
             let fields = all_fields
                 .iter()
                 .map(|field| {
-                    let ident = match field.name {
-                        Some(i) => i,
-                        None => cx.span_bug(
+                    let Some(ident) = field.name else {
+                        cx.span_bug(
                             trait_span,
                             &format!("unnamed field in normal struct in `derive({})`", name,),
-                        ),
+                        );
                     };
                     let call = subcall(cx, field);
                     cx.field_imm(field.span, ident, call)

compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs

@@ -83,9 +83,8 @@ pub fn cs_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<
             // }
 
             let new = {
-                let other_f = match other_fs {
-                    [o_f] => o_f,
-                    _ => cx.span_bug(span, "not exactly 2 arguments in `derive(Ord)`"),
+                let [other_f] = other_fs else {
+                    cx.span_bug(span, "not exactly 2 arguments in `derive(Ord)`");
                 };
 
                 let args =

compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -26,9 +26,8 @@ pub fn expand_deriving_partial_eq(
         base: bool,
     ) -> P<Expr> {
         let op = |cx: &mut ExtCtxt<'_>, span: Span, self_f: P<Expr>, other_fs: &[P<Expr>]| {
-            let other_f = match other_fs {
-                [o_f] => o_f,
-                _ => cx.span_bug(span, "not exactly 2 arguments in `derive(PartialEq)`"),
+            let [other_f] = other_fs else {
+                cx.span_bug(span, "not exactly 2 arguments in `derive(PartialEq)`");
             };
 
             cx.expr_binary(span, op, self_f, other_f.clone())

compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs

@@ -86,9 +86,8 @@ pub fn cs_partial_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_
             // }
 
             let new = {
-                let other_f = match other_fs {
-                    [o_f] => o_f,
-                    _ => cx.span_bug(span, "not exactly 2 arguments in `derive(PartialOrd)`"),
+                let [other_f] = other_fs else {
+                    cx.span_bug(span, "not exactly 2 arguments in `derive(PartialOrd)`");
                 };
 
                 let args =

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -101,9 +101,8 @@ fn default_enum_substructure(
     trait_span: Span,
     enum_def: &EnumDef,
 ) -> P<Expr> {
-    let default_variant = match extract_default_variant(cx, enum_def, trait_span) {
-        Ok(value) => value,
-        Err(()) => return DummyResult::raw_expr(trait_span, true),
+    let Ok(default_variant) = extract_default_variant(cx, enum_def, trait_span) else {
+        return DummyResult::raw_expr(trait_span, true);
     };
 
     // At this point, we know that there is exactly one variant with a `#[default]` attribute. The

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -48,9 +48,8 @@ pub fn expand_deriving_hash(
 }
 
 fn hash_substructure(cx: &mut ExtCtxt<'_>, trait_span: Span, substr: &Substructure<'_>) -> P<Expr> {
-    let state_expr = match substr.nonself_args {
-        [o_f] => o_f,
-        _ => cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`"),
+    let [state_expr] = substr.nonself_args else {
+        cx.span_bug(trait_span, "incorrect number of arguments in `derive(Hash)`");
     };
     let call_hash = |span, thing_expr| {
         let hash_path = {

compiler/rustc_builtin_macros/src/deriving/mod.rs

@@ -116,9 +116,8 @@ fn inject_impl_of_structural_trait(
     structural_path: generic::ty::Path,
     push: &mut dyn FnMut(Annotatable),
 ) {
-    let item = match *item {
-        Annotatable::Item(ref item) => item,
-        _ => unreachable!(),
+    let Annotatable::Item(ref item) = *item else {
+        unreachable!();
     };
 
     let generics = match item.kind {

compiler/rustc_builtin_macros/src/env.rs

@@ -16,9 +16,8 @@ pub fn expand_option_env<'cx>(
     sp: Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'cx> {
-    let var = match get_single_str_from_tts(cx, sp, tts, "option_env!") {
-        None => return DummyResult::any(sp),
-        Some(v) => v,
+    let Some(var) = get_single_str_from_tts(cx, sp, tts, "option_env!") else {
+        return DummyResult::any(sp);
     };
 
     let sp = cx.with_def_site_ctxt(sp);
@@ -62,9 +61,8 @@ pub fn expand_env<'cx>(
         Some(exprs) => exprs.into_iter(),
     };
 
-    let var = match expr_to_string(cx, exprs.next().unwrap(), "expected string literal") {
-        None => return DummyResult::any(sp),
-        Some((v, _style)) => v,
+    let Some((var, _style)) = expr_to_string(cx, exprs.next().unwrap(), "expected string literal") else {
+        return DummyResult::any(sp);
     };
     let msg = match exprs.next() {
         None => Symbol::intern(&format!("environment variable `{}` not defined", var)),

compiler/rustc_builtin_macros/src/proc_macro_harness.rs

@@ -103,11 +103,9 @@ impl<'a> CollectProcMacros<'a> {
     }
 
     fn collect_custom_derive(&mut self, item: &'a ast::Item, attr: &'a ast::Attribute) {
-        let (trait_name, proc_attrs) =
-            match parse_macro_name_and_helper_attrs(self.handler, attr, "derive") {
-                Some(name_and_attrs) => name_and_attrs,
-                None => return,
-            };
+        let Some((trait_name, proc_attrs)) = parse_macro_name_and_helper_attrs(self.handler, attr, "derive") else {
+            return;
+        };
 
         if self.in_root && item.vis.kind.is_pub() {
             self.macros.push(ProcMacro::Derive(ProcMacroDerive {
@@ -219,15 +217,12 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
             }
         }
 
-        let attr = match found_attr {
-            None => {
-                self.check_not_pub_in_root(&item.vis, self.source_map.guess_head_span(item.span));
-                let prev_in_root = mem::replace(&mut self.in_root, false);
-                visit::walk_item(self, item);
-                self.in_root = prev_in_root;
-                return;
-            }
-            Some(attr) => attr,
+        let Some(attr) = found_attr else {
+            self.check_not_pub_in_root(&item.vis, self.source_map.guess_head_span(item.span));
+            let prev_in_root = mem::replace(&mut self.in_root, false);
+            visit::walk_item(self, item);
+            self.in_root = prev_in_root;
+            return;
         };
 
         if !is_fn {

compiler/rustc_builtin_macros/src/source_util.rs

@@ -98,9 +98,8 @@ pub fn expand_include<'cx>(
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'cx> {
     let sp = cx.with_def_site_ctxt(sp);
-    let file = match get_single_str_from_tts(cx, sp, tts, "include!") {
-        Some(f) => f,
-        None => return DummyResult::any(sp),
+    let Some(file) = get_single_str_from_tts(cx, sp, tts, "include!") else {
+        return DummyResult::any(sp);
     };
     // The file will be added to the code map by the parser
     let file = match cx.resolve_path(file, sp) {
@@ -169,9 +168,8 @@ pub fn expand_include_str(
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
     let sp = cx.with_def_site_ctxt(sp);
-    let file = match get_single_str_from_tts(cx, sp, tts, "include_str!") {
-        Some(f) => f,
-        None => return DummyResult::any(sp),
+    let Some(file) = get_single_str_from_tts(cx, sp, tts, "include_str!") else {
+        return DummyResult::any(sp);
     };
     let file = match cx.resolve_path(file, sp) {
         Ok(f) => f,
@@ -204,9 +202,8 @@ pub fn expand_include_bytes(
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
     let sp = cx.with_def_site_ctxt(sp);
-    let file = match get_single_str_from_tts(cx, sp, tts, "include_bytes!") {
-        Some(f) => f,
-        None => return DummyResult::any(sp),
+    let Some(file) = get_single_str_from_tts(cx, sp, tts, "include_bytes!") else {
+        return DummyResult::any(sp);
     };
     let file = match cx.resolve_path(file, sp) {
         Ok(f) => f,