Auto merge of #91505 - matthiaskrgr:rollup-orxgsxo, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #90538 (Document how recursion is handled for `ty::Ty`)
 - #90851 (Add unchecked downcast methods)
 - #91209 (Implement ``@snapshot`` check for htmldocck)
 - #91385 (Suggest the `pat_param` specifier before `|` on 2021 edition )
 - #91478 (Remove incorrect newline from float cast suggestion)
 - #91481 (Use let_else in some more places in rustc_lint)
 - #91488 (Fix ICE when `yield`ing in function returning `impl Trait`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_borrowck/src/type_check/input_output.rs

@@ -117,9 +117,29 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             }
         }
 
-        assert!(body.yield_ty().is_some() == universal_regions.yield_ty.is_some());
-        if let Some(mir_yield_ty) = body.yield_ty() {
-            let ur_yield_ty = universal_regions.yield_ty.unwrap();
+        debug!(
+            "equate_inputs_and_outputs: body.yield_ty {:?}, universal_regions.yield_ty {:?}",
+            body.yield_ty(),
+            universal_regions.yield_ty
+        );
+
+        // We will not have a universal_regions.yield_ty if we yield (by accident)
+        // outside of a generator and return an `impl Trait`, so emit a delay_span_bug
+        // because we don't want to panic in an assert here if we've already got errors.
+        if body.yield_ty().is_some() != universal_regions.yield_ty.is_some() {
+            self.tcx().sess.delay_span_bug(
+                body.span,
+                &format!(
+                    "Expected body to have yield_ty ({:?}) iff we have a UR yield_ty ({:?})",
+                    body.yield_ty(),
+                    universal_regions.yield_ty,
+                ),
+            );
+        }
+
+        if let (Some(mir_yield_ty), Some(ur_yield_ty)) =
+            (body.yield_ty(), universal_regions.yield_ty)
+        {
             let yield_span = body.local_decls[RETURN_PLACE].source_info.span;
             self.equate_normalized_input_or_output(ur_yield_ty, mir_yield_ty, yield_span);
         }

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -1027,6 +1027,24 @@ fn check_matcher_core(
                                 ),
                             );
                             err.span_label(sp, format!("not allowed after `{}` fragments", kind));
+
+                            if kind == NonterminalKind::PatWithOr
+                                && sess.edition == Edition::Edition2021
+                                && next_token.is_token(&BinOp(token::BinOpToken::Or))
+                            {
+                                let suggestion = quoted_tt_to_string(&TokenTree::MetaVarDecl(
+                                    span,
+                                    name,
+                                    Some(NonterminalKind::PatParam { inferred: false }),
+                                ));
+                                err.span_suggestion(
+                                    span,
+                                    &format!("try a `pat_param` fragment specifier instead"),
+                                    suggestion,
+                                    Applicability::MaybeIncorrect,
+                                );
+                            }
+
                             let msg = "allowed there are: ";
                             match possible {
                                 &[] => {}

compiler/rustc_lint/src/array_into_iter.rs

@@ -79,9 +79,8 @@ impl<'tcx> LateLintPass<'tcx> for ArrayIntoIter {
             let receiver_ty = cx.typeck_results().expr_ty(receiver_arg);
             let adjustments = cx.typeck_results().expr_adjustments(receiver_arg);
 
-            let target = match adjustments.last() {
-                Some(Adjustment { kind: Adjust::Borrow(_), target }) => target,
-                _ => return,
+            let Some(Adjustment { kind: Adjust::Borrow(_), target }) = adjustments.last() else {
+                return
             };
 
             let types =

compiler/rustc_lint/src/builtin.rs

@@ -609,14 +609,12 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
                 // If the trait is private, add the impl items to `private_traits` so they don't get
                 // reported for missing docs.
                 let real_trait = trait_ref.path.res.def_id();
-                if let Some(def_id) = real_trait.as_local() {
-                    let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
-                    if let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) {
-                        if let hir::VisibilityKind::Inherited = item.vis.node {
-                            for impl_item_ref in items {
-                                self.private_traits.insert(impl_item_ref.id.hir_id());
-                            }
-                        }
+                let Some(def_id) = real_trait.as_local() else { return };
+                let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id);
+                let Some(Node::Item(item)) = cx.tcx.hir().find(hir_id) else { return };
+                if let hir::VisibilityKind::Inherited = item.vis.node {
+                    for impl_item_ref in items {
+                        self.private_traits.insert(impl_item_ref.id.hir_id());
                     }
                 }
                 return;
@@ -829,9 +827,8 @@ impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
             _ => return,
         }
 
-        let debug = match cx.tcx.get_diagnostic_item(sym::Debug) {
-            Some(debug) => debug,
-            None => return,
+        let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
+            return
         };
 
         if self.impling_types.is_none() {
@@ -1509,9 +1506,8 @@ impl TypeAliasBounds {
 
 impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
-        let (ty, type_alias_generics) = match item.kind {
-            hir::ItemKind::TyAlias(ref ty, ref generics) => (&*ty, generics),
-            _ => return,
+        let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
+            return
         };
         if let hir::TyKind::OpaqueDef(..) = ty.kind {
             // Bounds are respected for `type X = impl Trait`
@@ -2266,16 +2262,15 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
                         // and should check for them here.
                         match predicate.bounded_ty.kind {
                             hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
-                                if let Res::Def(DefKind::TyParam, def_id) = path.res {
-                                    let index = ty_generics.param_def_id_to_index[&def_id];
-                                    (
-                                        Self::lifetimes_outliving_type(inferred_outlives, index),
-                                        &predicate.bounds,
-                                        predicate.span,
-                                    )
-                                } else {
-                                    continue;
-                                }
+                                let Res::Def(DefKind::TyParam, def_id) = path.res else {
+                                    continue
+                                };
+                                let index = ty_generics.param_def_id_to_index[&def_id];
+                                (
+                                    Self::lifetimes_outliving_type(inferred_outlives, index),
+                                    &predicate.bounds,
+                                    predicate.span,
+                                )
                             }
                             _ => {
                                 continue;
@@ -3216,18 +3211,17 @@ impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
                     for (idx, _) in statement.match_indices(':') {
                         let possible_label = statement[start_idx..idx].trim();
                         let mut chars = possible_label.chars();
-                        if let Some(c) = chars.next() {
-                            // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
-                            if (c.is_alphabetic() || matches!(c, '.' | '_'))
-                                && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
-                            {
-                                found_labels.push(possible_label);
-                            } else {
-                                // If we encounter a non-label, there cannot be any further labels, so stop checking
-                                break;
-                            }
-                        } else {
+                        let Some(c) = chars.next() else {
                             // Empty string means a leading ':' in this section, which is not a label
+                            break
+                        };
+                        // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
+                        if (c.is_alphabetic() || matches!(c, '.' | '_'))
+                            && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
+                        {
+                            found_labels.push(possible_label);
+                        } else {
+                            // If we encounter a non-label, there cannot be any further labels, so stop checking
                             break;
                         }
 

compiler/rustc_lint/src/levels.rs

@@ -227,14 +227,12 @@ impl<'s> LintLevelsBuilder<'s> {
         let sess = self.sess;
         let bad_attr = |span| struct_span_err!(sess, span, E0452, "malformed lint attribute input");
         for attr in attrs {
-            let level = match Level::from_symbol(attr.name_or_empty()) {
-                None => continue,
-                Some(lvl) => lvl,
+            let Some(level) = Level::from_symbol(attr.name_or_empty()) else {
+                continue
             };
 
-            let mut metas = match attr.meta_item_list() {
-                Some(x) => x,
-                None => continue,
+            let Some(mut metas) = attr.meta_item_list() else {
+                continue
             };
 
             if metas.is_empty() {
@@ -481,9 +479,8 @@ impl<'s> LintLevelsBuilder<'s> {
                     continue;
                 }
 
-                let (lint_attr_name, lint_attr_span) = match *src {
-                    LintLevelSource::Node(name, span, _) => (name, span),
-                    _ => continue,
+                let LintLevelSource::Node(lint_attr_name, lint_attr_span, _) = *src else {
+                    continue
                 };
 
                 let lint = builtin::UNUSED_ATTRIBUTES;

compiler/rustc_lint/src/noop_method_call.rs

@@ -40,9 +40,8 @@ declare_lint_pass!(NoopMethodCall => [NOOP_METHOD_CALL]);
 impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         // We only care about method calls.
-        let (call, elements) = match expr.kind {
-            ExprKind::MethodCall(call, _, elements, _) => (call, elements),
-            _ => return,
+        let ExprKind::MethodCall(call, _, elements, _) = &expr.kind else {
+            return
         };
         // We only care about method calls corresponding to the `Clone`, `Deref` and `Borrow`
         // traits and ignore any other method call.
@@ -70,9 +69,8 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
         }
         let param_env = cx.tcx.param_env(trait_id);
         // Resolve the trait method instance.
-        let i = match ty::Instance::resolve(cx.tcx, param_env, did, substs) {
-            Ok(Some(i)) => i,
-            _ => return,
+        let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, param_env, did, substs) else {
+            return
         };
         // (Re)check that it implements the noop diagnostic.
         let Some(name) = cx.tcx.get_diagnostic_name(i.def_id()) else { return };

compiler/rustc_lint/src/traits.rs

@@ -91,9 +91,8 @@ impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
 
         let predicates = cx.tcx.explicit_predicates_of(item.def_id);
         for &(predicate, span) in predicates.predicates {
-            let trait_predicate = match predicate.kind().skip_binder() {
-                Trait(trait_predicate) => trait_predicate,
-                _ => continue,
+            let Trait(trait_predicate) = predicate.kind().skip_binder() else {
+                continue
             };
             if trait_predicate.constness == ty::BoundConstness::ConstIfConst {
                 // `~const Drop` definitely have meanings so avoid linting here.
@@ -106,9 +105,8 @@ impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
                     continue;
                 }
                 cx.struct_span_lint(DROP_BOUNDS, span, |lint| {
-                    let needs_drop = match cx.tcx.get_diagnostic_item(sym::needs_drop) {
-                        Some(needs_drop) => needs_drop,
-                        None => return,
+                    let Some(needs_drop) = cx.tcx.get_diagnostic_item(sym::needs_drop) else {
+                        return
                     };
                     let msg = format!(
                         "bounds on `{}` are most likely incorrect, consider instead \
@@ -123,17 +121,15 @@ impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
     }
 
     fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx hir::Ty<'tcx>) {
-        let bounds = match &ty.kind {
-            hir::TyKind::TraitObject(bounds, _lifetime, _syntax) => bounds,
-            _ => return,
+        let hir::TyKind::TraitObject(bounds, _lifetime, _syntax) = &ty.kind else {
+            return
         };
         for bound in &bounds[..] {
             let def_id = bound.trait_ref.trait_def_id();
             if cx.tcx.lang_items().drop_trait() == def_id {
                 cx.struct_span_lint(DYN_DROP, bound.span, |lint| {
-                    let needs_drop = match cx.tcx.get_diagnostic_item(sym::needs_drop) {
-                        Some(needs_drop) => needs_drop,
-                        None => return,
+                    let Some(needs_drop) = cx.tcx.get_diagnostic_item(sym::needs_drop) else {
+                        return
                     };
                     let msg = format!(
                         "types that do not implement `Drop` can still have drop glue, consider \

compiler/rustc_lint/src/types.rs

@@ -1342,11 +1342,10 @@ impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
                     | ty::layout::LayoutError::NormalizationFailure(_, _),
                 ) => return,
             };
-            let (variants, tag) = match layout.variants {
-                Variants::Multiple {
+            let Variants::Multiple {
                     tag_encoding: TagEncoding::Direct, tag, ref variants, ..
-                } => (variants, tag),
-                _ => return,
+                } = &layout.variants else {
+                return
             };
 
             let tag_size = tag.value.size(&cx.tcx).bytes();

compiler/rustc_middle/src/ty/adt.rs

@@ -64,6 +64,30 @@ bitflags! {
 /// Moreover, Rust only allows recursive data types through indirection.
 ///
 /// [adt]: https://en.wikipedia.org/wiki/Algebraic_data_type
+///
+/// # Recursive types
+///
+/// It may seem impossible to represent recursive types using [`Ty`],
+/// since [`TyKind::Adt`] includes [`AdtDef`], which includes its fields,
+/// creating a cycle. However, `AdtDef` does not actually include the *types*
+/// of its fields; it includes just their [`DefId`]s.
+///
+/// [`TyKind::Adt`]: ty::TyKind::Adt
+///
+/// For example, the following type:
+///
+/// ```
+/// struct S { x: Box<S> }
+/// ```
+///
+/// is essentially represented with [`Ty`] as the following pseudocode:
+///
+/// ```
+/// struct S { x }
+/// ```
+///
+/// where `x` here represents the `DefId` of `S.x`. Then, the `DefId`
+/// can be used with [`TyCtxt::type_of()`] to get the type of the field.
 pub struct AdtDef {
     /// The `DefId` of the struct, enum or union item.
     pub did: DefId,

compiler/rustc_middle/src/ty/mod.rs

@@ -1711,7 +1711,7 @@ impl ReprOptions {
 
 impl<'tcx> FieldDef {
     /// Returns the type of this field. The resulting type is not normalized. The `subst` is
-    /// typically obtained via the second field of `TyKind::AdtDef`.
+    /// typically obtained via the second field of [`TyKind::Adt`].
     pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
         tcx.type_of(self.did).subst(tcx, subst)
     }

compiler/rustc_typeck/src/check/demand.rs

@@ -1223,7 +1223,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // Missing try_into implementation for `{integer}` to `{float}`
                     err.multipart_suggestion_verbose(
                         &format!(
-                            "{}, producing the floating point representation of the integer,
+                            "{}, producing the floating point representation of the integer, \
                                  rounded if necessary",
                             cast_msg,
                         ),