Rollup of 7 pull requests

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -813,17 +813,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             if *outlived_f != ty::ReStatic {
                 return;
             }
+            let suitable_region = self.infcx.tcx.is_suitable_region(f);
+            let Some(suitable_region) = suitable_region else { return; };
 
-            let fn_returns = self
-                .infcx
-                .tcx
-                .is_suitable_region(f)
-                .map(|r| self.infcx.tcx.return_type_impl_or_dyn_traits(r.def_id))
-                .unwrap_or_default();
-
-            if fn_returns.is_empty() {
-                return;
-            }
+            let fn_returns = self.infcx.tcx.return_type_impl_or_dyn_traits(suitable_region.def_id);
 
             let param = if let Some(param) = find_param_with_region(self.infcx.tcx, f, outlived_f) {
                 param
@@ -839,15 +832,43 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             };
             let captures = format!("captures data from {arg}");
 
-            return nice_region_error::suggest_new_region_bound(
-                self.infcx.tcx,
-                diag,
-                fn_returns,
-                lifetime.to_string(),
-                Some(arg),
-                captures,
-                Some((param.param_ty_span, param.param_ty.to_string())),
-                self.infcx.tcx.is_suitable_region(f).map(|r| r.def_id),
+            if !fn_returns.is_empty() {
+                nice_region_error::suggest_new_region_bound(
+                    self.infcx.tcx,
+                    diag,
+                    fn_returns,
+                    lifetime.to_string(),
+                    Some(arg),
+                    captures,
+                    Some((param.param_ty_span, param.param_ty.to_string())),
+                    Some(suitable_region.def_id),
+                );
+                return;
+            }
+
+            let Some((alias_tys, alias_span)) = self
+                .infcx
+                .tcx
+                .return_type_impl_or_dyn_traits_with_type_alias(suitable_region.def_id) else { return; };
+
+            // in case the return type of the method is a type alias
+            let mut spans_suggs: Vec<_> = Vec::new();
+            for alias_ty in alias_tys {
+                if alias_ty.span.desugaring_kind().is_some() {
+                    // Skip `async` desugaring `impl Future`.
+                    ()
+                }
+                if let TyKind::TraitObject(_, lt, _) = alias_ty.kind {
+                    spans_suggs.push((lt.ident.span.shrink_to_hi(), " + 'a".to_string()));
+                }
+            }
+            spans_suggs.push((alias_span.shrink_to_hi(), "<'a>".to_string()));
+            diag.multipart_suggestion_verbose(
+                &format!(
+                    "to declare that the trait object {captures}, you can add a lifetime parameter `'a` in the type alias"
+                ),
+                spans_suggs,
+                Applicability::MaybeIncorrect,
             );
         }
     }

compiler/rustc_error_messages/locales/en-US/parse.ftl

@@ -238,6 +238,7 @@ parse_const_let_mutually_exclusive = `const` and `let` are mutually exclusive
 
 parse_invalid_expression_in_let_else = a `{$operator}` expression cannot be directly assigned in `let...else`
 parse_invalid_curly_in_let_else = right curly brace `{"}"}` before `else` in a `let...else` statement not allowed
+parse_extra_if_in_let_else = remove the `if` if you meant to write a `let...else` statement
 
 parse_compound_assignment_expression_in_let = can't reassign to an uninitialized variable
     .suggestion = initialize the variable

compiler/rustc_hir/src/hir.rs

@@ -3524,6 +3524,13 @@ impl<'hir> Node<'hir> {
         }
     }
 
+    pub fn alias_ty(self) -> Option<&'hir Ty<'hir>> {
+        match self {
+            Node::Item(Item { kind: ItemKind::TyAlias(ty, ..), .. }) => Some(ty),
+            _ => None,
+        }
+    }
+
     pub fn body_id(&self) -> Option<BodyId> {
         match self {
             Node::TraitItem(TraitItem {

compiler/rustc_hir_typeck/src/coercion.rs

@@ -1619,6 +1619,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
             }
         }
     }
+
     fn note_unreachable_loop_return(
         &self,
         err: &mut Diagnostic,

compiler/rustc_hir_typeck/src/demand.rs

@@ -59,7 +59,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
             || self.suggest_clone_for_ref(err, expr, expr_ty, expected)
             || self.suggest_into(err, expr, expr_ty, expected)
-            || self.suggest_floating_point_literal(err, expr, expected);
+            || self.suggest_floating_point_literal(err, expr, expected)
+            || self.note_result_coercion(err, expr, expected, expr_ty);
         if !suggested {
             self.point_at_expr_source_of_inferred_type(err, expr, expr_ty, expected);
         }
@@ -697,6 +698,56 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         );
     }
 
+    pub(crate) fn note_result_coercion(
+        &self,
+        err: &mut Diagnostic,
+        expr: &hir::Expr<'tcx>,
+        expected: Ty<'tcx>,
+        found: Ty<'tcx>,
+    ) -> bool {
+        let ty::Adt(e, substs_e) = expected.kind() else { return false; };
+        let ty::Adt(f, substs_f) = found.kind() else { return false; };
+        if e.did() != f.did() {
+            return false;
+        }
+        if Some(e.did()) != self.tcx.get_diagnostic_item(sym::Result) {
+            return false;
+        }
+        let map = self.tcx.hir();
+        if let Some(hir::Node::Expr(expr)) = map.find_parent(expr.hir_id)
+            && let hir::ExprKind::Ret(_) = expr.kind
+        {
+            // `return foo;`
+        } else if map.get_return_block(expr.hir_id).is_some() {
+            // Function's tail expression.
+        } else {
+            return false;
+        }
+        let e = substs_e.type_at(1);
+        let f = substs_f.type_at(1);
+        if self
+            .infcx
+            .type_implements_trait(
+                self.tcx.get_diagnostic_item(sym::Into).unwrap(),
+                [f, e],
+                self.param_env,
+            )
+            .must_apply_modulo_regions()
+        {
+            err.multipart_suggestion(
+                "use `?` to coerce and return an appropriate `Err`, and wrap the resulting value \
+                 in `Ok` so the expression remains of type `Result`",
+                vec![
+                    (expr.span.shrink_to_lo(), "Ok(".to_string()),
+                    (expr.span.shrink_to_hi(), "?)".to_string()),
+                ],
+                Applicability::MaybeIncorrect,
+            );
+            return true;
+        }
+        false
+    }
+
     /// If the expected type is an enum (Issue #55250) with any variants whose
     /// sole field is of the found type, suggest such variants. (Issue #42764)
     fn suggest_compatible_variants(

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -985,7 +985,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
         let vis = self.get_visibility(id);
         let span = self.get_span(id, sess);
         let macro_rules = match kind {
-            DefKind::Macro(..) => self.root.tables.macro_rules.get(self, id).is_some(),
+            DefKind::Macro(..) => self.root.tables.is_macro_rules.get(self, id),
             _ => false,
         };
 
@@ -1283,7 +1283,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     fn get_macro(self, id: DefIndex, sess: &Session) -> ast::MacroDef {
         match self.def_kind(id) {
             DefKind::Macro(_) => {
-                let macro_rules = self.root.tables.macro_rules.get(self, id).is_some();
+                let macro_rules = self.root.tables.is_macro_rules.get(self, id);
                 let body =
                     self.root.tables.macro_definition.get(self, id).unwrap().decode((self, sess));
                 ast::MacroDef { macro_rules, body: ast::ptr::P(body) }
@@ -1595,11 +1595,11 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     }
 
     fn get_attr_flags(self, index: DefIndex) -> AttrFlags {
-        self.root.tables.attr_flags.get(self, index).unwrap_or(AttrFlags::empty())
+        self.root.tables.attr_flags.get(self, index)
     }
 
     fn get_is_intrinsic(self, index: DefIndex) -> bool {
-        self.root.tables.is_intrinsic.get(self, index).is_some()
+        self.root.tables.is_intrinsic.get(self, index)
     }
 }
 

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -226,12 +226,7 @@ provide! { tcx, def_id, other, cdata,
     deduced_param_attrs => { table }
     is_type_alias_impl_trait => {
         debug_assert_eq!(tcx.def_kind(def_id), DefKind::OpaqueTy);
-        cdata
-            .root
-            .tables
-            .is_type_alias_impl_trait
-            .get(cdata, def_id.index)
-            .is_some()
+        cdata.root.tables.is_type_alias_impl_trait.get(cdata, def_id.index)
     }
     collect_return_position_impl_trait_in_trait_tys => {
         Ok(cdata

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -483,7 +483,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         self.lazy(DefPathHashMapRef::BorrowedFromTcx(self.tcx.def_path_hash_to_def_index_map()))
     }
 
-    fn encode_source_map(&mut self) -> LazyTable<u32, LazyValue<rustc_span::SourceFile>> {
+    fn encode_source_map(&mut self) -> LazyTable<u32, Option<LazyValue<rustc_span::SourceFile>>> {
         let source_map = self.tcx.sess.source_map();
         let all_source_files = source_map.files();
 
@@ -1130,7 +1130,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             attr_flags |= AttrFlags::IS_DOC_HIDDEN;
         }
         if !attr_flags.is_empty() {
-            self.tables.attr_flags.set(def_id.local_def_index, attr_flags);
+            self.tables.attr_flags.set_nullable(def_id.local_def_index, attr_flags);
         }
     }
 
@@ -1387,7 +1387,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         if impl_item.kind == ty::AssocKind::Fn {
             record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
             if tcx.is_intrinsic(def_id) {
-                self.tables.is_intrinsic.set(def_id.index, ());
+                self.tables.is_intrinsic.set_nullable(def_id.index, true);
             }
         }
     }
@@ -1519,7 +1519,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
             hir::ItemKind::Macro(ref macro_def, _) => {
                 if macro_def.macro_rules {
-                    self.tables.macro_rules.set(def_id.index, ());
+                    self.tables.is_macro_rules.set_nullable(def_id.index, true);
                 }
                 record!(self.tables.macro_definition[def_id] <- &*macro_def.body);
             }
@@ -1529,7 +1529,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             hir::ItemKind::OpaqueTy(ref opaque) => {
                 self.encode_explicit_item_bounds(def_id);
                 if matches!(opaque.origin, hir::OpaqueTyOrigin::TyAlias) {
-                    self.tables.is_type_alias_impl_trait.set(def_id.index, ());
+                    self.tables.is_type_alias_impl_trait.set_nullable(def_id.index, true);
                 }
             }
             hir::ItemKind::Enum(..) => {
@@ -1636,7 +1636,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         if let hir::ItemKind::Fn(..) = item.kind {
             record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
             if tcx.is_intrinsic(def_id) {
-                self.tables.is_intrinsic.set(def_id.index, ());
+                self.tables.is_intrinsic.set_nullable(def_id.index, true);
             }
         }
         if let hir::ItemKind::Impl { .. } = item.kind {
@@ -2038,7 +2038,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         }
         if let hir::ForeignItemKind::Fn(..) = nitem.kind {
             if tcx.is_intrinsic(def_id) {
-                self.tables.is_intrinsic.set(def_id.index, ());
+                self.tables.is_intrinsic.set_nullable(def_id.index, true);
             }
         }
     }

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -185,9 +185,9 @@ enum LazyState {
     Previous(NonZeroUsize),
 }
 
-type SyntaxContextTable = LazyTable<u32, LazyValue<SyntaxContextData>>;
-type ExpnDataTable = LazyTable<ExpnIndex, LazyValue<ExpnData>>;
-type ExpnHashTable = LazyTable<ExpnIndex, LazyValue<ExpnHash>>;
+type SyntaxContextTable = LazyTable<u32, Option<LazyValue<SyntaxContextData>>>;
+type ExpnDataTable = LazyTable<ExpnIndex, Option<LazyValue<ExpnData>>>;
+type ExpnHashTable = LazyTable<ExpnIndex, Option<LazyValue<ExpnHash>>>;
 
 #[derive(MetadataEncodable, MetadataDecodable)]
 pub(crate) struct ProcMacroData {
@@ -253,7 +253,7 @@ pub(crate) struct CrateRoot {
 
     def_path_hash_map: LazyValue<DefPathHashMapRef<'static>>,
 
-    source_map: LazyTable<u32, LazyValue<rustc_span::SourceFile>>,
+    source_map: LazyTable<u32, Option<LazyValue<rustc_span::SourceFile>>>,
 
     compiler_builtins: bool,
     needs_allocator: bool,
@@ -315,31 +315,43 @@ pub(crate) struct IncoherentImpls {
 
 /// Define `LazyTables` and `TableBuilders` at the same time.
 macro_rules! define_tables {
-    ($($name:ident: Table<$IDX:ty, $T:ty>),+ $(,)?) => {
+    (
+        - nullable: $($name1:ident: Table<$IDX1:ty, $T1:ty>,)+
+        - optional: $($name2:ident: Table<$IDX2:ty, $T2:ty>,)+
+    ) => {
         #[derive(MetadataEncodable, MetadataDecodable)]
         pub(crate) struct LazyTables {
-            $($name: LazyTable<$IDX, $T>),+
+            $($name1: LazyTable<$IDX1, $T1>,)+
+            $($name2: LazyTable<$IDX2, Option<$T2>>,)+
         }
 
         #[derive(Default)]
         struct TableBuilders {
-            $($name: TableBuilder<$IDX, $T>),+
+            $($name1: TableBuilder<$IDX1, $T1>,)+
+            $($name2: TableBuilder<$IDX2, Option<$T2>>,)+
         }
 
         impl TableBuilders {
             fn encode(&self, buf: &mut FileEncoder) -> LazyTables {
                 LazyTables {
-                    $($name: self.$name.encode(buf)),+
+                    $($name1: self.$name1.encode(buf),)+
+                    $($name2: self.$name2.encode(buf),)+
                 }
             }
         }
     }
 }
 
 define_tables! {
+- nullable:
+    is_intrinsic: Table<DefIndex, bool>,
+    is_macro_rules: Table<DefIndex, bool>,
+    is_type_alias_impl_trait: Table<DefIndex, bool>,
+    attr_flags: Table<DefIndex, AttrFlags>,
+
+- optional:
     attributes: Table<DefIndex, LazyArray<ast::Attribute>>,
     children: Table<DefIndex, LazyArray<DefIndex>>,
-
     opt_def_kind: Table<DefIndex, DefKind>,
     visibility: Table<DefIndex, LazyValue<ty::Visibility<DefIndex>>>,
     def_span: Table<DefIndex, LazyValue<Span>>,
@@ -370,7 +382,6 @@ define_tables! {
     impl_parent: Table<DefIndex, RawDefId>,
     impl_polarity: Table<DefIndex, ty::ImplPolarity>,
     constness: Table<DefIndex, hir::Constness>,
-    is_intrinsic: Table<DefIndex, ()>,
     impl_defaultness: Table<DefIndex, hir::Defaultness>,
     // FIXME(eddyb) perhaps compute this on the fly if cheap enough?
     coerce_unsized_info: Table<DefIndex, LazyValue<ty::adjustment::CoerceUnsizedInfo>>,
@@ -380,7 +391,6 @@ define_tables! {
     fn_arg_names: Table<DefIndex, LazyArray<Ident>>,
     generator_kind: Table<DefIndex, LazyValue<hir::GeneratorKind>>,
     trait_def: Table<DefIndex, LazyValue<ty::TraitDef>>,
-
     trait_item_def_id: Table<DefIndex, RawDefId>,
     inherent_impls: Table<DefIndex, LazyArray<DefIndex>>,
     expn_that_defined: Table<DefIndex, LazyValue<ExpnId>>,
@@ -395,18 +405,12 @@ define_tables! {
     def_path_hashes: Table<DefIndex, DefPathHash>,
     proc_macro_quoted_spans: Table<usize, LazyValue<Span>>,
     generator_diagnostic_data: Table<DefIndex, LazyValue<GeneratorDiagnosticData<'static>>>,
-    attr_flags: Table<DefIndex, AttrFlags>,
     variant_data: Table<DefIndex, LazyValue<VariantData>>,
     assoc_container: Table<DefIndex, ty::AssocItemContainer>,
-    // Slot is full when macro is macro_rules.
-    macro_rules: Table<DefIndex, ()>,
     macro_definition: Table<DefIndex, LazyValue<ast::DelimArgs>>,
     proc_macro: Table<DefIndex, MacroKind>,
     module_reexports: Table<DefIndex, LazyArray<ModChild>>,
     deduced_param_attrs: Table<DefIndex, LazyArray<DeducedParamAttrs>>,
-    // Slot is full when opaque is TAIT.
-    is_type_alias_impl_trait: Table<DefIndex, ()>,
-
     trait_impl_trait_tys: Table<DefIndex, LazyValue<FxHashMap<DefId, Ty<'static>>>>,
 }
 
@@ -419,6 +423,7 @@ struct VariantData {
 }
 
 bitflags::bitflags! {
+    #[derive(Default)]
     pub struct AttrFlags: u8 {
         const MAY_HAVE_DOC_LINKS = 1 << 0;
         const IS_DOC_HIDDEN      = 1 << 1;