Rollup of 7 pull requests

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -845,7 +845,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 return;
             }
 
-            let Some((alias_tys, alias_span)) = self
+            let Some((alias_tys, alias_span, lt_addition_span)) = self
                 .infcx
                 .tcx
                 .return_type_impl_or_dyn_traits_with_type_alias(suitable_region.def_id) else { return; };
@@ -858,10 +858,20 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     ()
                 }
                 if let TyKind::TraitObject(_, lt, _) = alias_ty.kind {
-                    spans_suggs.push((lt.ident.span.shrink_to_hi(), " + 'a".to_string()));
+                    if lt.ident.name == kw::Empty {
+                        spans_suggs.push((lt.ident.span.shrink_to_hi(), " + 'a".to_string()));
+                    } else {
+                        spans_suggs.push((lt.ident.span, "'a".to_string()));
+                    }
                 }
             }
-            spans_suggs.push((alias_span.shrink_to_hi(), "<'a>".to_string()));
+
+            if let Some(lt_addition_span) = lt_addition_span {
+                spans_suggs.push((lt_addition_span, "'a, ".to_string()));
+            } else {
+                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"

compiler/rustc_codegen_cranelift/src/common.rs

@@ -361,7 +361,7 @@ impl<'tcx> FunctionCx<'_, '_, 'tcx> {
         self.instance.subst_mir_and_normalize_erasing_regions(
             self.tcx,
             ty::ParamEnv::reveal_all(),
-            value,
+            ty::EarlyBinder(value),
         )
     }
 

compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs

@@ -93,7 +93,7 @@ fn make_mir_scope<'ll, 'tcx>(
             let callee = cx.tcx.subst_and_normalize_erasing_regions(
                 instance.substs,
                 ty::ParamEnv::reveal_all(),
-                callee,
+                ty::EarlyBinder(callee),
             );
             let callee_fn_abi = cx.fn_abi_of_instance(callee, ty::List::empty());
             cx.dbg_scope_fn(callee, callee_fn_abi, None)

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -529,7 +529,7 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     let impl_self_ty = cx.tcx.subst_and_normalize_erasing_regions(
                         instance.substs,
                         ty::ParamEnv::reveal_all(),
-                        cx.tcx.type_of(impl_def_id).skip_binder(),
+                        cx.tcx.type_of(impl_def_id),
                     );
 
                     // Only "class" methods are generally understood by LLVM,

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -111,7 +111,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         self.instance.subst_mir_and_normalize_erasing_regions(
             self.cx.tcx(),
             ty::ParamEnv::reveal_all(),
-            value,
+            ty::EarlyBinder(value),
         )
     }
 }

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -495,7 +495,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     ) -> Result<T, InterpError<'tcx>> {
         frame
             .instance
-            .try_subst_mir_and_normalize_erasing_regions(*self.tcx, self.param_env, value)
+            .try_subst_mir_and_normalize_erasing_regions(
+                *self.tcx,
+                self.param_env,
+                ty::EarlyBinder(value),
+            )
             .map_err(|_| err_inval!(TooGeneric))
     }
 

compiler/rustc_data_structures/src/profiling.rs

@@ -101,7 +101,7 @@ use parking_lot::RwLock;
 use smallvec::SmallVec;
 
 bitflags::bitflags! {
-    struct EventFilter: u32 {
+    struct EventFilter: u16 {
         const GENERIC_ACTIVITIES  = 1 << 0;
         const QUERY_PROVIDERS     = 1 << 1;
         const QUERY_CACHE_HITS    = 1 << 2;

compiler/rustc_hir_typeck/messages.ftl

@@ -75,3 +75,7 @@ hir_typeck_union_pat_dotdot = `..` cannot be used in union patterns
 
 hir_typeck_arg_mismatch_indeterminate = argument type mismatch was detected, but rustc had trouble determining where
     .note = we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new
+
+hir_typeck_suggest_boxing_note = for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
+
+hir_typeck_suggest_boxing_when_appropriate = store this in the heap by calling `Box::new`

compiler/rustc_hir_typeck/src/demand.rs

@@ -51,7 +51,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             || self.suggest_non_zero_new_unwrap(err, expr, expected, expr_ty)
             || self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty)
             || self.suggest_no_capture_closure(err, expected, expr_ty)
-            || self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty)
+            || self.suggest_boxing_when_appropriate(err, expr.span, expr.hir_id, expected, expr_ty)
             || self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
             || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
             || self.suggest_clone_for_ref(err, expr, expr_ty, expected)

compiler/rustc_hir_typeck/src/errors.rs

@@ -267,3 +267,31 @@ pub struct ArgMismatchIndeterminate {
     #[primary_span]
     pub span: Span,
 }
+
+#[derive(Subdiagnostic)]
+pub enum SuggestBoxing {
+    #[note(hir_typeck_suggest_boxing_note)]
+    #[multipart_suggestion(
+        hir_typeck_suggest_boxing_when_appropriate,
+        applicability = "machine-applicable"
+    )]
+    Unit {
+        #[suggestion_part(code = "Box::new(())")]
+        start: Span,
+        #[suggestion_part(code = "")]
+        end: Span,
+    },
+    #[note(hir_typeck_suggest_boxing_note)]
+    AsyncBody,
+    #[note(hir_typeck_suggest_boxing_note)]
+    #[multipart_suggestion(
+        hir_typeck_suggest_boxing_when_appropriate,
+        applicability = "machine-applicable"
+    )]
+    Other {
+        #[suggestion_part(code = "Box::new(")]
+        start: Span,
+        #[suggestion_part(code = ")")]
+        end: Span,
+    },
+}

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1519,7 +1519,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // case we can ignore the tail expression (e.g., `'a: {
         // break 'a 22; }` would not force the type of the block
         // to be `()`).
-        let tail_expr = blk.expr.as_ref();
         let coerce_to_ty = expected.coercion_target_type(self, blk.span);
         let coerce = if blk.targeted_by_break {
             CoerceMany::new(coerce_to_ty)
@@ -1537,13 +1536,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // check the tail expression **without** holding the
             // `enclosing_breakables` lock below.
-            let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
+            let tail_expr_ty =
+                blk.expr.map(|expr| (expr, self.check_expr_with_expectation(expr, expected)));
 
             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
             let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
             let coerce = ctxt.coerce.as_mut().unwrap();
-            if let Some(tail_expr_ty) = tail_expr_ty {
-                let tail_expr = tail_expr.unwrap();
+            if let Some((tail_expr, tail_expr_ty)) = tail_expr_ty {
                 let span = self.get_expr_coercion_span(tail_expr);
                 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
                 let ty_for_diagnostic = coerce.merged_ty();
@@ -1596,6 +1595,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         &self.misc(sp),
                         &mut |err| {
                             if let Some(expected_ty) = expected.only_has_type(self) {
+                                if blk.stmts.is_empty() && blk.expr.is_none() {
+                                    self.suggest_boxing_when_appropriate(
+                                        err,
+                                        blk.span,
+                                        blk.hir_id,
+                                        expected_ty,
+                                        self.tcx.mk_unit(),
+                                    );
+                                }
                                 if !self.consider_removing_semicolon(blk, expected_ty, err) {
                                     self.err_ctxt().consider_returning_binding(
                                         blk,
@@ -1608,7 +1616,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     // silence this redundant error, as we already emit E0070.
 
                                     // Our block must be a `assign desugar local; assignment`
-                                    if let Some(hir::Node::Block(hir::Block {
+                                    if let hir::Block {
                                         stmts:
                                             [
                                                 hir::Stmt {
@@ -1630,7 +1638,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                                 },
                                             ],
                                         ..
-                                    })) = self.tcx.hir().find(blk.hir_id)
+                                    } = blk
                                     {
                                         self.comes_from_while_condition(blk.hir_id, |_| {
                                             err.downgrade_to_delayed_bug();

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1,6 +1,6 @@
 use super::FnCtxt;
 
-use crate::errors::{AddReturnTypeSuggestion, ExpectedReturnTypeLabel};
+use crate::errors::{AddReturnTypeSuggestion, ExpectedReturnTypeLabel, SuggestBoxing};
 use crate::fluent_generated as fluent;
 use crate::method::probe::{IsSuggestion, Mode, ProbeScope};
 use rustc_ast::util::parser::{ExprPrecedence, PREC_POSTFIX};
@@ -9,7 +9,8 @@ use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
-    Expr, ExprKind, GenericBound, Node, Path, QPath, Stmt, StmtKind, TyKind, WherePredicate,
+    AsyncGeneratorKind, Expr, ExprKind, GeneratorKind, GenericBound, HirId, Node, Path, QPath,
+    Stmt, StmtKind, TyKind, WherePredicate,
 };
 use rustc_hir_analysis::astconv::AstConv;
 use rustc_infer::traits::{self, StatementAsExpression};
@@ -438,33 +439,32 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(in super::super) fn suggest_boxing_when_appropriate(
         &self,
         err: &mut Diagnostic,
-        expr: &hir::Expr<'_>,
+        span: Span,
+        hir_id: HirId,
         expected: Ty<'tcx>,
         found: Ty<'tcx>,
     ) -> bool {
-        if self.tcx.hir().is_inside_const_context(expr.hir_id) {
-            // Do not suggest `Box::new` in const context.
-            return false;
-        }
-        if !expected.is_box() || found.is_box() {
+        // Do not suggest `Box::new` in const context.
+        if self.tcx.hir().is_inside_const_context(hir_id) || !expected.is_box() || found.is_box() {
             return false;
         }
-        let boxed_found = self.tcx.mk_box(found);
-        if self.can_coerce(boxed_found, expected) {
-            err.multipart_suggestion(
-                "store this in the heap by calling `Box::new`",
-                vec![
-                    (expr.span.shrink_to_lo(), "Box::new(".to_string()),
-                    (expr.span.shrink_to_hi(), ")".to_string()),
-                ],
-                Applicability::MachineApplicable,
-            );
-            err.note(
-                "for more on the distinction between the stack and the heap, read \
-                 https://doc.rust-lang.org/book/ch15-01-box.html, \
-                 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
-                 https://doc.rust-lang.org/std/boxed/index.html",
-            );
+        if self.can_coerce(self.tcx.mk_box(found), expected) {
+            let suggest_boxing = match found.kind() {
+                ty::Tuple(tuple) if tuple.is_empty() => {
+                    SuggestBoxing::Unit { start: span.shrink_to_lo(), end: span }
+                }
+                ty::Generator(def_id, ..)
+                    if matches!(
+                        self.tcx.generator_kind(def_id),
+                        Some(GeneratorKind::Async(AsyncGeneratorKind::Closure))
+                    ) =>
+                {
+                    SuggestBoxing::AsyncBody
+                }
+                _ => SuggestBoxing::Other { start: span.shrink_to_lo(), end: span.shrink_to_hi() },
+            };
+            err.subdiagnostic(suggest_boxing);
+
             true
         } else {
             false

compiler/rustc_middle/src/ty/adt.rs

@@ -26,7 +26,7 @@ use super::{Destructor, FieldDef, GenericPredicates, Ty, TyCtxt, VariantDef, Var
 
 bitflags! {
     #[derive(HashStable, TyEncodable, TyDecodable)]
-    pub struct AdtFlags: u32 {
+    pub struct AdtFlags: u16 {
         const NO_ADT_FLAGS        = 0;
         /// Indicates whether the ADT is an enum.
         const IS_ENUM             = 1 << 0;

compiler/rustc_middle/src/ty/context.rs

@@ -1093,11 +1093,13 @@ impl<'tcx> TyCtxt<'tcx> {
         v.0
     }
 
-    /// Given a `DefId` for an `fn`, return all the `dyn` and `impl` traits in its return type and associated alias span when type alias is used
+    /// Given a `DefId` for an `fn`, return all the `dyn` and `impl` traits in
+    /// its return type, and the associated alias span when type alias is used,
+    /// along with a span for lifetime suggestion (if there are existing generics).
     pub fn return_type_impl_or_dyn_traits_with_type_alias(
         self,
         scope_def_id: LocalDefId,
-    ) -> Option<(Vec<&'tcx hir::Ty<'tcx>>, Span)> {
+    ) -> Option<(Vec<&'tcx hir::Ty<'tcx>>, Span, Option<Span>)> {
         let hir_id = self.hir().local_def_id_to_hir_id(scope_def_id);
         let mut v = TraitObjectVisitor(vec![], self.hir());
         // when the return type is a type alias
@@ -1111,7 +1113,7 @@ impl<'tcx> TyCtxt<'tcx> {
         {
             v.visit_ty(alias_ty);
             if !v.0.is_empty() {
-                return Some((v.0, alias_generics.span));
+                return Some((v.0, alias_generics.span, alias_generics.span_for_lifetime_suggestion()));
             }
         }
         return None;

compiler/rustc_middle/src/ty/instance.rs

@@ -115,7 +115,7 @@ impl<'tcx> Instance<'tcx> {
     /// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
     pub fn ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
         let ty = tcx.type_of(self.def.def_id());
-        tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty.skip_binder())
+        tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty)
     }
 
     /// Finds a crate that contains a monomorphization of this instance that
@@ -578,14 +578,15 @@ impl<'tcx> Instance<'tcx> {
         self.def.has_polymorphic_mir_body().then_some(self.substs)
     }
 
-    pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T
+    pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: EarlyBinder<&T>) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>> + Copy,
     {
+        let v = v.map_bound(|v| *v);
         if let Some(substs) = self.substs_for_mir_body() {
-            EarlyBinder(*v).subst(tcx, substs)
+            v.subst(tcx, substs)
         } else {
-            *v
+            v.skip_binder()
         }
     }
 
@@ -594,15 +595,15 @@ impl<'tcx> Instance<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        v: T,
+        v: EarlyBinder<T>,
     ) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>> + Clone,
     {
         if let Some(substs) = self.substs_for_mir_body() {
             tcx.subst_and_normalize_erasing_regions(substs, param_env, v)
         } else {
-            tcx.normalize_erasing_regions(param_env, v)
+            tcx.normalize_erasing_regions(param_env, v.skip_binder())
         }
     }
 
@@ -611,15 +612,15 @@ impl<'tcx> Instance<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        v: T,
+        v: EarlyBinder<T>,
     ) -> Result<T, NormalizationError<'tcx>>
     where
         T: TypeFoldable<TyCtxt<'tcx>> + Clone,
     {
         if let Some(substs) = self.substs_for_mir_body() {
             tcx.try_subst_and_normalize_erasing_regions(substs, param_env, v)
         } else {
-            tcx.try_normalize_erasing_regions(param_env, v)
+            tcx.try_normalize_erasing_regions(param_env, v.skip_binder())
         }
     }
 

compiler/rustc_middle/src/ty/mod.rs

@@ -1739,7 +1739,7 @@ pub struct Destructor {
 
 bitflags! {
     #[derive(HashStable, TyEncodable, TyDecodable)]
-    pub struct VariantFlags: u32 {
+    pub struct VariantFlags: u8 {
         const NO_VARIANT_FLAGS        = 0;
         /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
         const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0;