Rollup of 6 pull requests

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -698,7 +698,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                                     ),
                                 ..
                             }) => {
-                                let hir::Ty { span, .. } = inputs[local.index() - 1];
+                                let hir::Ty { span, .. } = *inputs.get(local.index() - 1)?;
                                 Some(span)
                             }
                             _ => None,

compiler/rustc_const_eval/messages.ftl

@@ -453,7 +453,7 @@ const_eval_validation_invalid_fn_ptr = {$front_matter}: encountered {$value}, bu
 const_eval_validation_invalid_ref_meta = {$front_matter}: encountered invalid reference metadata: total size is bigger than largest supported object
 const_eval_validation_invalid_ref_slice_meta = {$front_matter}: encountered invalid reference metadata: slice is bigger than largest supported object
 const_eval_validation_invalid_vtable_ptr = {$front_matter}: encountered {$value}, but expected a vtable pointer
-const_eval_validation_mutable_ref_in_const = {$front_matter}: encountered mutable reference in a `const` or `static`
+const_eval_validation_mutable_ref_in_const_or_static = {$front_matter}: encountered mutable reference in a `const` or `static`
 const_eval_validation_mutable_ref_to_immutable = {$front_matter}: encountered mutable reference or box pointing to read-only memory
 const_eval_validation_never_val = {$front_matter}: encountered a value of the never type `!`
 const_eval_validation_null_box = {$front_matter}: encountered a null box

compiler/rustc_const_eval/src/errors.rs

@@ -603,18 +603,18 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
             PtrToUninhabited { ptr_kind: PointerKind::Box, .. } => {
                 const_eval_validation_box_to_uninhabited
             }
-            PtrToUninhabited { ptr_kind: PointerKind::Ref, .. } => {
+            PtrToUninhabited { ptr_kind: PointerKind::Ref(_), .. } => {
                 const_eval_validation_ref_to_uninhabited
             }
 
             PtrToStatic { ptr_kind: PointerKind::Box } => const_eval_validation_box_to_static,
-            PtrToStatic { ptr_kind: PointerKind::Ref } => const_eval_validation_ref_to_static,
+            PtrToStatic { ptr_kind: PointerKind::Ref(_) } => const_eval_validation_ref_to_static,
 
             PointerAsInt { .. } => const_eval_validation_pointer_as_int,
             PartialPointer => const_eval_validation_partial_pointer,
             ConstRefToMutable => const_eval_validation_const_ref_to_mutable,
             ConstRefToExtern => const_eval_validation_const_ref_to_extern,
-            MutableRefInConst => const_eval_validation_mutable_ref_in_const,
+            MutableRefInConstOrStatic => const_eval_validation_mutable_ref_in_const_or_static,
             MutableRefToImmutable => const_eval_validation_mutable_ref_to_immutable,
             NullFnPtr => const_eval_validation_null_fn_ptr,
             NeverVal => const_eval_validation_never_val,
@@ -630,37 +630,39 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
             InvalidMetaSliceTooLarge { ptr_kind: PointerKind::Box } => {
                 const_eval_validation_invalid_box_slice_meta
             }
-            InvalidMetaSliceTooLarge { ptr_kind: PointerKind::Ref } => {
+            InvalidMetaSliceTooLarge { ptr_kind: PointerKind::Ref(_) } => {
                 const_eval_validation_invalid_ref_slice_meta
             }
 
             InvalidMetaTooLarge { ptr_kind: PointerKind::Box } => {
                 const_eval_validation_invalid_box_meta
             }
-            InvalidMetaTooLarge { ptr_kind: PointerKind::Ref } => {
+            InvalidMetaTooLarge { ptr_kind: PointerKind::Ref(_) } => {
                 const_eval_validation_invalid_ref_meta
             }
-            UnalignedPtr { ptr_kind: PointerKind::Ref, .. } => const_eval_validation_unaligned_ref,
+            UnalignedPtr { ptr_kind: PointerKind::Ref(_), .. } => {
+                const_eval_validation_unaligned_ref
+            }
             UnalignedPtr { ptr_kind: PointerKind::Box, .. } => const_eval_validation_unaligned_box,
 
             NullPtr { ptr_kind: PointerKind::Box } => const_eval_validation_null_box,
-            NullPtr { ptr_kind: PointerKind::Ref } => const_eval_validation_null_ref,
+            NullPtr { ptr_kind: PointerKind::Ref(_) } => const_eval_validation_null_ref,
             DanglingPtrNoProvenance { ptr_kind: PointerKind::Box, .. } => {
                 const_eval_validation_dangling_box_no_provenance
             }
-            DanglingPtrNoProvenance { ptr_kind: PointerKind::Ref, .. } => {
+            DanglingPtrNoProvenance { ptr_kind: PointerKind::Ref(_), .. } => {
                 const_eval_validation_dangling_ref_no_provenance
             }
             DanglingPtrOutOfBounds { ptr_kind: PointerKind::Box } => {
                 const_eval_validation_dangling_box_out_of_bounds
             }
-            DanglingPtrOutOfBounds { ptr_kind: PointerKind::Ref } => {
+            DanglingPtrOutOfBounds { ptr_kind: PointerKind::Ref(_) } => {
                 const_eval_validation_dangling_ref_out_of_bounds
             }
             DanglingPtrUseAfterFree { ptr_kind: PointerKind::Box } => {
                 const_eval_validation_dangling_box_use_after_free
             }
-            DanglingPtrUseAfterFree { ptr_kind: PointerKind::Ref } => {
+            DanglingPtrUseAfterFree { ptr_kind: PointerKind::Ref(_) } => {
                 const_eval_validation_dangling_ref_use_after_free
             }
             InvalidBool { .. } => const_eval_validation_invalid_bool,
@@ -766,7 +768,7 @@ impl<'tcx> ReportErrorExt for ValidationErrorInfo<'tcx> {
             }
             NullPtr { .. }
             | PtrToStatic { .. }
-            | MutableRefInConst
+            | MutableRefInConstOrStatic
             | ConstRefToMutable
             | ConstRefToExtern
             | MutableRefToImmutable

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -445,22 +445,22 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
             // Determine whether this pointer expects to be pointing to something mutable.
             let ptr_expected_mutbl = match ptr_kind {
                 PointerKind::Box => Mutability::Mut,
-                PointerKind::Ref => {
-                    let tam = value.layout.ty.builtin_deref(false).unwrap();
-                    // ZST never require mutability. We do not take into account interior mutability
-                    // here since we cannot know if there really is an `UnsafeCell` inside
-                    // `Option<UnsafeCell>` -- so we check that in the recursive descent behind this
-                    // reference.
-                    if size == Size::ZERO { Mutability::Not } else { tam.mutbl }
+                PointerKind::Ref(mutbl) => {
+                    // We do not take into account interior mutability here since we cannot know if
+                    // there really is an `UnsafeCell` inside `Option<UnsafeCell>` -- so we check
+                    // that in the recursive descent behind this reference (controlled by
+                    // `allow_immutable_unsafe_cell`).
+                    mutbl
                 }
             };
             // Proceed recursively even for ZST, no reason to skip them!
             // `!` is a ZST and we want to validate it.
             if let Ok((alloc_id, _offset, _prov)) = self.ecx.ptr_try_get_alloc_id(place.ptr()) {
+                let mut skip_recursive_check = false;
                 // Let's see what kind of memory this points to.
                 // `unwrap` since dangling pointers have already been handled.
                 let alloc_kind = self.ecx.tcx.try_get_global_alloc(alloc_id).unwrap();
-                match alloc_kind {
+                let alloc_actual_mutbl = match alloc_kind {
                     GlobalAlloc::Static(did) => {
                         // Special handling for pointers to statics (irrespective of their type).
                         assert!(!self.ecx.tcx.is_thread_local_static(did));
@@ -474,12 +474,6 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                                     .no_bound_vars()
                                     .expect("statics should not have generic parameters")
                                     .is_freeze(*self.ecx.tcx, ty::ParamEnv::reveal_all());
-                        // Mutability check.
-                        if ptr_expected_mutbl == Mutability::Mut {
-                            if !is_mut {
-                                throw_validation_failure!(self.path, MutableRefToImmutable);
-                            }
-                        }
                         // Mode-specific checks
                         match self.ctfe_mode {
                             Some(
@@ -494,42 +488,49 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                                 // trigger cycle errors if we try to compute the value of the other static
                                 // and that static refers back to us (potentially through a promoted).
                                 // This could miss some UB, but that's fine.
-                                return Ok(());
+                                skip_recursive_check = true;
                             }
                             Some(CtfeValidationMode::Const { .. }) => {
-                                // For consts on the other hand we have to recursively check;
-                                // pattern matching assumes a valid value. However we better make
-                                // sure this is not mutable.
-                                if is_mut {
-                                    throw_validation_failure!(self.path, ConstRefToMutable);
-                                }
                                 // We can't recursively validate `extern static`, so we better reject them.
                                 if self.ecx.tcx.is_foreign_item(did) {
                                     throw_validation_failure!(self.path, ConstRefToExtern);
                                 }
                             }
                             None => {}
                         }
+                        // Return alloc mutability
+                        if is_mut { Mutability::Mut } else { Mutability::Not }
                     }
-                    GlobalAlloc::Memory(alloc) => {
-                        if alloc.inner().mutability == Mutability::Mut
-                            && matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. }))
-                        {
-                            throw_validation_failure!(self.path, ConstRefToMutable);
-                        }
-                        if ptr_expected_mutbl == Mutability::Mut
-                            && alloc.inner().mutability == Mutability::Not
-                        {
-                            throw_validation_failure!(self.path, MutableRefToImmutable);
-                        }
-                    }
+                    GlobalAlloc::Memory(alloc) => alloc.inner().mutability,
                     GlobalAlloc::Function(..) | GlobalAlloc::VTable(..) => {
                         // These are immutable, we better don't allow mutable pointers here.
-                        if ptr_expected_mutbl == Mutability::Mut {
-                            throw_validation_failure!(self.path, MutableRefToImmutable);
-                        }
+                        Mutability::Not
+                    }
+                };
+                // Mutability check.
+                // If this allocation has size zero, there is no actual mutability here.
+                let (size, _align, _alloc_kind) = self.ecx.get_alloc_info(alloc_id);
+                if size != Size::ZERO {
+                    if ptr_expected_mutbl == Mutability::Mut
+                        && alloc_actual_mutbl == Mutability::Not
+                    {
+                        throw_validation_failure!(self.path, MutableRefToImmutable);
+                    }
+                    if ptr_expected_mutbl == Mutability::Mut
+                        && self.ctfe_mode.is_some_and(|c| !c.may_contain_mutable_ref())
+                    {
+                        throw_validation_failure!(self.path, MutableRefInConstOrStatic);
+                    }
+                    if alloc_actual_mutbl == Mutability::Mut
+                        && matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. }))
+                    {
+                        throw_validation_failure!(self.path, ConstRefToMutable);
                     }
                 }
+                // Potentially skip recursive check.
+                if skip_recursive_check {
+                    return Ok(());
+                }
             }
             let path = &self.path;
             ref_tracking.track(place, || {
@@ -598,16 +599,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 }
                 Ok(true)
             }
-            ty::Ref(_, ty, mutbl) => {
-                if self.ctfe_mode.is_some_and(|c| !c.may_contain_mutable_ref())
-                    && *mutbl == Mutability::Mut
-                {
-                    let layout = self.ecx.layout_of(*ty)?;
-                    if !layout.is_zst() {
-                        throw_validation_failure!(self.path, MutableRefInConst);
-                    }
-                }
-                self.check_safe_pointer(value, PointerKind::Ref)?;
+            ty::Ref(_, _ty, mutbl) => {
+                self.check_safe_pointer(value, PointerKind::Ref(*mutbl))?;
                 Ok(true)
             }
             ty::FnPtr(_sig) => {

compiler/rustc_errors/src/lib.rs

@@ -526,6 +526,7 @@ pub enum StashKey {
     MaybeFruTypo,
     CallAssocMethod,
     TraitMissingMethod,
+    AssociatedTypeSuggestion,
     OpaqueHiddenTypeMismatch,
     MaybeForgetReturn,
     /// Query cycle detected, stashing in favor of a better error.

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -109,6 +109,93 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.autoderef(span, ty).any(|(ty, _)| matches!(ty.kind(), ty::Slice(..) | ty::Array(..)))
     }
 
+    fn impl_into_iterator_should_be_iterator(
+        &self,
+        ty: Ty<'tcx>,
+        span: Span,
+        unsatisfied_predicates: &Vec<(
+            ty::Predicate<'_>,
+            Option<ty::Predicate<'_>>,
+            Option<ObligationCause<'_>>,
+        )>,
+    ) -> bool {
+        fn predicate_bounds_generic_param<'tcx>(
+            predicate: ty::Predicate<'_>,
+            generics: &'tcx ty::Generics,
+            generic_param: &ty::GenericParamDef,
+            tcx: TyCtxt<'tcx>,
+        ) -> bool {
+            if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_pred)) =
+                predicate.kind().as_ref().skip_binder()
+            {
+                let ty::TraitPredicate { trait_ref: ty::TraitRef { args, .. }, .. } = trait_pred;
+                if args.is_empty() {
+                    return false;
+                }
+                let Some(arg_ty) = args[0].as_type() else {
+                    return false;
+                };
+                let ty::Param(param) = arg_ty.kind() else {
+                    return false;
+                };
+                // Is `generic_param` the same as the arg for this trait predicate?
+                generic_param.index == generics.type_param(&param, tcx).index
+            } else {
+                false
+            }
+        }
+
+        fn is_iterator_predicate(predicate: ty::Predicate<'_>, tcx: TyCtxt<'_>) -> bool {
+            if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_pred)) =
+                predicate.kind().as_ref().skip_binder()
+            {
+                tcx.is_diagnostic_item(sym::Iterator, trait_pred.trait_ref.def_id)
+            } else {
+                false
+            }
+        }
+
+        // Does the `ty` implement `IntoIterator`?
+        let Some(into_iterator_trait) = self.tcx.get_diagnostic_item(sym::IntoIterator) else {
+            return false;
+        };
+        let trait_ref = ty::TraitRef::new(self.tcx, into_iterator_trait, [ty]);
+        let cause = ObligationCause::new(span, self.body_id, ObligationCauseCode::MiscObligation);
+        let obligation = Obligation::new(self.tcx, cause, self.param_env, trait_ref);
+        if !self.predicate_must_hold_modulo_regions(&obligation) {
+            return false;
+        }
+
+        match ty.kind() {
+            ty::Param(param) => {
+                let generics = self.tcx.generics_of(self.body_id);
+                let generic_param = generics.type_param(&param, self.tcx);
+                for unsatisfied in unsatisfied_predicates.iter() {
+                    // The parameter implements `IntoIterator`
+                    // but it has called a method that requires it to implement `Iterator`
+                    if predicate_bounds_generic_param(
+                        unsatisfied.0,
+                        generics,
+                        generic_param,
+                        self.tcx,
+                    ) && is_iterator_predicate(unsatisfied.0, self.tcx)
+                    {
+                        return true;
+                    }
+                }
+            }
+            ty::Alias(ty::AliasKind::Opaque, _) => {
+                for unsatisfied in unsatisfied_predicates.iter() {
+                    if is_iterator_predicate(unsatisfied.0, self.tcx) {
+                        return true;
+                    }
+                }
+            }
+            _ => return false,
+        }
+        false
+    }
+
     #[instrument(level = "debug", skip(self))]
     pub fn report_method_error(
         &self,
@@ -555,6 +642,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     "`count` is defined on `{iterator_trait}`, which `{rcvr_ty}` does not implement"
                 ));
             }
+        } else if self.impl_into_iterator_should_be_iterator(rcvr_ty, span, unsatisfied_predicates)
+        {
+            err.span_label(span, format!("`{rcvr_ty}` is not an iterator"));
+            err.multipart_suggestion_verbose(
+                "call `.into_iter()` first",
+                vec![(span.shrink_to_lo(), format!("into_iter()."))],
+                Applicability::MaybeIncorrect,
+            );
+            return Some(err);
         } else if !unsatisfied_predicates.is_empty() && matches!(rcvr_ty.kind(), ty::Param(_)) {
             // We special case the situation where we are looking for `_` in
             // `<TypeParam as _>::method` because otherwise the machinery will look for blanket

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -12,6 +12,7 @@ use rustc_macros::HashStable;
 use rustc_session::CtfeBacktrace;
 use rustc_span::{def_id::DefId, Span, DUMMY_SP};
 use rustc_target::abi::{call, Align, Size, VariantIdx, WrappingRange};
+use rustc_type_ir::Mutability;
 
 use std::borrow::Cow;
 use std::{any::Any, backtrace::Backtrace, fmt};
@@ -367,15 +368,15 @@ pub enum UndefinedBehaviorInfo<'tcx> {
 
 #[derive(Debug, Clone, Copy)]
 pub enum PointerKind {
-    Ref,
+    Ref(Mutability),
     Box,
 }
 
 impl IntoDiagnosticArg for PointerKind {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue {
         DiagnosticArgValue::Str(
             match self {
-                Self::Ref => "ref",
+                Self::Ref(_) => "ref",
                 Self::Box => "box",
             }
             .into(),
@@ -408,7 +409,7 @@ impl From<PointerKind> for ExpectedKind {
     fn from(x: PointerKind) -> ExpectedKind {
         match x {
             PointerKind::Box => ExpectedKind::Box,
-            PointerKind::Ref => ExpectedKind::Reference,
+            PointerKind::Ref(_) => ExpectedKind::Reference,
         }
     }
 }
@@ -419,7 +420,7 @@ pub enum ValidationErrorKind<'tcx> {
     PartialPointer,
     PtrToUninhabited { ptr_kind: PointerKind, ty: Ty<'tcx> },
     PtrToStatic { ptr_kind: PointerKind },
-    MutableRefInConst,
+    MutableRefInConstOrStatic,
     ConstRefToMutable,
     ConstRefToExtern,
     MutableRefToImmutable,