Auto merge of rust-lang#95552 - matthiaskrgr:rollup-bxminn9, r=matthi…

…askrgr

Rollup of 6 pull requests

Successful merges:

 - rust-lang#95032 (Clean up, categorize and sort unstable features in std.)
 - rust-lang#95260 (Better suggestions for `Fn`-family trait selection errors)
 - rust-lang#95293 (suggest wrapping single-expr blocks in square brackets)
 - rust-lang#95344 (Make `impl Debug for rustdoc::clean::Item` easier to read)
 - rust-lang#95388 (interpret: make isize::MAX the limit for dynamic value sizes)
 - rust-lang#95530 (rustdoc: do not show primitives and keywords as private)

Failed merges:

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

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -23,8 +23,8 @@ use rustc_target::abi::{call::FnAbi, Align, HasDataLayout, Size, TargetDataLayou
 
 use super::{
     AllocCheck, AllocId, GlobalId, Immediate, InterpErrorInfo, InterpResult, MPlaceTy, Machine,
-    MemPlace, MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, Pointer, Provenance,
-    Scalar, ScalarMaybeUninit, StackPopJump,
+    MemPlace, MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, Pointer,
+    PointerArithmetic, Provenance, Scalar, ScalarMaybeUninit, StackPopJump,
 };
 use crate::transform::validate::equal_up_to_regions;
 
@@ -678,7 +678,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let size = size.align_to(align);
 
                 // Check if this brought us over the size limit.
-                if size.bytes() >= self.tcx.data_layout.obj_size_bound() {
+                if size > self.max_size_of_val() {
                     throw_ub!(InvalidMeta("total size is bigger than largest supported object"));
                 }
                 Ok(Some((size, align)))
@@ -694,9 +694,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let elem = layout.field(self, 0);
 
                 // Make sure the slice is not too big.
-                let size = elem.size.checked_mul(len, self).ok_or_else(|| {
-                    err_ub!(InvalidMeta("slice is bigger than largest supported object"))
-                })?;
+                let size = elem.size.bytes().saturating_mul(len); // we rely on `max_size_of_val` being smaller than `u64::MAX`.
+                let size = Size::from_bytes(size);
+                if size > self.max_size_of_val() {
+                    throw_ub!(InvalidMeta("slice is bigger than largest supported object"));
+                }
                 Ok(Some((size, elem.align.abi)))
             }
 

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -531,7 +531,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     ) -> InterpResult<'tcx, Pointer<Option<M::PointerTag>>> {
         // We cannot overflow i64 as a type's size must be <= isize::MAX.
         let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap();
-        // The computed offset, in bytes, cannot overflow an isize.
+        // The computed offset, in bytes, must not overflow an isize.
+        // `checked_mul` enforces a too small bound, but no actual allocation can be big enough for
+        // the difference to be noticeable.
         let offset_bytes =
             offset_count.checked_mul(pointee_size).ok_or(err_ub!(PointerArithOverflow))?;
         // The offset being in bounds cannot rely on "wrapping around" the address space.
@@ -563,6 +565,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let count = self.read_scalar(&count)?.to_machine_usize(self)?;
         let layout = self.layout_of(src.layout.ty.builtin_deref(true).unwrap().ty)?;
         let (size, align) = (layout.size, layout.align.abi);
+        // `checked_mul` enforces a too small bound (the correct one would probably be machine_isize_max),
+        // but no actual allocation can be big enough for the difference to be noticeable.
         let size = size.checked_mul(count, self).ok_or_else(|| {
             err_ub_format!(
                 "overflow computing total size of `{}`",
@@ -588,6 +592,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let byte = self.read_scalar(&byte)?.to_u8()?;
         let count = self.read_scalar(&count)?.to_machine_usize(self)?;
 
+        // `checked_mul` enforces a too small bound (the correct one would probably be machine_isize_max),
+        // but no actual allocation can be big enough for the difference to be noticeable.
         let len = layout
             .size
             .checked_mul(count, self)

compiler/rustc_const_eval/src/interpret/traits.rs

@@ -110,16 +110,17 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             .read_ptr_sized(pointer_size * u64::try_from(COMMON_VTABLE_ENTRIES_SIZE).unwrap())?
             .check_init()?;
         let size = size.to_machine_usize(self)?;
+        let size = Size::from_bytes(size);
         let align = vtable
             .read_ptr_sized(pointer_size * u64::try_from(COMMON_VTABLE_ENTRIES_ALIGN).unwrap())?
             .check_init()?;
         let align = align.to_machine_usize(self)?;
         let align = Align::from_bytes(align).map_err(|e| err_ub!(InvalidVtableAlignment(e)))?;
 
-        if size >= self.tcx.data_layout.obj_size_bound() {
+        if size > self.max_size_of_val() {
             throw_ub!(InvalidVtableSize);
         }
-        Ok((Size::from_bytes(size), align))
+        Ok((size, align))
     }
 
     pub fn read_new_vtable_after_trait_upcasting_from_vtable(

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1091,7 +1091,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
     /// Compares two given types, eliding parts that are the same between them and highlighting
     /// relevant differences, and return two representation of those types for highlighted printing.
-    fn cmp(&self, t1: Ty<'tcx>, t2: Ty<'tcx>) -> (DiagnosticStyledString, DiagnosticStyledString) {
+    pub fn cmp(
+        &self,
+        t1: Ty<'tcx>,
+        t2: Ty<'tcx>,
+    ) -> (DiagnosticStyledString, DiagnosticStyledString) {
         debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind());
 
         // helper functions

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

@@ -18,6 +18,11 @@ pub trait PointerArithmetic: HasDataLayout {
         self.data_layout().pointer_size
     }
 
+    #[inline(always)]
+    fn max_size_of_val(&self) -> Size {
+        Size::from_bytes(self.machine_isize_max())
+    }
+
     #[inline]
     fn machine_usize_max(&self) -> u64 {
         self.pointer_size().unsigned_int_max().try_into().unwrap()

compiler/rustc_middle/src/ty/closure.rs

@@ -119,9 +119,21 @@ impl<'tcx> ClosureKind {
     /// See `Ty::to_opt_closure_kind` for more details.
     pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
         match self {
-            ty::ClosureKind::Fn => tcx.types.i8,
-            ty::ClosureKind::FnMut => tcx.types.i16,
-            ty::ClosureKind::FnOnce => tcx.types.i32,
+            ClosureKind::Fn => tcx.types.i8,
+            ClosureKind::FnMut => tcx.types.i16,
+            ClosureKind::FnOnce => tcx.types.i32,
+        }
+    }
+
+    pub fn from_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ClosureKind> {
+        if Some(def_id) == tcx.lang_items().fn_once_trait() {
+            Some(ClosureKind::FnOnce)
+        } else if Some(def_id) == tcx.lang_items().fn_mut_trait() {
+            Some(ClosureKind::FnMut)
+        } else if Some(def_id) == tcx.lang_items().fn_trait() {
+            Some(ClosureKind::Fn)
+        } else {
+            None
         }
     }
 }

compiler/rustc_parse/src/parser/expr.rs

@@ -1919,17 +1919,13 @@ impl<'a> Parser<'a> {
         match snapshot.parse_array_or_repeat_expr(attrs, token::Brace) {
             Ok(arr) => {
                 let hi = snapshot.prev_token.span;
-                self.struct_span_err(
-                    arr.span,
-                    "this code is interpreted as a block expression, not an array",
-                )
-                .multipart_suggestion(
-                    "try using [] instead of {}",
-                    vec![(lo, "[".to_owned()), (hi, "]".to_owned())],
-                    Applicability::MaybeIncorrect,
-                )
-                .note("to define an array, one would use square brackets instead of curly braces")
-                .emit();
+                self.struct_span_err(arr.span, "this is a block expression, not an array")
+                    .multipart_suggestion(
+                        "to make an array, use square brackets instead of curly braces",
+                        vec![(lo, "[".to_owned()), (hi, "]".to_owned())],
+                        Applicability::MaybeIncorrect,
+                    )
+                    .emit();
 
                 self.restore_snapshot(snapshot);
                 Some(self.mk_expr_err(arr.span))

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -2,10 +2,10 @@ pub mod on_unimplemented;
 pub mod suggestions;
 
 use super::{
-    EvaluationResult, FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes,
-    Obligation, ObligationCause, ObligationCauseCode, OnUnimplementedDirective,
-    OnUnimplementedNote, OutputTypeParameterMismatch, Overflow, PredicateObligation,
-    SelectionContext, SelectionError, TraitNotObjectSafe,
+    EvaluationResult, FulfillmentContext, FulfillmentError, FulfillmentErrorCode,
+    MismatchedProjectionTypes, Obligation, ObligationCause, ObligationCauseCode,
+    OnUnimplementedDirective, OnUnimplementedNote, OutputTypeParameterMismatch, Overflow,
+    PredicateObligation, SelectionContext, SelectionError, TraitNotObjectSafe,
 };
 
 use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
@@ -21,6 +21,8 @@ use rustc_hir::intravisit::Visitor;
 use rustc_hir::GenericParam;
 use rustc_hir::Item;
 use rustc_hir::Node;
+use rustc_infer::infer::error_reporting::same_type_modulo_infer;
+use rustc_infer::traits::TraitEngine;
 use rustc_middle::thir::abstract_const::NotConstEvaluatable;
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::ty::error::ExpectedFound;
@@ -103,6 +105,17 @@ pub trait InferCtxtExt<'tcx> {
         found_args: Vec<ArgKind>,
         is_closure: bool,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
+
+    /// Checks if the type implements one of `Fn`, `FnMut`, or `FnOnce`
+    /// in that order, and returns the generic type corresponding to the
+    /// argument of that trait (corresponding to the closure arguments).
+    fn type_implements_fn_trait(
+        &self,
+        param_env: ty::ParamEnv<'tcx>,
+        ty: ty::Binder<'tcx, Ty<'tcx>>,
+        constness: ty::BoundConstness,
+        polarity: ty::ImplPolarity,
+    ) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()>;
 }
 
 impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
@@ -563,7 +576,64 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                         }
 
                         // Try to report a help message
-                        if !trait_ref.has_infer_types_or_consts()
+                        if is_fn_trait
+                            && let Ok((implemented_kind, params)) = self.type_implements_fn_trait(
+                                obligation.param_env,
+                                trait_ref.self_ty(),
+                                trait_predicate.skip_binder().constness,
+                                trait_predicate.skip_binder().polarity,
+                            )
+                        {
+                            // If the type implements `Fn`, `FnMut`, or `FnOnce`, suppress the following
+                            // suggestion to add trait bounds for the type, since we only typically implement
+                            // these traits once.
+
+                            // Note if the `FnMut` or `FnOnce` is less general than the trait we're trying
+                            // to implement.
+                            let selected_kind =
+                                ty::ClosureKind::from_def_id(self.tcx, trait_ref.def_id())
+                                    .expect("expected to map DefId to ClosureKind");
+                            if !implemented_kind.extends(selected_kind) {
+                                err.note(
+                                    &format!(
+                                        "`{}` implements `{}`, but it must implement `{}`, which is more general",
+                                        trait_ref.skip_binder().self_ty(),
+                                        implemented_kind,
+                                        selected_kind
+                                    )
+                                );
+                            }
+
+                            // Note any argument mismatches
+                            let given_ty = params.skip_binder();
+                            let expected_ty = trait_ref.skip_binder().substs.type_at(1);
+                            if let ty::Tuple(given) = given_ty.kind()
+                                && let ty::Tuple(expected) = expected_ty.kind()
+                            {
+                                if expected.len() != given.len() {
+                                    // Note number of types that were expected and given
+                                    err.note(
+                                        &format!(
+                                            "expected a closure taking {} argument{}, but one taking {} argument{} was given",
+                                            given.len(),
+                                            if given.len() == 1 { "" } else { "s" },
+                                            expected.len(),
+                                            if expected.len() == 1 { "" } else { "s" },
+                                        )
+                                    );
+                                } else if !same_type_modulo_infer(given_ty, expected_ty) {
+                                    // Print type mismatch
+                                    let (expected_args, given_args) =
+                                        self.cmp(given_ty, expected_ty);
+                                    err.note_expected_found(
+                                        &"a closure with arguments",
+                                        expected_args,
+                                        &"a closure with arguments",
+                                        given_args,
+                                    );
+                                }
+                            }
+                        } else if !trait_ref.has_infer_types_or_consts()
                             && self.predicate_can_apply(obligation.param_env, trait_ref)
                         {
                             // If a where-clause may be useful, remind the
@@ -1148,6 +1218,52 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
         err
     }
+
+    fn type_implements_fn_trait(
+        &self,
+        param_env: ty::ParamEnv<'tcx>,
+        ty: ty::Binder<'tcx, Ty<'tcx>>,
+        constness: ty::BoundConstness,
+        polarity: ty::ImplPolarity,
+    ) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()> {
+        self.commit_if_ok(|_| {
+            for trait_def_id in [
+                self.tcx.lang_items().fn_trait(),
+                self.tcx.lang_items().fn_mut_trait(),
+                self.tcx.lang_items().fn_once_trait(),
+            ] {
+                let Some(trait_def_id) = trait_def_id else { continue };
+                // Make a fresh inference variable so we can determine what the substitutions
+                // of the trait are.
+                let var = self.next_ty_var(TypeVariableOrigin {
+                    span: DUMMY_SP,
+                    kind: TypeVariableOriginKind::MiscVariable,
+                });
+                let substs = self.tcx.mk_substs_trait(ty.skip_binder(), &[var.into()]);
+                let obligation = Obligation::new(
+                    ObligationCause::dummy(),
+                    param_env,
+                    ty.rebind(ty::TraitPredicate {
+                        trait_ref: ty::TraitRef::new(trait_def_id, substs),
+                        constness,
+                        polarity,
+                    })
+                    .to_predicate(self.tcx),
+                );
+                let mut fulfill_cx = FulfillmentContext::new_in_snapshot();
+                fulfill_cx.register_predicate_obligation(self, obligation);
+                if fulfill_cx.select_all_or_error(self).is_empty() {
+                    return Ok((
+                        ty::ClosureKind::from_def_id(self.tcx, trait_def_id)
+                            .expect("expected to map DefId to ClosureKind"),
+                        ty.rebind(self.resolve_vars_if_possible(var)),
+                    ));
+                }
+            }
+
+            Err(())
+        })
+    }
 }
 
 trait InferCtxtPrivExt<'hir, 'tcx> {

compiler/rustc_typeck/src/check/demand.rs

@@ -39,6 +39,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.suggest_no_capture_closure(err, expected, expr_ty);
         self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty);
         self.suggest_missing_parentheses(err, expr);
+        self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected);
         self.note_need_for_fn_pointer(err, expected, expr_ty);
         self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
         self.report_closure_inferred_return_type(err, expected);