Auto merge of rust-lang#93795 - JohnTitor:rollup-n0dmsoo, r=JohnTitor

Rollup of 7 pull requests

Successful merges:

 - rust-lang#93445 (Add From<u8> for ExitCode)
 - rust-lang#93694 (rustdoc: tweak line spacing and paragraph spacing for accessibility)
 - rust-lang#93735 (Stabilize int_abs_diff in 1.60.0.)
 - rust-lang#93746 (Remove defaultness from ImplItem.)
 - rust-lang#93748 (rustc_query_impl: reduce visibility of some modules/fn's)
 - rust-lang#93751 (Drop tracking: track borrows of projections)
 - rust-lang#93781 (update `ty::TyKind` documentation)

Failed merges:

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

compiler/rustc_ast_lowering/src/item.rs

@@ -894,17 +894,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
             AssocItemKind::MacCall(..) => panic!("`TyMac` should have been expanded by now"),
         };
 
-        // Since `default impl` is not yet implemented, this is always true in impls.
-        let has_value = true;
-        let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
         let hir_id = self.lower_node_id(i.id);
         self.lower_attrs(hir_id, &i.attrs);
         let item = hir::ImplItem {
             def_id: hir_id.expect_owner(),
             ident: self.lower_ident(i.ident),
             generics,
             vis: self.lower_visibility(&i.vis),
-            defaultness,
             kind,
             span: self.lower_span(i.span),
         };

compiler/rustc_hir/src/hir.rs

@@ -2112,7 +2112,6 @@ pub struct ImplItem<'hir> {
     pub ident: Ident,
     pub def_id: LocalDefId,
     pub vis: Visibility<'hir>,
-    pub defaultness: Defaultness,
     pub generics: Generics<'hir>,
     pub kind: ImplItemKind<'hir>,
     pub span: Span,
@@ -3310,6 +3309,6 @@ mod size_asserts {
 
     rustc_data_structures::static_assert_size!(super::Item<'static>, 184);
     rustc_data_structures::static_assert_size!(super::TraitItem<'static>, 128);
-    rustc_data_structures::static_assert_size!(super::ImplItem<'static>, 152);
+    rustc_data_structures::static_assert_size!(super::ImplItem<'static>, 144);
     rustc_data_structures::static_assert_size!(super::ForeignItem<'static>, 136);
 }

compiler/rustc_hir/src/intravisit.rs

@@ -1020,12 +1020,10 @@ pub fn walk_trait_item_ref<'v, V: Visitor<'v>>(visitor: &mut V, trait_item_ref:
 
 pub fn walk_impl_item<'v, V: Visitor<'v>>(visitor: &mut V, impl_item: &'v ImplItem<'v>) {
     // N.B., deliberately force a compilation error if/when new fields are added.
-    let ImplItem { def_id: _, ident, ref vis, ref defaultness, ref generics, ref kind, span: _ } =
-        *impl_item;
+    let ImplItem { def_id: _, ident, ref vis, ref generics, ref kind, span: _ } = *impl_item;
 
     visitor.visit_ident(ident);
     visitor.visit_vis(vis);
-    visitor.visit_defaultness(defaultness);
     visitor.visit_generics(generics);
     match *kind {
         ImplItemKind::Const(ref ty, body) => {

compiler/rustc_hir/src/stable_hash_impls.rs

@@ -164,13 +164,11 @@ impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for TraitItem<'_> {
 
 impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for ImplItem<'_> {
     fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
-        let ImplItem { def_id: _, ident, ref vis, defaultness, ref generics, ref kind, span } =
-            *self;
+        let ImplItem { def_id: _, ident, ref vis, ref generics, ref kind, span } = *self;
 
         hcx.hash_hir_item_like(|hcx| {
             ident.name.hash_stable(hcx, hasher);
             vis.hash_stable(hcx, hasher);
-            defaultness.hash_stable(hcx, hasher);
             generics.hash_stable(hcx, hasher);
             kind.hash_stable(hcx, hasher);
             span.hash_stable(hcx, hasher);

compiler/rustc_hir_pretty/src/lib.rs

@@ -923,7 +923,6 @@ impl<'a> State<'a> {
         self.hardbreak_if_not_bol();
         self.maybe_print_comment(ii.span.lo());
         self.print_outer_attributes(self.attrs(ii.hir_id()));
-        self.print_defaultness(ii.defaultness);
 
         match ii.kind {
             hir::ImplItemKind::Const(ref ty, expr) => {

compiler/rustc_interface/src/tests.rs

@@ -730,6 +730,7 @@ fn test_debugging_options_tracking_hash() {
     tracked!(debug_info_for_profiling, true);
     tracked!(debug_macros, true);
     tracked!(dep_info_omit_d_target, true);
+    tracked!(drop_tracking, true);
     tracked!(dual_proc_macros, true);
     tracked!(fewer_names, Some(true));
     tracked!(force_unstable_if_unmarked, true);

compiler/rustc_middle/src/ty/sty.rs

@@ -74,10 +74,10 @@ impl BoundRegionKind {
     }
 }
 
-/// Defines the kinds of types.
+/// Defines the kinds of types used by the type system.
 ///
-/// N.B., if you change this, you'll probably want to change the corresponding
-/// AST structure in `rustc_ast/src/ast.rs` as well.
+/// Types written by the user start out as [hir::TyKind](rustc_hir::TyKind) and get
+/// converted to this representation using `AstConv::ast_ty_to_ty`.
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable, Debug)]
 #[derive(HashStable)]
 #[rustc_diagnostic_item = "TyKind"]
@@ -100,10 +100,11 @@ pub enum TyKind<'tcx> {
 
     /// Algebraic data types (ADT). For example: structures, enumerations and unions.
     ///
-    /// InternalSubsts here, possibly against intuition, *may* contain `Param`s.
-    /// That is, even after substitution it is possible that there are type
-    /// variables. This happens when the `Adt` corresponds to an ADT
-    /// definition and not a concrete use of it.
+    /// For example, the type `List<i32>` would be represented using the `AdtDef`
+    /// for `struct List<T>` and the substs `[i32]`.
+    ///
+    /// Note that generic parameters in fields only get lazily substituted
+    /// by using something like `adt_def.all_fields().map(|field| field.ty(tcx, substs))`.
     Adt(&'tcx AdtDef, SubstsRef<'tcx>),
 
     /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
@@ -112,7 +113,7 @@ pub enum TyKind<'tcx> {
     /// The pointee of a string slice. Written as `str`.
     Str,
 
-    /// An array with the given length. Written as `[T; n]`.
+    /// An array with the given length. Written as `[T; N]`.
     Array(Ty<'tcx>, &'tcx ty::Const<'tcx>),
 
     /// The pointee of an array slice. Written as `[T]`.
@@ -126,11 +127,12 @@ pub enum TyKind<'tcx> {
     Ref(Region<'tcx>, Ty<'tcx>, hir::Mutability),
 
     /// The anonymous type of a function declaration/definition. Each
-    /// function has a unique type, which is output (for a function
-    /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
+    /// function has a unique type.
     ///
-    /// For example the type of `bar` here:
+    /// For the function `fn foo() -> i32 { 3 }` this type would be
+    /// shown to the user as `fn() -> i32 {foo}`.
     ///
+    /// For example the type of `bar` here:
     /// ```rust
     /// fn foo() -> i32 { 1 }
     /// let bar = foo; // bar: fn() -> i32 {foo}
@@ -139,6 +141,9 @@ pub enum TyKind<'tcx> {
 
     /// A pointer to a function. Written as `fn() -> i32`.
     ///
+    /// Note that both functions and closures start out as either
+    /// [FnDef] or [Closure] which can be then be coerced to this variant.
+    ///
     /// For example the type of `bar` here:
     ///
     /// ```rust
@@ -150,17 +155,41 @@ pub enum TyKind<'tcx> {
     /// A trait object. Written as `dyn for<'b> Trait<'b, Assoc = u32> + Send + 'a`.
     Dynamic(&'tcx List<Binder<'tcx, ExistentialPredicate<'tcx>>>, ty::Region<'tcx>),
 
-    /// The anonymous type of a closure. Used to represent the type of
-    /// `|a| a`.
-    /// For the order of the substs see the `ClosureSubsts` type's documentation.
+    /// The anonymous type of a closure. Used to represent the type of `|a| a`.
+    ///
+    /// Closure substs contain both the - potentially substituted - generic parameters
+    /// of its parent and some synthetic parameters. See the documentation for
+    /// [ClosureSubsts] for more details.
     Closure(DefId, SubstsRef<'tcx>),
 
     /// The anonymous type of a generator. Used to represent the type of
     /// `|a| yield a`.
+    ///
+    /// For more info about generator substs, visit the documentation for
+    /// [GeneratorSubsts].
     Generator(DefId, SubstsRef<'tcx>, hir::Movability),
 
     /// A type representing the types stored inside a generator.
-    /// This should only appear in GeneratorInteriors.
+    /// This should only appear as part of the [GeneratorSubsts].
+    ///
+    /// Note that the captured variables for generators are stored separately
+    /// using a tuple in the same way as for closures.
+    ///
+    /// Unlike upvars, the witness can reference lifetimes from
+    /// inside of the generator itself. To deal with them in
+    /// the type of the generator, we convert them to higher ranked
+    /// lifetimes bound by the witness itself.
+    ///
+    /// Looking at the following example, the witness for this generator
+    /// may end up as something like `for<'a> [Vec<i32>, &'a Vec<i32>]`:
+    ///
+    /// ```rust
+    /// |a| {
+    ///     let x = &vec![3];
+    ///     yield a;
+    ///     yield x[0];
+    /// }
+    /// ```
     GeneratorWitness(Binder<'tcx, &'tcx List<Ty<'tcx>>>),
 
     /// The never type `!`.
@@ -175,23 +204,44 @@ pub enum TyKind<'tcx> {
     Projection(ProjectionTy<'tcx>),
 
     /// Opaque (`impl Trait`) type found in a return type.
+    ///
     /// The `DefId` comes either from
     /// * the `impl Trait` ast::Ty node,
     /// * or the `type Foo = impl Trait` declaration
-    /// The substitutions are for the generics of the function in question.
-    /// After typeck, the concrete type can be found in the `types` map.
+    ///
+    /// For RPIT the substitutions are for the generics of the function,
+    /// while for TAIT it is used for the generic parameters of the alias.
+    ///
+    /// During codegen, `tcx.type_of(def_id)` can be used to get the underlying type.
     Opaque(DefId, SubstsRef<'tcx>),
 
     /// A type parameter; for example, `T` in `fn f<T>(x: T) {}`.
     Param(ParamTy),
 
-    /// Bound type variable, used only when preparing a trait query.
+    /// Bound type variable, used to represent the `'a` in `for<'a> fn(&'a ())`.
+    ///
+    /// For canonical queries, we replace inference variables with bound variables,
+    /// so e.g. when checking whether `&'_ (): Trait<_>` holds, we canonicalize that to
+    /// `for<'a, T> &'a (): Trait<T>` and then convert the introduced bound variables
+    /// back to inference variables in a new inference context when inside of the query.
+    ///
+    /// See the `rustc-dev-guide` for more details about
+    /// [higher-ranked trait bounds][1] and [canonical queries][2].
+    ///
+    /// [1]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html
+    /// [2]: https://rustc-dev-guide.rust-lang.org/traits/canonical-queries.html
     Bound(ty::DebruijnIndex, BoundTy),
 
-    /// A placeholder type - universally quantified higher-ranked type.
+    /// A placeholder type, used during higher ranked subtyping to instantiate
+    /// bound variables.
     Placeholder(ty::PlaceholderType),
 
     /// A type variable used during type checking.
+    ///
+    /// Similar to placeholders, inference variables also live in a universe to
+    /// correctly deal with higher ranked types. Though unlike placeholders,
+    /// that universe is stored in the `InferCtxt` instead of directly
+    /// inside of the type.
     Infer(InferTy),
 
     /// A placeholder for a type which could not be computed; this is

compiler/rustc_query_impl/src/plumbing.rs

@@ -299,7 +299,7 @@ macro_rules! define_queries {
         }
 
         #[allow(nonstandard_style)]
-        pub mod queries {
+        mod queries {
             use std::marker::PhantomData;
 
             $(pub struct $name<$tcx> {
@@ -353,7 +353,7 @@ macro_rules! define_queries {
         })*
 
         #[allow(nonstandard_style)]
-        pub mod query_callbacks {
+        mod query_callbacks {
             use super::*;
             use rustc_middle::dep_graph::DepNode;
             use rustc_middle::ty::query::query_keys;
@@ -402,7 +402,7 @@ macro_rules! define_queries {
                 }
             }
 
-            $(pub fn $name()-> DepKindStruct {
+            $(pub(crate) fn $name()-> DepKindStruct {
                 let is_anon = is_anon!([$($modifiers)*]);
                 let is_eval_always = is_eval_always!([$($modifiers)*]);
 

compiler/rustc_session/src/options.rs

@@ -1173,6 +1173,8 @@ options! {
     dont_buffer_diagnostics: bool = (false, parse_bool, [UNTRACKED],
         "emit diagnostics rather than buffering (breaks NLL error downgrading, sorting) \
         (default: no)"),
+    drop_tracking: bool = (false, parse_bool, [TRACKED],
+        "enables drop tracking in generators (default: no)"),
     dual_proc_macros: bool = (false, parse_bool, [TRACKED],
         "load proc macros for both target and host, but only link to the target (default: no)"),
     dump_dep_graph: bool = (false, parse_bool, [UNTRACKED],

compiler/rustc_typeck/src/check/generator_interior.rs

@@ -22,11 +22,6 @@ use tracing::debug;
 
 mod drop_ranges;
 
-// FIXME(eholk): This flag is here to give a quick way to disable drop tracking in case we find
-// unexpected breakages while it's still new. It should be removed before too long. For example,
-// see #93161.
-const ENABLE_DROP_TRACKING: bool = false;
-
 struct InteriorVisitor<'a, 'tcx> {
     fcx: &'a FnCtxt<'a, 'tcx>,
     types: FxIndexSet<ty::GeneratorInteriorTypeCause<'tcx>>,
@@ -82,7 +77,7 @@ impl<'a, 'tcx> InteriorVisitor<'a, 'tcx> {
                                 yield_data.expr_and_pat_count, self.expr_count, source_span
                             );
 
-                            if ENABLE_DROP_TRACKING
+                            if self.fcx.sess().opts.debugging_opts.drop_tracking
                                 && self
                                     .drop_ranges
                                     .is_dropped_at(hir_id, yield_data.expr_and_pat_count)
@@ -208,7 +203,7 @@ pub fn resolve_interior<'a, 'tcx>(
     };
     intravisit::walk_body(&mut visitor, body);
 
-    // Check that we visited the same amount of expressions and the RegionResolutionVisitor
+    // Check that we visited the same amount of expressions as the RegionResolutionVisitor
     let region_expr_count = visitor.region_scope_tree.body_expr_count(body_id).unwrap();
     assert_eq!(region_expr_count, visitor.expr_count);
 

compiler/rustc_typeck/src/check/generator_interior/drop_ranges.rs

@@ -37,7 +37,7 @@ pub fn compute_drop_ranges<'a, 'tcx>(
     def_id: DefId,
     body: &'tcx Body<'tcx>,
 ) -> DropRanges {
-    if super::ENABLE_DROP_TRACKING {
+    if fcx.sess().opts.debugging_opts.drop_tracking {
         let consumed_borrowed_places = find_consumed_and_borrowed(fcx, def_id, body);
 
         let num_exprs = fcx.tcx.region_scope_tree(def_id).body_expr_count(body.id()).unwrap_or(0);
@@ -116,6 +116,18 @@ impl TrackedValue {
             TrackedValue::Variable(hir_id) | TrackedValue::Temporary(hir_id) => *hir_id,
         }
     }
+
+    fn from_place_with_projections_allowed(place_with_id: &PlaceWithHirId<'_>) -> Self {
+        match place_with_id.place.base {
+            PlaceBase::Rvalue | PlaceBase::StaticItem => {
+                TrackedValue::Temporary(place_with_id.hir_id)
+            }
+            PlaceBase::Local(hir_id)
+            | PlaceBase::Upvar(ty::UpvarId { var_path: ty::UpvarPath { hir_id }, .. }) => {
+                TrackedValue::Variable(hir_id)
+            }
+        }
+    }
 }
 
 /// Represents a reason why we might not be able to convert a HirId or Place
@@ -142,15 +154,7 @@ impl TryFrom<&PlaceWithHirId<'_>> for TrackedValue {
             return Err(TrackedValueConversionError::PlaceProjectionsNotSupported);
         }
 
-        match place_with_id.place.base {
-            PlaceBase::Rvalue | PlaceBase::StaticItem => {
-                Ok(TrackedValue::Temporary(place_with_id.hir_id))
-            }
-            PlaceBase::Local(hir_id)
-            | PlaceBase::Upvar(ty::UpvarId { var_path: ty::UpvarPath { hir_id }, .. }) => {
-                Ok(TrackedValue::Variable(hir_id))
-            }
-        }
+        Ok(TrackedValue::from_place_with_projections_allowed(place_with_id))
     }
 }
 

compiler/rustc_typeck/src/check/generator_interior/drop_ranges/record_consumed_borrow.rs

@@ -96,9 +96,9 @@ impl<'tcx> expr_use_visitor::Delegate<'tcx> for ExprUseDelegate<'tcx> {
         _diag_expr_id: HirId,
         _bk: rustc_middle::ty::BorrowKind,
     ) {
-        place_with_id
-            .try_into()
-            .map_or(false, |tracked_value| self.places.borrowed.insert(tracked_value));
+        self.places
+            .borrowed
+            .insert(TrackedValue::from_place_with_projections_allowed(place_with_id));
     }
 
     fn mutate(

library/core/src/num/int_macros.rs

@@ -2420,14 +2420,14 @@ macro_rules! int_impl {
         /// Basic usage:
         ///
         /// ```
-        /// #![feature(int_abs_diff)]
         #[doc = concat!("assert_eq!(100", stringify!($SelfT), ".abs_diff(80), 20", stringify!($UnsignedT), ");")]
         #[doc = concat!("assert_eq!(100", stringify!($SelfT), ".abs_diff(110), 10", stringify!($UnsignedT), ");")]
         #[doc = concat!("assert_eq!((-100", stringify!($SelfT), ").abs_diff(80), 180", stringify!($UnsignedT), ");")]
         #[doc = concat!("assert_eq!((-100", stringify!($SelfT), ").abs_diff(-120), 20", stringify!($UnsignedT), ");")]
         #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MIN.abs_diff(", stringify!($SelfT), "::MAX), ", stringify!($UnsignedT), "::MAX);")]
         /// ```
-        #[unstable(feature = "int_abs_diff", issue = "89492")]
+        #[stable(feature = "int_abs_diff", since = "1.60.0")]
+        #[rustc_const_stable(feature = "int_abs_diff", since = "1.60.0")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]

library/core/src/num/uint_macros.rs

@@ -1635,11 +1635,11 @@ macro_rules! uint_impl {
         /// Basic usage:
         ///
         /// ```
-        /// #![feature(int_abs_diff)]
         #[doc = concat!("assert_eq!(100", stringify!($SelfT), ".abs_diff(80), 20", stringify!($SelfT), ");")]
         #[doc = concat!("assert_eq!(100", stringify!($SelfT), ".abs_diff(110), 10", stringify!($SelfT), ");")]
         /// ```
-        #[unstable(feature = "int_abs_diff", issue = "89492")]
+        #[stable(feature = "int_abs_diff", since = "1.60.0")]
+        #[rustc_const_stable(feature = "int_abs_diff", since = "1.60.0")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline]