Rollup of 7 pull requests

compiler/rustc_ast_lowering/src/lib.rs

@@ -57,6 +57,7 @@ use rustc_hir::def::{DefKind, LifetimeRes, Namespace, PartialRes, PerNS, Res};
 use rustc_hir::def_id::{LocalDefId, LocalDefIdMap, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::{ConstArg, GenericArg, ItemLocalMap, ParamName, TraitCandidate};
 use rustc_index::{Idx, IndexSlice, IndexVec};
+use rustc_macros::extension;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{ResolverAstLowering, TyCtxt};
 use rustc_session::parse::{add_feature_diagnostics, feature_err};
@@ -190,16 +191,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 }
 
-trait ResolverAstLoweringExt {
-    fn legacy_const_generic_args(&self, expr: &Expr) -> Option<Vec<usize>>;
-    fn get_partial_res(&self, id: NodeId) -> Option<PartialRes>;
-    fn get_import_res(&self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
-    fn get_label_res(&self, id: NodeId) -> Option<NodeId>;
-    fn get_lifetime_res(&self, id: NodeId) -> Option<LifetimeRes>;
-    fn take_extra_lifetime_params(&mut self, id: NodeId) -> Vec<(Ident, NodeId, LifetimeRes)>;
-}
-
-impl ResolverAstLoweringExt for ResolverAstLowering {
+#[extension(trait ResolverAstLoweringExt)]
+impl ResolverAstLowering {
     fn legacy_const_generic_args(&self, expr: &Expr) -> Option<Vec<usize>> {
         if let ExprKind::Path(None, path) = &expr.kind {
             // Don't perform legacy const generics rewriting if the path already

compiler/rustc_borrowck/src/facts.rs

@@ -2,6 +2,7 @@ use crate::location::{LocationIndex, LocationTable};
 use crate::BorrowIndex;
 use polonius_engine::AllFacts as PoloniusFacts;
 use polonius_engine::Atom;
+use rustc_macros::extension;
 use rustc_middle::mir::Local;
 use rustc_middle::ty::{RegionVid, TyCtxt};
 use rustc_mir_dataflow::move_paths::MovePathIndex;
@@ -24,20 +25,10 @@ impl polonius_engine::FactTypes for RustcFacts {
 
 pub type AllFacts = PoloniusFacts<RustcFacts>;
 
-pub(crate) trait AllFactsExt {
+#[extension(pub(crate) trait AllFactsExt)]
+impl AllFacts {
     /// Returns `true` if there is a need to gather `AllFacts` given the
     /// current `-Z` flags.
-    fn enabled(tcx: TyCtxt<'_>) -> bool;
-
-    fn write_to_dir(
-        &self,
-        dir: impl AsRef<Path>,
-        location_table: &LocationTable,
-    ) -> Result<(), Box<dyn Error>>;
-}
-
-impl AllFactsExt for AllFacts {
-    /// Return
     fn enabled(tcx: TyCtxt<'_>) -> bool {
         tcx.sess.opts.unstable_opts.nll_facts
             || tcx.sess.opts.unstable_opts.polonius.is_legacy_enabled()

compiler/rustc_borrowck/src/place_ext.rs

@@ -1,24 +1,16 @@
 use crate::borrow_set::LocalsStateAtExit;
 use rustc_hir as hir;
+use rustc_macros::extension;
 use rustc_middle::mir::ProjectionElem;
 use rustc_middle::mir::{Body, Mutability, Place};
 use rustc_middle::ty::{self, TyCtxt};
 
-/// Extension methods for the `Place` type.
-pub trait PlaceExt<'tcx> {
+#[extension(pub trait PlaceExt<'tcx>)]
+impl<'tcx> Place<'tcx> {
     /// Returns `true` if we can safely ignore borrows of this place.
     /// This is true whenever there is no action that the user can do
     /// to the place `self` that would invalidate the borrow. This is true
     /// for borrows of raw pointer dereferents as well as shared references.
-    fn ignore_borrow(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        body: &Body<'tcx>,
-        locals_state_at_exit: &LocalsStateAtExit,
-    ) -> bool;
-}
-
-impl<'tcx> PlaceExt<'tcx> for Place<'tcx> {
     fn ignore_borrow(
         &self,
         tcx: TyCtxt<'tcx>,

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -6,6 +6,7 @@ use rustc_hir::OpaqueTyOrigin;
 use rustc_infer::infer::InferCtxt;
 use rustc_infer::infer::TyCtxtInferExt as _;
 use rustc_infer::traits::{Obligation, ObligationCause};
+use rustc_macros::extension;
 use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable};
@@ -225,15 +226,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 }
 
-pub trait InferCtxtExt<'tcx> {
-    fn infer_opaque_definition_from_instantiation(
-        &self,
-        opaque_type_key: OpaqueTypeKey<'tcx>,
-        instantiated_ty: OpaqueHiddenType<'tcx>,
-    ) -> Ty<'tcx>;
-}
-
-impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
+#[extension(pub trait InferCtxtExt<'tcx>)]
+impl<'tcx> InferCtxt<'tcx> {
     /// Given the fully resolved, instantiated type for an opaque
     /// type, i.e., the value of an inference variable like C1 or C2
     /// (*), computes the "definition type" for an opaque type

compiler/rustc_borrowck/src/universal_regions.rs

@@ -22,6 +22,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_hir::BodyOwnerKind;
 use rustc_index::IndexVec;
 use rustc_infer::infer::NllRegionVariableOrigin;
+use rustc_macros::extension;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, InlineConstArgs, InlineConstArgsParts, RegionVid, Ty, TyCtxt};
@@ -793,27 +794,8 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
     }
 }
 
-trait InferCtxtExt<'tcx> {
-    fn replace_free_regions_with_nll_infer_vars<T>(
-        &self,
-        origin: NllRegionVariableOrigin,
-        value: T,
-    ) -> T
-    where
-        T: TypeFoldable<TyCtxt<'tcx>>;
-
-    fn replace_bound_regions_with_nll_infer_vars<T>(
-        &self,
-        origin: NllRegionVariableOrigin,
-        all_outlive_scope: LocalDefId,
-        value: ty::Binder<'tcx, T>,
-        indices: &mut UniversalRegionIndices<'tcx>,
-    ) -> T
-    where
-        T: TypeFoldable<TyCtxt<'tcx>>;
-}
-
-impl<'cx, 'tcx> InferCtxtExt<'tcx> for BorrowckInferCtxt<'cx, 'tcx> {
+#[extension(trait InferCtxtExt<'tcx>)]
+impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
     #[instrument(skip(self), level = "debug")]
     fn replace_free_regions_with_nll_infer_vars<T>(
         &self,

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -344,7 +344,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         visitor.visit_ty(ty);
     }
 
-    fn check_mut_borrow(&mut self, local: Local, kind: hir::BorrowKind) {
+    fn check_mut_borrow(&mut self, place: &Place<'_>, kind: hir::BorrowKind) {
         match self.const_kind() {
             // In a const fn all borrows are transient or point to the places given via
             // references in the arguments (so we already checked them with
@@ -355,10 +355,19 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
             // to mutable memory.
             hir::ConstContext::ConstFn => self.check_op(ops::TransientMutBorrow(kind)),
             _ => {
+                // For indirect places, we are not creating a new permanent borrow, it's just as
+                // transient as the already existing one. For reborrowing references this is handled
+                // at the top of `visit_rvalue`, but for raw pointers we handle it here.
+                // Pointers/references to `static mut` and cases where the `*` is not the first
+                // projection also end up here.
                 // Locals with StorageDead do not live beyond the evaluation and can
                 // thus safely be borrowed without being able to be leaked to the final
                 // value of the constant.
-                if self.local_has_storage_dead(local) {
+                // Note: This is only sound if every local that has a `StorageDead` has a
+                // `StorageDead` in every control flow path leading to a `return` terminator.
+                // The good news is that interning will detect if any unexpected mutable
+                // pointer slips through.
+                if place.is_indirect() || self.local_has_storage_dead(place.local) {
                     self.check_op(ops::TransientMutBorrow(kind));
                 } else {
                     self.check_op(ops::MutBorrow(kind));
@@ -390,6 +399,11 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
         trace!("visit_rvalue: rvalue={:?} location={:?}", rvalue, location);
 
         // Special-case reborrows to be more like a copy of a reference.
+        // FIXME: this does not actually handle all reborrows. It only detects cases where `*` is the outermost
+        // projection of the borrowed place, it skips deref'ing raw pointers and it skips `static`.
+        // All those cases are handled below with shared/mutable borrows.
+        // Once `const_mut_refs` is stable, we should be able to entirely remove this special case.
+        // (`const_refs_to_cell` is not needed, we already allow all borrows of indirect places anyway.)
         match *rvalue {
             Rvalue::Ref(_, kind, place) => {
                 if let Some(reborrowed_place_ref) = place_as_reborrow(self.tcx, self.body, place) {
@@ -460,7 +474,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
                 if !is_allowed {
                     self.check_mut_borrow(
-                        place.local,
+                        place,
                         if matches!(rvalue, Rvalue::Ref(..)) {
                             hir::BorrowKind::Ref
                         } else {
@@ -478,7 +492,14 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     place.as_ref(),
                 );
 
-                if borrowed_place_has_mut_interior {
+                // If the place is indirect, this is basically a reborrow. We have a reborrow
+                // special case above, but for raw pointers and pointers/references to `static` and
+                // when the `*` is not the first projection, `place_as_reborrow` does not recognize
+                // them as such, so we end up here. This should probably be considered a
+                // `TransientCellBorrow` (we consider the equivalent mutable case a
+                // `TransientMutBorrow`), but such reborrows got accidentally stabilized already and
+                // it is too much of a breaking change to take back.
+                if borrowed_place_has_mut_interior && !place.is_indirect() {
                     match self.const_kind() {
                         // In a const fn all borrows are transient or point to the places given via
                         // references in the arguments (so we already checked them with
@@ -495,6 +516,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                             // final value.
                             // Note: This is only sound if every local that has a `StorageDead` has a
                             // `StorageDead` in every control flow path leading to a `return` terminator.
+                            // The good news is that interning will detect if any unexpected mutable
+                            // pointer slips through.
                             if self.local_has_storage_dead(place.local) {
                                 self.check_op(ops::TransientCellBorrow);
                             } else {
@@ -948,6 +971,12 @@ fn place_as_reborrow<'tcx>(
 ) -> Option<PlaceRef<'tcx>> {
     match place.as_ref().last_projection() {
         Some((place_base, ProjectionElem::Deref)) => {
+            // FIXME: why do statics and raw pointers get excluded here? This makes
+            // some code involving mutable pointers unstable, but it is unclear
+            // why that code is treated differently from mutable references.
+            // Once TransientMutBorrow and TransientCellBorrow are stable,
+            // this can probably be cleaned up without any behavioral changes.
+
             // A borrow of a `static` also looks like `&(*_1)` in the MIR, but `_1` is a `const`
             // that points to the allocation for the static. Don't treat these as reborrows.
             if body.local_decls[place_base.local].is_ref_to_static() {

compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -74,6 +74,13 @@ pub trait Qualif {
         adt: AdtDef<'tcx>,
         args: GenericArgsRef<'tcx>,
     ) -> bool;
+
+    /// Returns `true` if this `Qualif` behaves sructurally for pointers and references:
+    /// the pointer/reference qualifies if and only if the pointee qualifies.
+    ///
+    /// (This is currently `false` for all our instances, but that may change in the future. Also,
+    /// by keeping it abstract, the handling of `Deref` in `in_place` becomes more clear.)
+    fn deref_structural<'tcx>(cx: &ConstCx<'_, 'tcx>) -> bool;
 }
 
 /// Constant containing interior mutability (`UnsafeCell<T>`).
@@ -103,6 +110,10 @@ impl Qualif for HasMutInterior {
         // It arises structurally for all other types.
         adt.is_unsafe_cell()
     }
+
+    fn deref_structural<'tcx>(_cx: &ConstCx<'_, 'tcx>) -> bool {
+        false
+    }
 }
 
 /// Constant containing an ADT that implements `Drop`.
@@ -131,6 +142,10 @@ impl Qualif for NeedsDrop {
     ) -> bool {
         adt.has_dtor(cx.tcx)
     }
+
+    fn deref_structural<'tcx>(_cx: &ConstCx<'_, 'tcx>) -> bool {
+        false
+    }
 }
 
 /// Constant containing an ADT that implements non-const `Drop`.
@@ -210,6 +225,10 @@ impl Qualif for NeedsNonConstDrop {
     ) -> bool {
         adt.has_non_const_dtor(cx.tcx)
     }
+
+    fn deref_structural<'tcx>(_cx: &ConstCx<'_, 'tcx>) -> bool {
+        false
+    }
 }
 
 // FIXME: Use `mir::visit::Visitor` for the `in_*` functions if/when it supports early return.
@@ -303,6 +322,11 @@ where
             return false;
         }
 
+        if matches!(elem, ProjectionElem::Deref) && !Q::deref_structural(cx) {
+            // We have to assume that this qualifies.
+            return true;
+        }
+
         place = place_base;
     }
 

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -14,6 +14,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{GenericArg, GenericParam, GenericParamKind, HirIdMap, LifetimeName, Node};
+use rustc_macros::extension;
 use rustc_middle::bug;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::resolve_bound_vars::*;
@@ -27,17 +28,8 @@ use std::fmt;
 
 use crate::errors;
 
-trait RegionExt {
-    fn early(param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg);
-
-    fn late(index: u32, param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg);
-
-    fn id(&self) -> Option<DefId>;
-
-    fn shifted(self, amount: u32) -> ResolvedArg;
-}
-
-impl RegionExt for ResolvedArg {
+#[extension(trait RegionExt)]
+impl ResolvedArg {
     fn early(param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg) {
         debug!("ResolvedArg::early: def_id={:?}", param.def_id);
         (param.def_id, ResolvedArg::EarlyBound(param.def_id.to_def_id()))

compiler/rustc_infer/src/infer/canonical/instantiate.rs

@@ -13,37 +13,23 @@ use rustc_middle::ty::{self, TyCtxt};
 
 /// FIXME(-Znext-solver): This or public because it is shared with the
 /// new trait solver implementation. We should deduplicate canonicalization.
-pub trait CanonicalExt<'tcx, V> {
+#[extension(pub trait CanonicalExt<'tcx, V>)]
+impl<'tcx, V> Canonical<'tcx, V> {
     /// Instantiate the wrapped value, replacing each canonical value
     /// with the value given in `var_values`.
     fn instantiate(&self, tcx: TyCtxt<'tcx>, var_values: &CanonicalVarValues<'tcx>) -> V
     where
-        V: TypeFoldable<TyCtxt<'tcx>>;
+        V: TypeFoldable<TyCtxt<'tcx>>,
+    {
+        self.instantiate_projected(tcx, var_values, |value| value.clone())
+    }
 
     /// Allows one to apply a instantiation to some subset of
     /// `self.value`. Invoke `projection_fn` with `self.value` to get
     /// a value V that is expressed in terms of the same canonical
     /// variables bound in `self` (usually this extracts from subset
     /// of `self`). Apply the instantiation `var_values` to this value
     /// V, replacing each of the canonical variables.
-    fn instantiate_projected<T>(
-        &self,
-        tcx: TyCtxt<'tcx>,
-        var_values: &CanonicalVarValues<'tcx>,
-        projection_fn: impl FnOnce(&V) -> T,
-    ) -> T
-    where
-        T: TypeFoldable<TyCtxt<'tcx>>;
-}
-
-impl<'tcx, V> CanonicalExt<'tcx, V> for Canonical<'tcx, V> {
-    fn instantiate(&self, tcx: TyCtxt<'tcx>, var_values: &CanonicalVarValues<'tcx>) -> V
-    where
-        V: TypeFoldable<TyCtxt<'tcx>>,
-    {
-        self.instantiate_projected(tcx, var_values, |value| value.clone())
-    }
-
     fn instantiate_projected<T>(
         &self,
         tcx: TyCtxt<'tcx>,

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

@@ -2786,19 +2786,8 @@ pub enum FailureCode {
     Error0644,
 }
 
-pub trait ObligationCauseExt<'tcx> {
-    fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
-
-    fn as_failure_code_diag(
-        &self,
-        terr: TypeError<'tcx>,
-        span: Span,
-        subdiags: Vec<TypeErrorAdditionalDiags>,
-    ) -> ObligationCauseFailureCode;
-    fn as_requirement_str(&self) -> &'static str;
-}
-
-impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
+#[extension(pub trait ObligationCauseExt<'tcx>)]
+impl<'tcx> ObligationCause<'tcx> {
     fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
         use self::FailureCode::*;
         use crate::traits::ObligationCauseCode::*;