Rollup of 9 pull requests

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -1,3 +1,4 @@
+use std::cell::OnceCell;
 use std::collections::VecDeque;
 use std::rc::Rc;
 
@@ -197,8 +198,8 @@ pub struct RegionInferenceContext<'tcx> {
 
     /// Reverse of the SCC constraint graph --  i.e., an edge `A -> B` exists if
     /// `B: A`. This is used to compute the universal regions that are required
-    /// to outlive a given SCC. Computed lazily.
-    rev_scc_graph: Option<ReverseSccGraph>,
+    /// to outlive a given SCC.
+    rev_scc_graph: OnceCell<ReverseSccGraph>,
 
     /// The "R0 member of [R1..Rn]" constraints, indexed by SCC.
     member_constraints: Rc<MemberConstraintSet<'tcx, ConstraintSccIndex>>,
@@ -502,7 +503,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             constraint_graph,
             constraint_sccs,
             scc_annotations,
-            rev_scc_graph: None,
+            rev_scc_graph: OnceCell::new(),
             member_constraints,
             member_constraints_applied: Vec::new(),
             universe_causes,
@@ -809,9 +810,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         member_constraint_index: NllMemberConstraintIndex,
         choice_regions: &[ty::RegionVid],
     ) {
-        // Lazily compute the reverse graph, we'll need it later.
-        self.compute_reverse_scc_graph();
-
         // Create a mutable vector of the options. We'll try to winnow
         // them down.
         let mut choice_regions: Vec<ty::RegionVid> = choice_regions.to_vec();
@@ -849,7 +847,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         // R0`). Therefore, we need only keep an option `O` if `UB: O`
         // for all UB.
         let universal_region_relations = &self.universal_region_relations;
-        for ub in self.rev_scc_graph.as_ref().unwrap().upper_bounds(scc) {
+        for ub in self.reverse_scc_graph().upper_bounds(scc) {
             debug!(?ub);
             choice_regions.retain(|&o_r| universal_region_relations.outlives(ub, o_r));
         }

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -215,9 +215,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 // FIXME: We could probably compute the LUB if there is one.
                 let scc = self.constraint_sccs.scc(vid);
                 let upper_bounds: Vec<_> = self
-                    .rev_scc_graph
-                    .as_ref()
-                    .unwrap()
+                    .reverse_scc_graph()
                     .upper_bounds(scc)
                     .filter_map(|vid| self.definitions[vid].external_name)
                     .filter(|r| !r.is_static())

compiler/rustc_borrowck/src/region_infer/reverse_sccs.rs

@@ -59,13 +59,10 @@ impl ReverseSccGraph {
 }
 
 impl RegionInferenceContext<'_> {
-    /// Compute the reverse SCC-based constraint graph (lazily).
-    pub(super) fn compute_reverse_scc_graph(&mut self) {
-        if self.rev_scc_graph.is_some() {
-            return;
-        }
-
-        self.rev_scc_graph =
-            Some(ReverseSccGraph::compute(&self.constraint_sccs, self.universal_regions()));
+    /// Return the reverse graph of the region SCCs, initialising it if needed.
+    pub(super) fn reverse_scc_graph(&self) -> &ReverseSccGraph {
+        self.rev_scc_graph.get_or_init(|| {
+            ReverseSccGraph::compute(&self.constraint_sccs, self.universal_regions())
+        })
     }
 }

compiler/rustc_mir_transform/src/elaborate_drop.rs

@@ -1,6 +1,7 @@
 use std::{fmt, iter, mem};
 
 use rustc_abi::{FIRST_VARIANT, FieldIdx, VariantIdx};
+use rustc_hir::def::DefKind;
 use rustc_hir::lang_items::LangItem;
 use rustc_index::Idx;
 use rustc_middle::mir::*;
@@ -254,8 +255,19 @@ where
             // impl_item_refs may be empty if drop fn is not implemented in 'impl AsyncDrop for ...'
             // (#140974).
             // Such code will report error, so just generate sync drop here and return
-            let Some(drop_fn_def_id) =
-                tcx.associated_item_def_ids(drop_trait).into_iter().nth(0).copied()
+            let Some(drop_fn_def_id) = tcx
+                .associated_item_def_ids(drop_trait)
+                .first()
+                .and_then(|def_id| {
+                    if tcx.def_kind(def_id) == DefKind::AssocFn
+                        && tcx.check_args_compatible(*def_id, trait_args)
+                    {
+                        Some(def_id)
+                    } else {
+                        None
+                    }
+                })
+                .copied()
             else {
                 tcx.dcx().span_delayed_bug(
                     self.elaborator.body().span,

compiler/rustc_resolve/src/late.rs

@@ -415,7 +415,7 @@ pub(crate) enum AliasPossibility {
 }
 
 #[derive(Copy, Clone, Debug)]
-pub(crate) enum PathSource<'a> {
+pub(crate) enum PathSource<'a, 'c> {
     /// Type paths `Path`.
     Type,
     /// Trait paths in bounds or impls.
@@ -429,7 +429,10 @@ pub(crate) enum PathSource<'a> {
     /// Paths in tuple struct patterns `Path(..)`.
     TupleStruct(Span, &'a [Span]),
     /// `m::A::B` in `<T as m::A>::B::C`.
-    TraitItem(Namespace),
+    ///
+    /// Second field holds the "cause" of this one, i.e. the context within
+    /// which the trait item is resolved. Used for diagnostics.
+    TraitItem(Namespace, &'c PathSource<'a, 'c>),
     /// Paths in delegation item
     Delegation,
     /// An arg in a `use<'a, N>` precise-capturing bound.
@@ -440,7 +443,7 @@ pub(crate) enum PathSource<'a> {
     DefineOpaques,
 }
 
-impl<'a> PathSource<'a> {
+impl<'a> PathSource<'a, '_> {
     fn namespace(self) -> Namespace {
         match self {
             PathSource::Type
@@ -452,7 +455,7 @@ impl<'a> PathSource<'a> {
             | PathSource::TupleStruct(..)
             | PathSource::Delegation
             | PathSource::ReturnTypeNotation => ValueNS,
-            PathSource::TraitItem(ns) => ns,
+            PathSource::TraitItem(ns, _) => ns,
             PathSource::PreciseCapturingArg(ns) => ns,
         }
     }
@@ -480,8 +483,9 @@ impl<'a> PathSource<'a> {
             PathSource::Trait(_) => "trait",
             PathSource::Pat => "unit struct, unit variant or constant",
             PathSource::Struct => "struct, variant or union type",
-            PathSource::TupleStruct(..) => "tuple struct or tuple variant",
-            PathSource::TraitItem(ns) => match ns {
+            PathSource::TraitItem(ValueNS, PathSource::TupleStruct(..))
+            | PathSource::TupleStruct(..) => "tuple struct or tuple variant",
+            PathSource::TraitItem(ns, _) => match ns {
                 TypeNS => "associated type",
                 ValueNS => "method or associated constant",
                 MacroNS => bug!("associated macro"),
@@ -585,7 +589,7 @@ impl<'a> PathSource<'a> {
                 ) | Res::SelfTyParam { .. }
                     | Res::SelfTyAlias { .. }
             ),
-            PathSource::TraitItem(ns) => match res {
+            PathSource::TraitItem(ns, _) => match res {
                 Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) if ns == ValueNS => true,
                 Res::Def(DefKind::AssocTy, _) if ns == TypeNS => true,
                 _ => false,
@@ -2007,7 +2011,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         &mut self,
         partial_res: PartialRes,
         path: &[Segment],
-        source: PathSource<'_>,
+        source: PathSource<'_, '_>,
         path_span: Span,
     ) {
         let proj_start = path.len() - partial_res.unresolved_segments();
@@ -4206,7 +4210,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         id: NodeId,
         qself: &Option<P<QSelf>>,
         path: &Path,
-        source: PathSource<'ast>,
+        source: PathSource<'ast, '_>,
     ) {
         self.smart_resolve_path_fragment(
             qself,
@@ -4223,7 +4227,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         &mut self,
         qself: &Option<P<QSelf>>,
         path: &[Segment],
-        source: PathSource<'ast>,
+        source: PathSource<'ast, '_>,
         finalize: Finalize,
         record_partial_res: RecordPartialRes,
         parent_qself: Option<&QSelf>,
@@ -4404,6 +4408,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             path_span,
             source.defer_to_typeck(),
             finalize,
+            source,
         ) {
             Ok(Some(partial_res)) if let Some(res) = partial_res.full_res() => {
                 // if we also have an associated type that matches the ident, stash a suggestion
@@ -4526,12 +4531,13 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         span: Span,
         defer_to_typeck: bool,
         finalize: Finalize,
+        source: PathSource<'ast, '_>,
     ) -> Result<Option<PartialRes>, Spanned<ResolutionError<'ra>>> {
         let mut fin_res = None;
 
         for (i, &ns) in [primary_ns, TypeNS, ValueNS].iter().enumerate() {
             if i == 0 || ns != primary_ns {
-                match self.resolve_qpath(qself, path, ns, finalize)? {
+                match self.resolve_qpath(qself, path, ns, finalize, source)? {
                     Some(partial_res)
                         if partial_res.unresolved_segments() == 0 || defer_to_typeck =>
                     {
@@ -4568,6 +4574,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         path: &[Segment],
         ns: Namespace,
         finalize: Finalize,
+        source: PathSource<'ast, '_>,
     ) -> Result<Option<PartialRes>, Spanned<ResolutionError<'ra>>> {
         debug!(
             "resolve_qpath(qself={:?}, path={:?}, ns={:?}, finalize={:?})",
@@ -4615,7 +4622,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             let partial_res = self.smart_resolve_path_fragment(
                 &None,
                 &path[..=qself.position],
-                PathSource::TraitItem(ns),
+                PathSource::TraitItem(ns, &source),
                 Finalize::with_root_span(finalize.node_id, finalize.path_span, qself.path_span),
                 RecordPartialRes::No,
                 Some(&qself),