Rollup of 14 pull requests

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -214,11 +214,7 @@ fn handle_native(name: &str) -> &str {
 }
 
 pub fn target_cpu(sess: &Session) -> &str {
-    let name = match sess.opts.cg.target_cpu {
-        Some(ref s) => &**s,
-        None => &*sess.target.cpu,
-    };
-
+    let name = sess.opts.cg.target_cpu.as_ref().unwrap_or(&sess.target.cpu);
     handle_native(name)
 }
 
@@ -254,8 +250,6 @@ pub fn handle_native_features(sess: &Session) -> Vec<String> {
 }
 
 pub fn tune_cpu(sess: &Session) -> Option<&str> {
-    match sess.opts.debugging_opts.tune_cpu {
-        Some(ref s) => Some(handle_native(&**s)),
-        None => None,
-    }
+    let name = sess.opts.debugging_opts.tune_cpu.as_ref()?;
+    Some(handle_native(name))
 }

compiler/rustc_hir/src/def.rs

@@ -5,6 +5,7 @@ use rustc_ast as ast;
 use rustc_ast::NodeId;
 use rustc_macros::HashStable_Generic;
 use rustc_span::hygiene::MacroKind;
+use rustc_span::Symbol;
 
 use std::array::IntoIter;
 use std::fmt::Debug;
@@ -34,7 +35,7 @@ pub enum CtorKind {
 #[derive(HashStable_Generic)]
 pub enum NonMacroAttrKind {
     /// Single-segment attribute defined by the language (`#[inline]`)
-    Builtin,
+    Builtin(Symbol),
     /// Multi-segment custom attribute living in a "tool module" (`#[rustfmt::skip]`).
     Tool,
     /// Single-segment custom attribute registered by a derive macro (`#[serde(default)]`).
@@ -371,7 +372,7 @@ impl CtorKind {
 impl NonMacroAttrKind {
     pub fn descr(self) -> &'static str {
         match self {
-            NonMacroAttrKind::Builtin => "built-in attribute",
+            NonMacroAttrKind::Builtin(..) => "built-in attribute",
             NonMacroAttrKind::Tool => "tool attribute",
             NonMacroAttrKind::DeriveHelper | NonMacroAttrKind::DeriveHelperCompat => {
                 "derive helper attribute"
@@ -393,7 +394,7 @@ impl NonMacroAttrKind {
             NonMacroAttrKind::Tool
             | NonMacroAttrKind::DeriveHelper
             | NonMacroAttrKind::DeriveHelperCompat => true,
-            NonMacroAttrKind::Builtin | NonMacroAttrKind::Registered => false,
+            NonMacroAttrKind::Builtin(..) | NonMacroAttrKind::Registered => false,
         }
     }
 }

compiler/rustc_infer/src/traits/util.rs

@@ -1,9 +1,10 @@
 use smallvec::smallvec;
 
 use crate::traits::{Obligation, ObligationCause, PredicateObligation};
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_middle::ty::outlives::Component;
 use rustc_middle::ty::{self, ToPredicate, TyCtxt, WithConstness};
+use rustc_span::symbol::Symbol;
 
 pub fn anonymize_predicate<'tcx>(
     tcx: TyCtxt<'tcx>,
@@ -287,6 +288,37 @@ pub fn transitive_bounds<'tcx>(
     elaborate_trait_refs(tcx, bounds).filter_to_traits()
 }
 
+/// A specialized variant of `elaborate_trait_refs` that only elaborates trait references that may
+/// define the given associated type `assoc_name`. It uses the
+/// `super_predicates_that_define_assoc_type` query to avoid enumerating super-predicates that
+/// aren't related to `assoc_item`.  This is used when resolving types like `Self::Item` or
+/// `T::Item` and helps to avoid cycle errors (see e.g. #35237).
+pub fn transitive_bounds_that_define_assoc_type<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
+    assoc_name: Symbol,
+) -> FxIndexSet<ty::PolyTraitRef<'tcx>> {
+    let mut stack: Vec<_> = bounds.collect();
+    let mut trait_refs = FxIndexSet::default();
+
+    while let Some(trait_ref) = stack.pop() {
+        if trait_refs.insert(trait_ref) {
+            let super_predicates =
+                tcx.super_predicates_that_define_assoc_type((trait_ref.def_id(), Some(assoc_name)));
+            for (super_predicate, _) in super_predicates.predicates {
+                let bound_predicate = super_predicate.bound_atom();
+                let subst_predicate = super_predicate
+                    .subst_supertrait(tcx, &bound_predicate.rebind(trait_ref.skip_binder()));
+                if let Some(binder) = subst_predicate.to_opt_poly_trait_ref() {
+                    stack.push(binder.value);
+                }
+            }
+        }
+    }
+
+    trait_refs
+}
+
 ///////////////////////////////////////////////////////////////////////////
 // Other
 ///////////////////////////////////////////////////////////////////////////

compiler/rustc_middle/src/query/mod.rs

@@ -456,12 +456,23 @@ rustc_queries! {
         /// full predicates are available (note that supertraits have
         /// additional acyclicity requirements).
         query super_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
-            desc { |tcx| "computing the supertraits of `{}`", tcx.def_path_str(key) }
+            desc { |tcx| "computing the super predicates of `{}`", tcx.def_path_str(key) }
+        }
+
+        /// The `Option<Symbol>` is the name of an associated type. If it is `None`, then this query
+        /// returns the full set of predicates. If `Some<Symbol>`, then the query returns only the
+        /// subset of super-predicates that reference traits that define the given associated type.
+        /// This is used to avoid cycles in resolving types like `T::Item`.
+        query super_predicates_that_define_assoc_type(key: (DefId, Option<rustc_span::symbol::Symbol>)) -> ty::GenericPredicates<'tcx> {
+            desc { |tcx| "computing the super traits of `{}`{}",
+                tcx.def_path_str(key.0),
+                if let Some(assoc_name) = key.1 { format!(" with associated type name `{}`", assoc_name) } else { "".to_string() },
+            }
         }
 
         /// To avoid cycles within the predicates of a single item we compute
         /// per-type-parameter predicates for resolving `T::AssocTy`.
-        query type_param_predicates(key: (DefId, LocalDefId)) -> ty::GenericPredicates<'tcx> {
+        query type_param_predicates(key: (DefId, LocalDefId, rustc_span::symbol::Symbol)) -> ty::GenericPredicates<'tcx> {
             desc { |tcx| "computing the bounds for type parameter `{}`", {
                 let id = tcx.hir().local_def_id_to_hir_id(key.1);
                 tcx.hir().ty_param_name(id)
@@ -1316,7 +1327,7 @@ rustc_queries! {
             desc { "looking up a named region" }
         }
         query is_late_bound_map(_: LocalDefId) ->
-            Option<&'tcx FxHashSet<ItemLocalId>> {
+            Option<(LocalDefId, &'tcx FxHashSet<ItemLocalId>)> {
             desc { "testing if a region is late bound" }
         }
         query object_lifetime_defaults_map(_: LocalDefId)

compiler/rustc_middle/src/ty/context.rs

@@ -3,6 +3,7 @@
 use crate::arena::Arena;
 use crate::dep_graph::DepGraph;
 use crate::hir::exports::ExportMap;
+use crate::hir::place::Place as HirPlace;
 use crate::ich::{NodeIdHashingMode, StableHashingContext};
 use crate::infer::canonical::{Canonical, CanonicalVarInfo, CanonicalVarInfos};
 use crate::lint::{struct_lint_level, LintDiagnosticBuilder, LintLevelSource};
@@ -379,7 +380,7 @@ pub struct TypeckResults<'tcx> {
 
     /// Records the reasons that we picked the kind of each closure;
     /// not all closures are present in the map.
-    closure_kind_origins: ItemLocalMap<(Span, Symbol)>,
+    closure_kind_origins: ItemLocalMap<(Span, HirPlace<'tcx>)>,
 
     /// For each fn, records the "liberated" types of its arguments
     /// and return type. Liberated means that all bound regions
@@ -642,11 +643,13 @@ impl<'tcx> TypeckResults<'tcx> {
         self.upvar_capture_map[&upvar_id]
     }
 
-    pub fn closure_kind_origins(&self) -> LocalTableInContext<'_, (Span, Symbol)> {
+    pub fn closure_kind_origins(&self) -> LocalTableInContext<'_, (Span, HirPlace<'tcx>)> {
         LocalTableInContext { hir_owner: self.hir_owner, data: &self.closure_kind_origins }
     }
 
-    pub fn closure_kind_origins_mut(&mut self) -> LocalTableInContextMut<'_, (Span, Symbol)> {
+    pub fn closure_kind_origins_mut(
+        &mut self,
+    ) -> LocalTableInContextMut<'_, (Span, HirPlace<'tcx>)> {
         LocalTableInContextMut { hir_owner: self.hir_owner, data: &mut self.closure_kind_origins }
     }
 
@@ -2056,6 +2059,43 @@ impl<'tcx> TyCtxt<'tcx> {
         self.mk_fn_ptr(sig.map_bound(|sig| ty::FnSig { unsafety: hir::Unsafety::Unsafe, ..sig }))
     }
 
+    /// Given the def_id of a Trait `trait_def_id` and the name of an associated item `assoc_name`
+    /// returns true if the `trait_def_id` defines an associated item of name `assoc_name`.
+    pub fn trait_may_define_assoc_type(self, trait_def_id: DefId, assoc_name: Symbol) -> bool {
+        self.super_traits_of(trait_def_id).any(|trait_did| {
+            self.associated_items(trait_did)
+                .find_by_name_and_kind_unhygienic(assoc_name, ty::AssocKind::Type)
+                .next()
+                .is_some()
+        })
+    }
+
+    /// Computes the def-ids of the transitive super-traits of `trait_def_id`. This (intentionally)
+    /// does not compute the full elaborated super-predicates but just the set of def-ids. It is used
+    /// to identify which traits may define a given associated type to help avoid cycle errors.
+    /// Returns a `DefId` iterator.
+    fn super_traits_of(self, trait_def_id: DefId) -> impl Iterator<Item = DefId> + 'tcx {
+        let mut set = FxHashSet::default();
+        let mut stack = vec![trait_def_id];
+
+        set.insert(trait_def_id);
+
+        iter::from_fn(move || -> Option<DefId> {
+            let trait_did = stack.pop()?;
+            let generic_predicates = self.super_predicates_of(trait_did);
+
+            for (predicate, _) in generic_predicates.predicates {
+                if let ty::PredicateAtom::Trait(data, _) = predicate.skip_binders() {
+                    if set.insert(data.def_id()) {
+                        stack.push(data.def_id());
+                    }
+                }
+            }
+
+            Some(trait_did)
+        })
+    }
+
     /// Given a closure signature, returns an equivalent fn signature. Detuples
     /// and so forth -- so e.g., if we have a sig with `Fn<(u32, i32)>` then
     /// you would get a `fn(u32, i32)`.
@@ -2578,7 +2618,8 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn is_late_bound(self, id: HirId) -> bool {
-        self.is_late_bound_map(id.owner).map_or(false, |set| set.contains(&id.local_id))
+        self.is_late_bound_map(id.owner)
+            .map_or(false, |(owner, set)| owner == id.owner && set.contains(&id.local_id))
     }
 
     pub fn object_lifetime_defaults(self, id: HirId) -> Option<&'tcx [ObjectLifetimeDefault]> {

compiler/rustc_middle/src/ty/mod.rs

@@ -17,7 +17,9 @@ pub use self::IntVarValue::*;
 pub use self::Variance::*;
 
 use crate::hir::exports::ExportMap;
-use crate::hir::place::Place as HirPlace;
+use crate::hir::place::{
+    Place as HirPlace, PlaceBase as HirPlaceBase, ProjectionKind as HirProjectionKind,
+};
 use crate::ich::StableHashingContext;
 use crate::middle::cstore::CrateStoreDyn;
 use crate::middle::resolve_lifetime::ObjectLifetimeDefault;
@@ -318,6 +320,16 @@ impl<'tcx> AssociatedItems<'tcx> {
             .find(|item| tcx.hygienic_eq(ident, item.ident, parent_def_id))
     }
 
+    /// Returns the associated item with the given name and `AssocKind`, if one exists, ignoring
+    /// hygiene.
+    pub fn find_by_name_and_kind_unhygienic(
+        &self,
+        name: Symbol,
+        kind: AssocKind,
+    ) -> impl '_ + Iterator<Item = &ty::AssocItem> {
+        self.filter_by_name_unhygienic(name).filter(move |item| item.kind == kind)
+    }
+
     /// Returns the associated item with the given name in the given `Namespace`, if one exists.
     pub fn find_by_name_and_namespace(
         &self,
@@ -734,6 +746,43 @@ pub struct CapturedPlace<'tcx> {
     pub info: CaptureInfo<'tcx>,
 }
 
+pub fn place_to_string_for_capture(tcx: TyCtxt<'tcx>, place: &HirPlace<'tcx>) -> String {
+    let name = match place.base {
+        HirPlaceBase::Upvar(upvar_id) => tcx.hir().name(upvar_id.var_path.hir_id).to_string(),
+        _ => bug!("Capture_information should only contain upvars"),
+    };
+    let mut curr_string = name;
+
+    for (i, proj) in place.projections.iter().enumerate() {
+        match proj.kind {
+            HirProjectionKind::Deref => {
+                curr_string = format!("*{}", curr_string);
+            }
+            HirProjectionKind::Field(idx, variant) => match place.ty_before_projection(i).kind() {
+                ty::Adt(def, ..) => {
+                    curr_string = format!(
+                        "{}.{}",
+                        curr_string,
+                        def.variants[variant].fields[idx as usize].ident.name.as_str()
+                    );
+                }
+                ty::Tuple(_) => {
+                    curr_string = format!("{}.{}", curr_string, idx);
+                }
+                _ => {
+                    bug!(
+                        "Field projection applied to a type other than Adt or Tuple: {:?}.",
+                        place.ty_before_projection(i).kind()
+                    )
+                }
+            },
+            proj => bug!("{:?} unexpected because it isn't captured", proj),
+        }
+    }
+
+    curr_string.to_string()
+}
+
 /// Part of `MinCaptureInformationMap`; describes the capture kind (&, &mut, move)
 /// for a particular capture as well as identifying the part of the source code
 /// that triggered this capture to occur.

compiler/rustc_middle/src/ty/query/keys.rs

@@ -149,6 +149,28 @@ impl Key for (LocalDefId, DefId) {
     }
 }
 
+impl Key for (DefId, Option<Symbol>) {
+    type CacheSelector = DefaultCacheSelector;
+
+    fn query_crate(&self) -> CrateNum {
+        self.0.krate
+    }
+    fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
+        tcx.def_span(self.0)
+    }
+}
+
+impl Key for (DefId, LocalDefId, Symbol) {
+    type CacheSelector = DefaultCacheSelector;
+
+    fn query_crate(&self) -> CrateNum {
+        self.0.krate
+    }
+    fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
+        self.1.default_span(tcx)
+    }
+}
+
 impl Key for (CrateNum, DefId) {
     type CacheSelector = DefaultCacheSelector;
 

compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs

@@ -1616,28 +1616,25 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     fn classify_drop_access_kind(&self, place: PlaceRef<'tcx>) -> StorageDeadOrDrop<'tcx> {
         let tcx = self.infcx.tcx;
-        match place.projection {
-            [] => StorageDeadOrDrop::LocalStorageDead,
-            [proj_base @ .., elem] => {
+        match place.last_projection() {
+            None => StorageDeadOrDrop::LocalStorageDead,
+            Some((place_base, elem)) => {
                 // FIXME(spastorino) make this iterate
-                let base_access = self.classify_drop_access_kind(PlaceRef {
-                    local: place.local,
-                    projection: proj_base,
-                });
+                let base_access = self.classify_drop_access_kind(place_base);
                 match elem {
                     ProjectionElem::Deref => match base_access {
                         StorageDeadOrDrop::LocalStorageDead
                         | StorageDeadOrDrop::BoxedStorageDead => {
                             assert!(
-                                Place::ty_from(place.local, proj_base, self.body, tcx).ty.is_box(),
+                                place_base.ty(self.body, tcx).ty.is_box(),
                                 "Drop of value behind a reference or raw pointer"
                             );
                             StorageDeadOrDrop::BoxedStorageDead
                         }
                         StorageDeadOrDrop::Destructor(_) => base_access,
                     },
                     ProjectionElem::Field(..) | ProjectionElem::Downcast(..) => {
-                        let base_ty = Place::ty_from(place.local, proj_base, self.body, tcx).ty;
+                        let base_ty = place_base.ty(self.body, tcx).ty;
                         match base_ty.kind() {
                             ty::Adt(def, _) if def.has_dtor(tcx) => {
                                 // Report the outermost adt with a destructor
@@ -1652,7 +1649,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             _ => base_access,
                         }
                     }
-
                     ProjectionElem::ConstantIndex { .. }
                     | ProjectionElem::Subslice { .. }
                     | ProjectionElem::Index(_) => base_access,