Auto merge of #42276 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 6 pull requests

- Successful merges: #42207, #42217, #42249, #42251, #42260, #42266
- Failed merges:

src/libcollections/binary_heap.rs

@@ -43,8 +43,11 @@
 //! // instead of a max-heap.
 //! impl Ord for State {
 //!     fn cmp(&self, other: &State) -> Ordering {
-//!         // Notice that the we flip the ordering here
+//!         // Notice that the we flip the ordering on costs.
+//!         // In case of a tie we compare positions - this step is necessary
+//!         // to make implementations of `PartialEq` and `Ord` consistent.
 //!         other.cost.cmp(&self.cost)
+//!             .then_with(|| self.position.cmp(&other.position))
 //!     }
 //! }
 //!

src/libcore/cmp.rs

@@ -67,6 +67,10 @@ use self::Ordering::*;
 /// the rule that `eq` is a strict inverse of `ne`; that is, `!(a == b)` if and
 /// only if `a != b`.
 ///
+/// Implementations of `PartialEq`, `PartialOrd`, and `Ord` *must* agree with
+/// each other. It's easy to accidentally make them disagree by deriving some
+/// of the traits and manually implementing others.
+///
 /// An example implementation for a domain in which two books are considered
 /// the same book if their ISBN matches, even if the formats differ:
 ///
@@ -386,6 +390,10 @@ impl<T: Ord> Ord for Reverse<T> {
 /// Then you must define an implementation for `cmp()`. You may find it useful to use
 /// `cmp()` on your type's fields.
 ///
+/// Implementations of `PartialEq`, `PartialOrd`, and `Ord` *must* agree with each other. It's
+/// easy to accidentally make them disagree by deriving some of the traits and manually
+/// implementing others.
+///
 /// Here's an example where you want to sort people by height only, disregarding `id`
 /// and `name`:
 ///
@@ -474,15 +482,19 @@ impl PartialOrd for Ordering {
 ///
 /// ## How can I implement `PartialOrd`?
 ///
-/// PartialOrd only requires implementation of the `partial_cmp` method, with the others generated
-/// from default implementations.
+/// `PartialOrd` only requires implementation of the `partial_cmp` method, with the others
+/// generated from default implementations.
 ///
 /// However it remains possible to implement the others separately for types which do not have a
 /// total order. For example, for floating point numbers, `NaN < 0 == false` and `NaN >= 0 ==
 /// false` (cf. IEEE 754-2008 section 5.11).
 ///
 /// `PartialOrd` requires your type to be `PartialEq`.
 ///
+/// Implementations of `PartialEq`, `PartialOrd`, and `Ord` *must* agree with each other. It's
+/// easy to accidentally make them disagree by deriving some of the traits and manually
+/// implementing others.
+///
 /// If your type is `Ord`, you can implement `partial_cmp()` by using `cmp()`:
 ///
 /// ```

src/librustc/ty/context.rs

@@ -40,7 +40,7 @@ use ty::layout::{Layout, TargetDataLayout};
 use ty::inhabitedness::DefIdForest;
 use ty::maps;
 use ty::steal::Steal;
-use util::nodemap::{NodeMap, NodeSet, DefIdMap, DefIdSet};
+use util::nodemap::{NodeMap, NodeSet, DefIdSet};
 use util::nodemap::{FxHashMap, FxHashSet};
 use rustc_data_structures::accumulate_vec::AccumulateVec;
 
@@ -499,33 +499,6 @@ pub struct GlobalCtxt<'tcx> {
     /// Maps Expr NodeId's to `true` iff `&expr` can have 'static lifetime.
     pub rvalue_promotable_to_static: RefCell<NodeMap<bool>>,
 
-    /// Maps Fn items to a collection of fragment infos.
-    ///
-    /// The main goal is to identify data (each of which may be moved
-    /// or assigned) whose subparts are not moved nor assigned
-    /// (i.e. their state is *unfragmented*) and corresponding ast
-    /// nodes where the path to that data is moved or assigned.
-    ///
-    /// In the long term, unfragmented values will have their
-    /// destructor entirely driven by a single stack-local drop-flag,
-    /// and their parents, the collections of the unfragmented values
-    /// (or more simply, "fragmented values"), are mapped to the
-    /// corresponding collections of stack-local drop-flags.
-    ///
-    /// (However, in the short term that is not the case; e.g. some
-    /// unfragmented paths still need to be zeroed, namely when they
-    /// reference parent data from an outer scope that was not
-    /// entirely moved, and therefore that needs to be zeroed so that
-    /// we do not get double-drop when we hit the end of the parent
-    /// scope.)
-    ///
-    /// Also: currently the table solely holds keys for node-ids of
-    /// unfragmented values (see `FragmentInfo` enum definition), but
-    /// longer-term we will need to also store mappings from
-    /// fragmented data to the set of unfragmented pieces that
-    /// constitute it.
-    pub fragment_infos: RefCell<DefIdMap<Vec<ty::FragmentInfo>>>,
-
     /// The definite name of the current crate after taking into account
     /// attributes, commandline parameters, etc.
     pub crate_name: Symbol,
@@ -730,7 +703,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             selection_cache: traits::SelectionCache::new(),
             evaluation_cache: traits::EvaluationCache::new(),
             rvalue_promotable_to_static: RefCell::new(NodeMap()),
-            fragment_infos: RefCell::new(DefIdMap()),
             crate_name: Symbol::intern(crate_name),
             data_layout: data_layout,
             layout_cache: RefCell::new(FxHashMap()),

src/librustc/ty/mod.rs

@@ -444,17 +444,6 @@ pub struct CReaderCacheKey {
     pub pos: usize,
 }
 
-/// Describes the fragment-state associated with a NodeId.
-///
-/// Currently only unfragmented paths have entries in the table,
-/// but longer-term this enum is expected to expand to also
-/// include data for fragmented paths.
-#[derive(Copy, Clone, Debug)]
-pub enum FragmentInfo {
-    Moved { var: NodeId, move_expr: NodeId },
-    Assigned { var: NodeId, assign_expr: NodeId, assignee_id: NodeId },
-}
-
 // Flags that we track on types. These flags are propagated upwards
 // through the type during type construction, so that we can quickly
 // check whether the type has various kinds of types in it without

src/librustc/ty/util.rs

@@ -266,13 +266,29 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// if not a structure at all. Corresponds to the only possible unsized
     /// field, and its type can be used to determine unsizing strategy.
     pub fn struct_tail(self, mut ty: Ty<'tcx>) -> Ty<'tcx> {
-        while let TyAdt(def, substs) = ty.sty {
-            if !def.is_struct() {
-                break;
-            }
-            match def.struct_variant().fields.last() {
-                Some(f) => ty = f.ty(self, substs),
-                None => break,
+        loop {
+            match ty.sty {
+                ty::TyAdt(def, substs) => {
+                    if !def.is_struct() {
+                        break;
+                    }
+                    match def.struct_variant().fields.last() {
+                        Some(f) => ty = f.ty(self, substs),
+                        None => break,
+                    }
+                }
+
+                ty::TyTuple(tys, _) => {
+                    if let Some((&last_ty, _)) = tys.split_last() {
+                        ty = last_ty;
+                    } else {
+                        break;
+                    }
+                }
+
+                _ => {
+                    break;
+                }
             }
         }
         ty