Auto merge of #44062 - alexcrichton:beta-next, r=alexcrichton

[beta] Final round of beta backports

Includes:

* [x] #43723
* [x] #43830
* [x] #43844
* [x] #44013
* [x] #44049
* [x] #43948

src/bootstrap/channel.rs

@@ -28,7 +28,7 @@ pub const CFG_RELEASE_NUM: &str = "1.20.0";
 // An optional number to put after the label, e.g. '.2' -> '-beta.2'
 // Be sure to make this starts with a dot to conform to semver pre-release
 // versions (section 9)
-pub const CFG_PRERELEASE_VERSION: &str = ".2";
+pub const CFG_PRERELEASE_VERSION: &str = ".3";
 
 pub struct GitInfo {
     inner: Option<Info>,

src/liballoc/allocator.rs

@@ -452,6 +452,27 @@ impl fmt::Display for CannotReallocInPlace {
 ///  * if a layout `k` fits a memory block (denoted by `ptr`)
 ///    currently allocated via an allocator `a`, then it is legal to
 ///    use that layout to deallocate it, i.e. `a.dealloc(ptr, k);`.
+///
+/// # Unsafety
+///
+/// The `Alloc` trait is an `unsafe` trait for a number of reasons, and
+/// implementors must ensure that they adhere to these contracts:
+///
+/// * Pointers returned from allocation functions must point to valid memory and
+///   retain their validity until at least the instance of `Alloc` is dropped
+///   itself.
+///
+/// * Implementations of `Alloc` are not currently memory safe if they unwind.
+///   This restriction may be lifted in the future, but currently an panic from
+///   any of these functions may lead to memory unsafety.
+///
+/// * `Layout` queries and calculations in general must be correct. Callers of
+///   this trait are allowed to rely on the contracts defined on each method,
+///   and implementors must ensure such contracts remain true.
+///
+/// Note that this list may get tweaked over time as clarifications are made in
+/// the future. Additionally global allocators may gain unique requirements for
+/// how to safely implement one in the future as well.
 pub unsafe trait Alloc {
 
     // (Note: existing allocators have unspecified but well-defined

src/liballoc/heap.rs

@@ -27,35 +27,46 @@ pub mod __core {
 
 extern "Rust" {
     #[allocator]
+    #[allocator_nounwind]
     fn __rust_alloc(size: usize, align: usize, err: *mut u8) -> *mut u8;
+    #[cold]
+    #[allocator_nounwind]
     fn __rust_oom(err: *const u8) -> !;
+    #[allocator_nounwind]
     fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
+    #[allocator_nounwind]
     fn __rust_usable_size(layout: *const u8,
                           min: *mut usize,
                           max: *mut usize);
+    #[allocator_nounwind]
     fn __rust_realloc(ptr: *mut u8,
                       old_size: usize,
                       old_align: usize,
                       new_size: usize,
                       new_align: usize,
                       err: *mut u8) -> *mut u8;
+    #[allocator_nounwind]
     fn __rust_alloc_zeroed(size: usize, align: usize, err: *mut u8) -> *mut u8;
+    #[allocator_nounwind]
     fn __rust_alloc_excess(size: usize,
                            align: usize,
                            excess: *mut usize,
                            err: *mut u8) -> *mut u8;
+    #[allocator_nounwind]
     fn __rust_realloc_excess(ptr: *mut u8,
                              old_size: usize,
                              old_align: usize,
                              new_size: usize,
                              new_align: usize,
                              excess: *mut usize,
                              err: *mut u8) -> *mut u8;
+    #[allocator_nounwind]
     fn __rust_grow_in_place(ptr: *mut u8,
                             old_size: usize,
                             old_align: usize,
                             new_size: usize,
                             new_align: usize) -> u8;
+    #[allocator_nounwind]
     fn __rust_shrink_in_place(ptr: *mut u8,
                               old_size: usize,
                               old_align: usize,

src/librustc/traits/error_reporting.rs

@@ -278,8 +278,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         let mut self_match_impls = vec![];
         let mut fuzzy_match_impls = vec![];
 
-        self.tcx.trait_def(trait_ref.def_id)
-            .for_each_relevant_impl(self.tcx, trait_self_ty, |def_id| {
+        self.tcx.for_each_relevant_impl(
+            trait_ref.def_id, trait_self_ty, |def_id| {
                 let impl_substs = self.fresh_substs_for_item(obligation.cause.span, def_id);
                 let impl_trait_ref = tcx
                     .impl_trait_ref(def_id)
@@ -396,10 +396,9 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                               trait_ref.skip_binder().self_ty(),
                                               true);
         let mut impl_candidates = Vec::new();
-        let trait_def = self.tcx.trait_def(trait_ref.def_id());
 
         match simp {
-            Some(simp) => trait_def.for_each_impl(self.tcx, |def_id| {
+            Some(simp) => self.tcx.for_each_impl(trait_ref.def_id(), |def_id| {
                 let imp = self.tcx.impl_trait_ref(def_id).unwrap();
                 let imp_simp = fast_reject::simplify_type(self.tcx,
                                                           imp.self_ty(),
@@ -411,7 +410,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 }
                 impl_candidates.push(imp);
             }),
-            None => trait_def.for_each_impl(self.tcx, |def_id| {
+            None => self.tcx.for_each_impl(trait_ref.def_id(), |def_id| {
                 impl_candidates.push(
                     self.tcx.impl_trait_ref(def_id).unwrap());
             })

src/librustc/traits/select.rs

@@ -1430,10 +1430,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     {
         debug!("assemble_candidates_from_impls(obligation={:?})", obligation);
 
-        let def = self.tcx().trait_def(obligation.predicate.def_id());
-
-        def.for_each_relevant_impl(
-            self.tcx(),
+        self.tcx().for_each_relevant_impl(
+            obligation.predicate.def_id(),
             obligation.predicate.0.trait_ref.self_ty(),
             |impl_def_id| {
                 self.probe(|this, snapshot| { /* [1] */

src/librustc/traits/specialize/mod.rs

@@ -300,7 +300,8 @@ pub(super) fn specialization_graph_provider<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx
                                                       -> Rc<specialization_graph::Graph> {
     let mut sg = specialization_graph::Graph::new();
 
-    let mut trait_impls: Vec<DefId> = tcx.trait_impls_of(trait_id).iter().collect();
+    let mut trait_impls = Vec::new();
+    tcx.for_each_impl(trait_id, |impl_did| trait_impls.push(impl_did));
 
     // The coherence checking implementation seems to rely on impls being
     // iterated over (roughly) in definition order, so we are sorting by

src/librustc/ty/maps.rs

@@ -470,12 +470,6 @@ impl<'tcx> QueryDescription for queries::trait_impls_of<'tcx> {
     }
 }
 
-impl<'tcx> QueryDescription for queries::relevant_trait_impls_for<'tcx> {
-    fn describe(tcx: TyCtxt, (def_id, ty): (DefId, SimplifiedType)) -> String {
-        format!("relevant impls for: `({}, {:?})`", tcx.item_path_str(def_id), ty)
-    }
-}
-
 impl<'tcx> QueryDescription for queries::is_object_safe<'tcx> {
     fn describe(tcx: TyCtxt, def_id: DefId) -> String {
         format!("determine object safety of trait `{}`", tcx.item_path_str(def_id))
@@ -966,10 +960,7 @@ define_maps! { <'tcx>
     [] const_is_rvalue_promotable_to_static: ConstIsRvaluePromotableToStatic(DefId) -> bool,
     [] is_mir_available: IsMirAvailable(DefId) -> bool,
 
-    [] trait_impls_of: TraitImpls(DefId) -> ty::trait_def::TraitImpls,
-    // Note that TraitDef::for_each_relevant_impl() will do type simplication for you.
-    [] relevant_trait_impls_for: relevant_trait_impls_for((DefId, SimplifiedType))
-        -> ty::trait_def::TraitImpls,
+    [] trait_impls_of: TraitImpls(DefId) -> Rc<ty::trait_def::TraitImpls>,
     [] specialization_graph_of: SpecializationGraph(DefId) -> Rc<specialization_graph::Graph>,
     [] is_object_safe: ObjectSafety(DefId) -> bool,
 
@@ -1045,10 +1036,6 @@ fn crate_variances<'tcx>(_: CrateNum) -> DepConstructor<'tcx> {
     DepConstructor::CrateVariances
 }
 
-fn relevant_trait_impls_for<'tcx>((def_id, t): (DefId, SimplifiedType)) -> DepConstructor<'tcx> {
-    DepConstructor::RelevantTraitImpls(def_id, t)
-}
-
 fn is_copy_dep_node<'tcx>(key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> DepConstructor<'tcx> {
     let def_id = ty::item_path::characteristic_def_id_of_type(key.value)
         .unwrap_or(DefId::local(CRATE_DEF_INDEX));

src/librustc/ty/mod.rs

@@ -2530,7 +2530,6 @@ pub fn provide(providers: &mut ty::maps::Providers) {
         param_env,
         trait_of_item,
         trait_impls_of: trait_def::trait_impls_of_provider,
-        relevant_trait_impls_for: trait_def::relevant_trait_impls_provider,
         ..*providers
     };
 }
@@ -2540,7 +2539,6 @@ pub fn provide_extern(providers: &mut ty::maps::Providers) {
         adt_sized_constraint,
         adt_dtorck_constraint,
         trait_impls_of: trait_def::trait_impls_of_provider,
-        relevant_trait_impls_for: trait_def::relevant_trait_impls_provider,
         param_env,
         ..*providers
     };