Auto merge of #63465 - Mark-Simulacrum:rollup-bq3u7tz, r=Mark-Simulacrum

Rollup of 8 pull requests

Successful merges:

 - #61969 (Add #[repr(transparent)] for several types)
 - #62108 (Use sharded maps for queries)
 - #63149 (resolve: Populate external modules in more automatic and lazy way)
 - #63346 (Lint on some incorrect uses of mem::zeroed / mem::uninitialized)
 - #63433 (Miri shouldn't look at types)
 - #63440 (rename RUST_CTFE_BACKTRACE to RUSTC_CTFE_BACKTRACE)
 - #63442 (Add an example to show how to insert item to a sorted vec)
 - #63459 (syntax: account for CVarArgs being in the argument list.)

Failed merges:

r? @ghost

src/libcore/mem/maybe_uninit.rs

@@ -13,6 +13,7 @@ use crate::mem::ManuallyDrop;
 /// ever gets used to access memory:
 ///
 /// ```rust,no_run
+/// # #![allow(invalid_value)]
 /// use std::mem::{self, MaybeUninit};
 ///
 /// let x: &i32 = unsafe { mem::zeroed() }; // undefined behavior!
@@ -27,6 +28,7 @@ use crate::mem::ManuallyDrop;
 /// always be `true` or `false`. Hence, creating an uninitialized `bool` is undefined behavior:
 ///
 /// ```rust,no_run
+/// # #![allow(invalid_value)]
 /// use std::mem::{self, MaybeUninit};
 ///
 /// let b: bool = unsafe { mem::uninitialized() }; // undefined behavior!
@@ -40,6 +42,7 @@ use crate::mem::ManuallyDrop;
 /// which otherwise can hold any *fixed* bit pattern:
 ///
 /// ```rust,no_run
+/// # #![allow(invalid_value)]
 /// use std::mem::{self, MaybeUninit};
 ///
 /// let x: i32 = unsafe { mem::uninitialized() }; // undefined behavior!

src/libcore/mem/mod.rs

@@ -445,7 +445,8 @@ pub const fn needs_drop<T>() -> bool {
 ///
 /// *Incorrect* usage of this function: initializing a reference with zero.
 ///
-/// ```no_run
+/// ```rust,no_run
+/// # #![allow(invalid_value)]
 /// use std::mem;
 ///
 /// let _x: &i32 = unsafe { mem::zeroed() }; // Undefined behavior!

src/libcore/slice/mod.rs

@@ -1364,6 +1364,17 @@ impl<T> [T] {
     /// let r = s.binary_search(&1);
     /// assert!(match r { Ok(1..=4) => true, _ => false, });
     /// ```
+    ///
+    /// If you want to insert an item to a sorted vector, while maintaining
+    /// sort order:
+    ///
+    /// ```
+    /// let mut s = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55];
+    /// let num = 42;
+    /// let idx = s.binary_search(&num).unwrap_or_else(|x| x);
+    /// s.insert(idx, num);
+    /// assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]);
+    /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn binary_search(&self, x: &T) -> Result<usize, usize>
         where T: Ord

src/librustc/mir/interpret/error.rs

@@ -217,7 +217,7 @@ fn print_backtrace(backtrace: &mut Backtrace) {
 
 impl<'tcx> From<InterpError<'tcx>> for InterpErrorInfo<'tcx> {
     fn from(kind: InterpError<'tcx>) -> Self {
-        let backtrace = match env::var("RUST_CTFE_BACKTRACE") {
+        let backtrace = match env::var("RUSTC_CTFE_BACKTRACE") {
             // Matching `RUST_BACKTRACE` -- we treat "0" the same as "not present".
             Ok(ref val) if val != "0" => {
                 let mut backtrace = Backtrace::new_unresolved();

src/librustc/ty/mod.rs

@@ -1842,7 +1842,8 @@ pub struct VariantDef {
     pub ctor_kind: CtorKind,
     /// Flags of the variant (e.g. is field list non-exhaustive)?
     flags: VariantFlags,
-    /// Recovered?
+    /// Variant is obtained as part of recovering from a syntactic error.
+    /// May be incomplete or bogus.
     pub recovered: bool,
 }
 
@@ -1949,7 +1950,7 @@ pub struct FieldDef {
 pub struct AdtDef {
     /// `DefId` of the struct, enum or union item.
     pub did: DefId,
-    /// Variants of the ADT. If this is a struct or enum, then there will be a single variant.
+    /// Variants of the ADT. If this is a struct or union, then there will be a single variant.
     pub variants: IndexVec<self::layout::VariantIdx, VariantDef>,
     /// Flags of the ADT (e.g. is this a struct? is this non-exhaustive?)
     flags: AdtFlags,
@@ -2565,6 +2566,8 @@ impl<'tcx> AdtDef {
 }
 
 impl<'tcx> FieldDef {
+    /// Returns the type of this field. The `subst` is typically obtained
+    /// via the second field of `TyKind::AdtDef`.
     pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
         tcx.type_of(self.did).subst(tcx, subst)
     }

src/librustc/ty/query/config.rs

@@ -11,7 +11,7 @@ use crate::util::profiling::ProfileCategory;
 use std::borrow::Cow;
 use std::hash::Hash;
 use std::fmt::Debug;
-use rustc_data_structures::sync::Lock;
+use rustc_data_structures::sharded::Sharded;
 use rustc_data_structures::fingerprint::Fingerprint;
 use crate::ich::StableHashingContext;
 
@@ -34,7 +34,7 @@ pub(crate) trait QueryAccessors<'tcx>: QueryConfig<'tcx> {
     fn query(key: Self::Key) -> Query<'tcx>;
 
     // Don't use this method to access query results, instead use the methods on TyCtxt
-    fn query_cache<'a>(tcx: TyCtxt<'tcx>) -> &'a Lock<QueryCache<'tcx, Self>>;
+    fn query_cache<'a>(tcx: TyCtxt<'tcx>) -> &'a Sharded<QueryCache<'tcx, Self>>;
 
     fn to_dep_node(tcx: TyCtxt<'tcx>, key: &Self::Key) -> DepNode;
 

src/librustc/ty/query/on_disk_cache.rs

@@ -1062,9 +1062,9 @@ where
         ::std::any::type_name::<Q>());
 
     time_ext(tcx.sess.time_extended(), Some(tcx.sess), desc, || {
-        let map = Q::query_cache(tcx).borrow();
-        assert!(map.active.is_empty());
-        for (key, entry) in map.results.iter() {
+        let shards = Q::query_cache(tcx).lock_shards();
+        assert!(shards.iter().all(|shard| shard.active.is_empty()));
+        for (key, entry) in shards.iter().flat_map(|shard| shard.results.iter()) {
             if Q::cache_on_disk(tcx, key.clone(), Some(&entry.value)) {
                 let dep_node = SerializedDepNodeIndex::new(entry.index.index());
 

src/librustc/ty/query/plumbing.rs

@@ -17,6 +17,7 @@ use errors::Diagnostic;
 use errors::FatalError;
 use rustc_data_structures::fx::{FxHashMap};
 use rustc_data_structures::sync::{Lrc, Lock};
+use rustc_data_structures::sharded::Sharded;
 use rustc_data_structures::thin_vec::ThinVec;
 #[cfg(not(parallel_compiler))]
 use rustc_data_structures::cold_path;
@@ -90,7 +91,7 @@ macro_rules! profq_query_msg {
 /// A type representing the responsibility to execute the job in the `job` field.
 /// This will poison the relevant query if dropped.
 pub(super) struct JobOwner<'a, 'tcx, Q: QueryDescription<'tcx>> {
-    cache: &'a Lock<QueryCache<'tcx, Q>>,
+    cache: &'a Sharded<QueryCache<'tcx, Q>>,
     key: Q::Key,
     job: Lrc<QueryJob<'tcx>>,
 }
@@ -107,7 +108,7 @@ impl<'a, 'tcx, Q: QueryDescription<'tcx>> JobOwner<'a, 'tcx, Q> {
     pub(super) fn try_get(tcx: TyCtxt<'tcx>, span: Span, key: &Q::Key) -> TryGetJob<'a, 'tcx, Q> {
         let cache = Q::query_cache(tcx);
         loop {
-            let mut lock = cache.borrow_mut();
+            let mut lock = cache.get_shard_by_value(key).lock();
             if let Some(value) = lock.results.get(key) {
                 profq_msg!(tcx, ProfileQueriesMsg::CacheHit);
                 tcx.sess.profiler(|p| p.record_query_hit(Q::NAME));
@@ -191,7 +192,7 @@ impl<'a, 'tcx, Q: QueryDescription<'tcx>> JobOwner<'a, 'tcx, Q> {
 
         let value = QueryValue::new(result.clone(), dep_node_index);
         {
-            let mut lock = cache.borrow_mut();
+            let mut lock = cache.get_shard_by_value(&key).lock();
             lock.active.remove(&key);
             lock.results.insert(key, value);
         }
@@ -215,7 +216,8 @@ impl<'a, 'tcx, Q: QueryDescription<'tcx>> Drop for JobOwner<'a, 'tcx, Q> {
     #[cold]
     fn drop(&mut self) {
         // Poison the query so jobs waiting on it panic
-        self.cache.borrow_mut().active.insert(self.key.clone(), QueryResult::Poisoned);
+        let shard = self.cache.get_shard_by_value(&self.key);
+        shard.lock().active.insert(self.key.clone(), QueryResult::Poisoned);
         // Also signal the completion of the job, so waiters
         // will continue execution
         self.job.signal_complete();
@@ -708,7 +710,7 @@ macro_rules! define_queries_inner {
         use std::mem;
         #[cfg(parallel_compiler)]
         use ty::query::job::QueryResult;
-        use rustc_data_structures::sync::Lock;
+        use rustc_data_structures::sharded::Sharded;
         use crate::{
             rustc_data_structures::stable_hasher::HashStable,
             rustc_data_structures::stable_hasher::StableHasherResult,
@@ -740,18 +742,17 @@ macro_rules! define_queries_inner {
             pub fn collect_active_jobs(&self) -> Vec<Lrc<QueryJob<$tcx>>> {
                 let mut jobs = Vec::new();
 
-                // We use try_lock here since we are only called from the
+                // We use try_lock_shards here since we are only called from the
                 // deadlock handler, and this shouldn't be locked.
                 $(
-                    jobs.extend(
-                        self.$name.try_lock().unwrap().active.values().filter_map(|v|
-                            if let QueryResult::Started(ref job) = *v {
-                                Some(job.clone())
-                            } else {
-                                None
-                            }
-                        )
-                    );
+                    let shards = self.$name.try_lock_shards().unwrap();
+                    jobs.extend(shards.iter().flat_map(|shard| shard.active.values().filter_map(|v|
+                        if let QueryResult::Started(ref job) = *v {
+                            Some(job.clone())
+                        } else {
+                            None
+                        }
+                    )));
                 )*
 
                 jobs
@@ -773,26 +774,27 @@ macro_rules! define_queries_inner {
 
                 fn stats<'tcx, Q: QueryConfig<'tcx>>(
                     name: &'static str,
-                    map: &QueryCache<'tcx, Q>
+                    map: &Sharded<QueryCache<'tcx, Q>>,
                 ) -> QueryStats {
+                    let map = map.lock_shards();
                     QueryStats {
                         name,
                         #[cfg(debug_assertions)]
-                        cache_hits: map.cache_hits,
+                        cache_hits: map.iter().map(|shard| shard.cache_hits).sum(),
                         #[cfg(not(debug_assertions))]
                         cache_hits: 0,
                         key_size: mem::size_of::<Q::Key>(),
                         key_type: type_name::<Q::Key>(),
                         value_size: mem::size_of::<Q::Value>(),
                         value_type: type_name::<Q::Value>(),
-                        entry_count: map.results.len(),
+                        entry_count: map.iter().map(|shard| shard.results.len()).sum(),
                     }
                 }
 
                 $(
                     queries.push(stats::<queries::$name<'_>>(
                         stringify!($name),
-                        &*self.$name.lock()
+                        &self.$name,
                     ));
                 )*
 
@@ -967,7 +969,7 @@ macro_rules! define_queries_inner {
             }
 
             #[inline(always)]
-            fn query_cache<'a>(tcx: TyCtxt<$tcx>) -> &'a Lock<QueryCache<$tcx, Self>> {
+            fn query_cache<'a>(tcx: TyCtxt<$tcx>) -> &'a Sharded<QueryCache<$tcx, Self>> {
                 &tcx.queries.$name
             }
 
@@ -1099,7 +1101,7 @@ macro_rules! define_queries_struct {
             providers: IndexVec<CrateNum, Providers<$tcx>>,
             fallback_extern_providers: Box<Providers<$tcx>>,
 
-            $($(#[$attr])*  $name: Lock<QueryCache<$tcx, queries::$name<$tcx>>>,)*
+            $($(#[$attr])*  $name: Sharded<QueryCache<$tcx, queries::$name<$tcx>>>,)*
         }
     };
 }

src/librustc/ty/sty.rs

@@ -171,6 +171,7 @@ pub enum TyKind<'tcx> {
     Never,
 
     /// A tuple type. For example, `(i32, bool)`.
+    /// Use `TyS::tuple_fields` to iterate over the field types.
     Tuple(SubstsRef<'tcx>),
 
     /// The projection of an associated type. For example,
@@ -1723,8 +1724,8 @@ impl<'tcx> TyS<'tcx> {
                     })
                 })
             }
-            ty::Tuple(tys) => tys.iter().any(|ty| {
-                ty.expect_ty().conservative_is_privately_uninhabited(tcx)
+            ty::Tuple(..) => self.tuple_fields().any(|ty| {
+                ty.conservative_is_privately_uninhabited(tcx)
             }),
             ty::Array(ty, len) => {
                 match len.try_eval_usize(tcx, ParamEnv::empty()) {
@@ -2103,6 +2104,15 @@ impl<'tcx> TyS<'tcx> {
         }
     }
 
+    /// Iterates over tuple fields.
+    /// Panics when called on anything but a tuple.
+    pub fn tuple_fields(&self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> {
+        match self.sty {
+            Tuple(substs) => substs.iter().map(|field| field.expect_ty()),
+            _ => bug!("tuple_fields called on non-tuple"),
+        }
+    }
+
     /// If the type contains variants, returns the valid range of variant indices.
     /// FIXME This requires the optimized MIR in the case of generators.
     #[inline]

src/librustc/ty/util.rs

@@ -845,15 +845,15 @@ impl<'tcx> ty::TyS<'tcx> {
             ty: Ty<'tcx>,
         ) -> Representability {
             match ty.sty {
-                Tuple(ref ts) => {
+                Tuple(..) => {
                     // Find non representable
-                    fold_repr(ts.iter().map(|ty| {
+                    fold_repr(ty.tuple_fields().map(|ty| {
                         is_type_structurally_recursive(
                             tcx,
                             sp,
                             seen,
                             representable_cache,
-                            ty.expect_ty(),
+                            ty,
                         )
                     }))
                 }
@@ -1095,7 +1095,7 @@ fn needs_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>
         // state transformation pass
         ty::Generator(..) => true,
 
-        ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).any(needs_drop),
+        ty::Tuple(..) => ty.tuple_fields().any(needs_drop),
 
         // unions don't have destructors because of the child types,
         // only if they manually implement `Drop` (handled above).

src/librustc/ty/walk.rs

@@ -119,8 +119,8 @@ fn push_subtypes<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent_ty: Ty<'tcx>) {
         ty::GeneratorWitness(ts) => {
             stack.extend(ts.skip_binder().iter().cloned().rev());
         }
-        ty::Tuple(ts) => {
-            stack.extend(ts.iter().map(|k| k.expect_ty()).rev());
+        ty::Tuple(..) => {
+            stack.extend(parent_ty.tuple_fields().rev());
         }
         ty::FnDef(_, substs) => {
             stack.extend(substs.types().rev());