Auto merge of #66436 - JohnTitor:rollup-kphyb2i, r=JohnTitor

Rollup of 12 pull requests

Successful merges:

 - #65557 (rename Error::iter_chain() and remove Error::iter_sources())
 - #66013 (Avoid hashing the key twice in `get_query()`.)
 - #66306 (Remove cannot mutate statics in initializer of another static error)
 - #66338 (Update mdbook.)
 - #66388 (Do not ICE on recovery from unmet associated type bound obligation)
 - #66390 (Fix ICE when trying to suggest `Type<>` instead of `Type()`)
 - #66391 (Do not ICE in `if` without `else` in `async fn`)
 - #66394 (Fix two OOM issues related to `ConstProp`)
 - #66398 (Remove some stack frames from `.async` calls)
 - #66410 (miri: helper methods for max values of machine's usize/isize)
 - #66418 (Link to tracking issue in HIR const-check error code description)
 - #66419 (Don't warn labels beginning with `_` on unused_labels lint)

Failed merges:

r? @ghost

Author: bors

Cargo.lock

@@ -1862,15 +1862,16 @@ impl<'a> LoweringContext<'a> {
                         if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
                             // Do not suggest going from `Trait()` to `Trait<>`
                             if data.inputs.len() > 0 {
-                                let split = snippet.find('(').unwrap();
-                                let trait_name = &snippet[0..split];
-                                let args = &snippet[split + 1 .. snippet.len() - 1];
-                                err.span_suggestion(
-                                    data.span,
-                                    "use angle brackets instead",
-                                    format!("{}<{}>", trait_name, args),
-                                    Applicability::MaybeIncorrect,
-                                );
+                                if let Some(split) = snippet.find('(') {
+                                    let trait_name = &snippet[0..split];
+                                    let args = &snippet[split + 1 .. snippet.len() - 1];
+                                    err.span_suggestion(
+                                        data.span,
+                                        "use angle brackets instead",
+                                        format!("{}<{}>", trait_name, args),
+                                        Applicability::MaybeIncorrect,
+                                    );
+                                }
                             }
                         };
                         err.emit();

src/librustc/hir/lowering.rs

@@ -59,6 +59,7 @@
 #![feature(log_syntax)]
 #![feature(associated_type_bounds)]
 #![feature(rustc_attrs)]
+#![feature(hash_raw_entry)]
 
 #![recursion_limit="512"]
 

src/librustc/lib.rs

@@ -1,4 +1,5 @@
 use std::fmt::{self, Display};
+use std::convert::TryFrom;
 
 use crate::mir;
 use crate::ty::layout::{self, HasDataLayout, Size};
@@ -40,6 +41,18 @@ pub trait PointerArithmetic: layout::HasDataLayout {
         self.data_layout().pointer_size
     }
 
+    #[inline]
+    fn usize_max(&self) -> u64 {
+        let max_usize_plus_1 = 1u128 << self.pointer_size().bits();
+        u64::try_from(max_usize_plus_1-1).unwrap()
+    }
+
+    #[inline]
+    fn isize_max(&self) -> i64 {
+        let max_isize_plus_1 = 1u128 << (self.pointer_size().bits()-1);
+        i64::try_from(max_isize_plus_1-1).unwrap()
+    }
+
     /// Helper function: truncate given value-"overflowed flag" pair to pointer size and
     /// update "overflowed flag" if there was an overflow.
     /// This should be called by all the other methods before returning!

src/librustc/mir/interpret/pointer.rs

@@ -14,12 +14,13 @@ use errors::Level;
 use errors::Diagnostic;
 use errors::FatalError;
 use errors::Handler;
-use rustc_data_structures::fx::{FxHashMap};
+use rustc_data_structures::fx::{FxHasher, 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;
+use std::hash::{Hash, Hasher};
 use std::mem;
 use std::ptr;
 use std::collections::hash_map::Entry;
@@ -82,8 +83,17 @@ 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.get_shard_by_value(key).lock();
-            if let Some(value) = lock.results.get(key) {
+            // We compute the key's hash once and then use it for both the
+            // shard lookup and the hashmap lookup. This relies on the fact
+            // that both of them use `FxHasher`.
+            let mut state = FxHasher::default();
+            key.hash(&mut state);
+            let key_hash = state.finish();
+
+            let mut lock = cache.get_shard_by_hash(key_hash).lock();
+            if let Some((_, value)) =
+                lock.results.raw_entry().from_key_hashed_nocheck(key_hash, key)
+            {
                 tcx.prof.query_cache_hit(Q::NAME);
                 let result = (value.value.clone(), value.index);
                 #[cfg(debug_assertions)]

src/librustc/ty/query/plumbing.rs

@@ -60,6 +60,7 @@ impl<T> Sharded<T> {
         }
     }
 
+    /// The shard is selected by hashing `val` with `FxHasher`.
     #[inline]
     pub fn get_shard_by_value<K: Hash + ?Sized>(&self, val: &K) -> &Lock<T> {
         if SHARDS == 1 {
@@ -69,6 +70,11 @@ impl<T> Sharded<T> {
         }
     }
 
+    /// Get a shard with a pre-computed hash value. If `get_shard_by_value` is
+    /// ever used in combination with `get_shard_by_hash` on a single `Sharded`
+    /// instance, then `hash` must be computed with `FxHasher`. Otherwise,
+    /// `hash` can be computed with any hasher, so long as that hasher is used
+    /// consistently for each `Sharded` instance.
     #[inline]
     pub fn get_shard_by_hash(&self, hash: u64) -> &Lock<T> {
         let hash_len = mem::size_of::<usize>();

src/librustc_data_structures/sharded.rs

@@ -15,3 +15,10 @@ const _: i32 = {
     x
 };
 ```
+
+This will be allowed at some point in the future, but the implementation is not
+yet complete. See the tracking issue for [conditionals] or [loops] in a const
+context for the current status.
+
+[conditionals]: https://github.com/rust-lang/rust/issues/49146
+[loops]: https://github.com/rust-lang/rust/issues/52000

src/librustc_error_codes/error_codes/E0744.md

@@ -326,17 +326,7 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
                 let is_thread_local = self.tcx.has_attr(*def_id, sym::thread_local);
                 if is_thread_local {
                     self.check_op(ops::ThreadLocalAccess);
-                } else if self.const_kind() == ConstKind::Static && context.is_mutating_use() {
-                    // this is not strictly necessary as miri will also bail out
-                    // For interior mutability we can't really catch this statically as that
-                    // goes through raw pointers and intermediate temporaries, so miri has
-                    // to catch this anyway
-
-                    self.tcx.sess.span_err(
-                        self.span,
-                        "cannot mutate statics in the initializer of another static",
-                    );
-                } else {
+                } else if self.const_kind() != ConstKind::Static || !context.is_mutating_use() {
                     self.check_op(ops::StaticAccess);
                 }
             }

src/librustc_mir/transform/check_consts/validation.rs

@@ -22,7 +22,7 @@ use rustc::ty::subst::InternalSubsts;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_index::vec::IndexVec;
 use rustc::ty::layout::{
-    LayoutOf, TyLayout, LayoutError, HasTyCtxt, TargetDataLayout, HasDataLayout,
+    LayoutOf, TyLayout, LayoutError, HasTyCtxt, TargetDataLayout, HasDataLayout, Size,
 };
 
 use crate::rustc::ty::subst::Subst;
@@ -35,6 +35,9 @@ use crate::interpret::{
 use crate::const_eval::error_to_const_error;
 use crate::transform::{MirPass, MirSource};
 
+/// The maximum number of bytes that we'll allocate space for a return value.
+const MAX_ALLOC_LIMIT: u64 = 1024;
+
 pub struct ConstProp;
 
 impl<'tcx> MirPass<'tcx> for ConstProp {
@@ -313,8 +316,10 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             ecx
                 .layout_of(body.return_ty().subst(tcx, substs))
                 .ok()
-                // Don't bother allocating memory for ZST types which have no values.
-                .filter(|ret_layout| !ret_layout.is_zst())
+                // Don't bother allocating memory for ZST types which have no values
+                // or for large values.
+                .filter(|ret_layout| !ret_layout.is_zst() &&
+                                     ret_layout.size < Size::from_bytes(MAX_ALLOC_LIMIT))
                 .map(|ret_layout| ecx.allocate(ret_layout, MemoryKind::Stack));
 
         ecx.push_stack_frame(
@@ -453,6 +458,11 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
     ) -> Option<()> {
         let span = source_info.span;
 
+        // #66397: Don't try to eval into large places as that can cause an OOM
+        if place_layout.size >= Size::from_bytes(MAX_ALLOC_LIMIT) {
+            return None;
+        }
+
         let overflow_check = self.tcx.sess.overflow_checks();
 
         // Perform any special handling for specific Rvalue types.

src/librustc_mir/transform/const_prop.rs

@@ -787,19 +787,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
 
                 // Only allow statics (not consts) to refer to other statics.
                 if self.mode == Mode::Static || self.mode == Mode::StaticMut {
-                    if self.mode == Mode::Static
-                        && context.is_mutating_use()
-                        && !self.suppress_errors
-                    {
-                        // this is not strictly necessary as miri will also bail out
-                        // For interior mutability we can't really catch this statically as that
-                        // goes through raw pointers and intermediate temporaries, so miri has
-                        // to catch this anyway
-                        self.tcx.sess.span_err(
-                            self.span,
-                            "cannot mutate statics in the initializer of another static",
-                        );
-                    }
                     return;
                 }
                 unleash_miri!(self);

src/librustc_mir/transform/qualify_consts.rs

@@ -1767,7 +1767,9 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
 
     fn with_resolved_label(&mut self, label: Option<Label>, id: NodeId, f: impl FnOnce(&mut Self)) {
         if let Some(label) = label {
-            self.diagnostic_metadata.unused_labels.insert(id, label.ident.span);
+            if label.ident.as_str().as_bytes()[1] != b'_' {
+                self.diagnostic_metadata.unused_labels.insert(id, label.ident.span);
+            }
             self.with_label_rib(NormalRibKind, |this| {
                 let ident = label.ident.modern_and_legacy();
                 this.label_ribs.last_mut().unwrap().bindings.insert(ident, id);

src/librustc_resolve/late.rs

@@ -244,7 +244,13 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
         // can be reborrowed without needing to spill to a temporary.
         // If this were not the case, then we could conceivably have
         // to create intermediate temporaries.)
-        let ty = self.fcx.tables.borrow().expr_ty(expr);
-        self.record(ty, scope, Some(expr), expr.span);
+        //
+        // The type table might not have information for this expression
+        // if it is in a malformed scope. (#66387)
+        if let Some(ty) = self.fcx.tables.borrow().expr_ty_opt(expr) {
+            self.record(ty, scope, Some(expr), expr.span);
+        } else {
+            self.fcx.tcx.sess.delay_span_bug(expr.span, "no type for node");
+        }
     }
 }

src/librustc_typeck/check/generator_interior.rs

@@ -3108,7 +3108,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         fallback_has_occurred: bool,
         mutate_fullfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
     ) {
-        if let Err(mut errors) = self.fulfillment_cx.borrow_mut().select_where_possible(self) {
+        let result = self.fulfillment_cx.borrow_mut().select_where_possible(self);
+        if let Err(mut errors) = result {
             mutate_fullfillment_errors(&mut errors);
             self.report_fulfillment_errors(&errors, self.inh.body_id, fallback_has_occurred);
         }

src/librustc_typeck/check/mod.rs

@@ -725,6 +725,9 @@ impl dyn Error {
     /// Returns an iterator starting with the current error and continuing with
     /// recursively calling [`source`].
     ///
+    /// If you want to omit the current error and only use its sources,
+    /// use `skip(1)`.
+    ///
     /// # Examples
     ///
     /// ```
@@ -763,7 +766,7 @@ impl dyn Error {
     /// // let err : Box<Error> = b.into(); // or
     /// let err = &b as &(dyn Error);
     ///
-    /// let mut iter = err.iter_chain();
+    /// let mut iter = err.chain();
     ///
     /// assert_eq!("B".to_string(), iter.next().unwrap().to_string());
     /// assert_eq!("A".to_string(), iter.next().unwrap().to_string());
@@ -774,98 +777,27 @@ impl dyn Error {
     /// [`source`]: trait.Error.html#method.source
     #[unstable(feature = "error_iter", issue = "58520")]
     #[inline]
-    pub fn iter_chain(&self) -> ErrorIter<'_> {
-        ErrorIter {
+    pub fn chain(&self) -> Chain<'_> {
+        Chain {
             current: Some(self),
         }
     }
-
-    /// Returns an iterator starting with the [`source`] of this error
-    /// and continuing with recursively calling [`source`].
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(error_iter)]
-    /// use std::error::Error;
-    /// use std::fmt;
-    ///
-    /// #[derive(Debug)]
-    /// struct A;
-    ///
-    /// #[derive(Debug)]
-    /// struct B(Option<Box<dyn Error + 'static>>);
-    ///
-    /// #[derive(Debug)]
-    /// struct C(Option<Box<dyn Error + 'static>>);
-    ///
-    /// impl fmt::Display for A {
-    ///     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    ///         write!(f, "A")
-    ///     }
-    /// }
-    ///
-    /// impl fmt::Display for B {
-    ///     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    ///         write!(f, "B")
-    ///     }
-    /// }
-    ///
-    /// impl fmt::Display for C {
-    ///     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    ///         write!(f, "C")
-    ///     }
-    /// }
-    ///
-    /// impl Error for A {}
-    ///
-    /// impl Error for B {
-    ///     fn source(&self) -> Option<&(dyn Error + 'static)> {
-    ///         self.0.as_ref().map(|e| e.as_ref())
-    ///     }
-    /// }
-    ///
-    /// impl Error for C {
-    ///     fn source(&self) -> Option<&(dyn Error + 'static)> {
-    ///         self.0.as_ref().map(|e| e.as_ref())
-    ///     }
-    /// }
-    ///
-    /// let b = B(Some(Box::new(A)));
-    /// let c = C(Some(Box::new(b)));
-    ///
-    /// // let err : Box<Error> = c.into(); // or
-    /// let err = &c as &(dyn Error);
-    ///
-    /// let mut iter = err.iter_sources();
-    ///
-    /// assert_eq!("B".to_string(), iter.next().unwrap().to_string());
-    /// assert_eq!("A".to_string(), iter.next().unwrap().to_string());
-    /// assert!(iter.next().is_none());
-    /// assert!(iter.next().is_none());
-    /// ```
-    ///
-    /// [`source`]: trait.Error.html#method.source
-    #[inline]
-    #[unstable(feature = "error_iter", issue = "58520")]
-    pub fn iter_sources(&self) -> ErrorIter<'_> {
-        ErrorIter {
-            current: self.source(),
-        }
-    }
 }
 
-/// An iterator over [`Error`]
+/// An iterator over an [`Error`] and its sources.
+///
+/// If you want to omit the initial error and only process
+/// its sources, use `skip(1)`.
 ///
 /// [`Error`]: trait.Error.html
 #[unstable(feature = "error_iter", issue = "58520")]
 #[derive(Copy, Clone, Debug)]
-pub struct ErrorIter<'a> {
+pub struct Chain<'a> {
     current: Option<&'a (dyn Error + 'static)>,
 }
 
 #[unstable(feature = "error_iter", issue = "58520")]
-impl<'a> Iterator for ErrorIter<'a> {
+impl<'a> Iterator for Chain<'a> {
     type Item = &'a (dyn Error + 'static);
 
     fn next(&mut self) -> Option<Self::Item> {