Auto merge of #61201 - Centril:rollup-975knrk, r=Centril

Rollup of 9 pull requests

Successful merges:

 - #61087 (Tweak `self` arg not as first argument of a method diagnostic)
 - #61114 (Vec: avoid creating slices to the elements)
 - #61144 (Suggest borrowing for loop head on move error)
 - #61149 (Fix spelling in release notes)
 - #61161 (MaybeUninit doctest: remove unnecessary type ascription)
 - #61173 (Auto-derive Encode and Decode implementations of DefPathTable)
 - #61184 (Add additional trace statements to the const propagator)
 - #61189 (Turn turbo 🐟 🍨 into an error)
 - #61193 (Add comment to explain why we change the layout for Projection)

Failed merges:

r? @ghost

RELEASES.md

@@ -157,7 +157,7 @@ Libraries
   produce a warning if their returning type is unused.
 - [The methods `checked_pow`, `saturating_pow`, `wrapping_pow`, and
   `overflowing_pow` are now available for all numeric types.][57873] These are
-  equivalvent to methods such as `wrapping_add` for the `pow` operation.
+  equivalent to methods such as `wrapping_add` for the `pow` operation.
 
 
 Stabilized APIs

src/liballoc/tests/vec.rs

@@ -1152,3 +1152,24 @@ fn test_try_reserve_exact() {
     }
 
 }
+
+#[test]
+fn test_stable_push_pop() {
+    // Test that, if we reserved enough space, adding and removing elements does not
+    // invalidate references into the vector (such as `v0`).  This test also
+    // runs in Miri, which would detect such problems.
+    let mut v = Vec::with_capacity(10);
+    v.push(13);
+
+    // laundering the lifetime -- we take care that `v` does not reallocate, so that's okay.
+    let v0 = unsafe { &*(&v[0] as *const _) };
+
+    // Now do a bunch of things and occasionally use `v0` again to assert it is still valid.
+    v.push(1);
+    v.push(2);
+    v.insert(1, 1);
+    assert_eq!(*v0, 13);
+    v.remove(1);
+    v.pop().unwrap();
+    assert_eq!(*v0, 13);
+}

src/liballoc/vec.rs

@@ -735,6 +735,75 @@ impl<T> Vec<T> {
         self
     }
 
+    /// Returns a raw pointer to the vector's buffer.
+    ///
+    /// The caller must ensure that the vector outlives the pointer this
+    /// function returns, or else it will end up pointing to garbage.
+    /// Modifying the vector may cause its buffer to be reallocated,
+    /// which would also make any pointers to it invalid.
+    ///
+    /// The caller must also ensure that the memory the pointer (non-transitively) points to
+    /// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer
+    /// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let x = vec![1, 2, 4];
+    /// let x_ptr = x.as_ptr();
+    ///
+    /// unsafe {
+    ///     for i in 0..x.len() {
+    ///         assert_eq!(*x_ptr.add(i), 1 << i);
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// [`as_mut_ptr`]: #method.as_mut_ptr
+    #[stable(feature = "vec_as_ptr", since = "1.37.0")]
+    #[inline]
+    pub fn as_ptr(&self) -> *const T {
+        // We shadow the slice method of the same name to avoid going through
+        // `deref`, which creates an intermediate reference.
+        let ptr = self.buf.ptr();
+        unsafe { assume(!ptr.is_null()); }
+        ptr
+    }
+
+    /// Returns an unsafe mutable pointer to the vector's buffer.
+    ///
+    /// The caller must ensure that the vector outlives the pointer this
+    /// function returns, or else it will end up pointing to garbage.
+    /// Modifying the vector may cause its buffer to be reallocated,
+    /// which would also make any pointers to it invalid.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// // Allocate vector big enough for 4 elements.
+    /// let size = 4;
+    /// let mut x: Vec<i32> = Vec::with_capacity(size);
+    /// let x_ptr = x.as_mut_ptr();
+    ///
+    /// // Initialize elements via raw pointer writes, then set length.
+    /// unsafe {
+    ///     for i in 0..size {
+    ///         *x_ptr.add(i) = i as i32;
+    ///     }
+    ///     x.set_len(size);
+    /// }
+    /// assert_eq!(&*x, &[0,1,2,3]);
+    /// ```
+    #[stable(feature = "vec_as_ptr", since = "1.37.0")]
+    #[inline]
+    pub fn as_mut_ptr(&mut self) -> *mut T {
+        // We shadow the slice method of the same name to avoid going through
+        // `deref_mut`, which creates an intermediate reference.
+        let ptr = self.buf.ptr();
+        unsafe { assume(!ptr.is_null()); }
+        ptr
+    }
+
     /// Forces the length of the vector to `new_len`.
     ///
     /// This is a low-level operation that maintains none of the normal
@@ -1706,9 +1775,7 @@ impl<T> ops::Deref for Vec<T> {
 
     fn deref(&self) -> &[T] {
         unsafe {
-            let p = self.buf.ptr();
-            assume(!p.is_null());
-            slice::from_raw_parts(p, self.len)
+            slice::from_raw_parts(self.as_ptr(), self.len)
         }
     }
 }
@@ -1717,9 +1784,7 @@ impl<T> ops::Deref for Vec<T> {
 impl<T> ops::DerefMut for Vec<T> {
     fn deref_mut(&mut self) -> &mut [T] {
         unsafe {
-            let ptr = self.buf.ptr();
-            assume(!ptr.is_null());
-            slice::from_raw_parts_mut(ptr, self.len)
+            slice::from_raw_parts_mut(self.as_mut_ptr(), self.len)
         }
     }
 }
@@ -1754,7 +1819,6 @@ impl<T> IntoIterator for Vec<T> {
     fn into_iter(mut self) -> IntoIter<T> {
         unsafe {
             let begin = self.as_mut_ptr();
-            assume(!begin.is_null());
             let end = if mem::size_of::<T>() == 0 {
                 arith_offset(begin as *const i8, self.len() as isize) as *const T
             } else {

src/libcore/mem.rs

@@ -982,7 +982,7 @@ impl<T: ?Sized> DerefMut for ManuallyDrop<T> {
 ///     out.write(vec![1, 2, 3]);
 /// }
 ///
-/// let mut v: MaybeUninit<Vec<i32>> = MaybeUninit::uninit();
+/// let mut v = MaybeUninit::uninit();
 /// unsafe { make_vec(v.as_mut_ptr()); }
 /// // Now we know `v` is initialized! This also makes sure the vector gets
 /// // properly dropped.
@@ -1071,7 +1071,7 @@ impl<T: ?Sized> DerefMut for ManuallyDrop<T> {
 /// optimizations, potentially resulting in a larger size:
 ///
 /// ```rust
-/// # use std::mem::{MaybeUninit, size_of, align_of};
+/// # use std::mem::{MaybeUninit, size_of};
 /// assert_eq!(size_of::<Option<bool>>(), 1);
 /// assert_eq!(size_of::<Option<MaybeUninit<bool>>>(), 2);
 /// ```

src/librustc/hir/map/definitions.rs

@@ -10,7 +10,6 @@ use crate::ich::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::indexed_vec::{IndexVec};
 use rustc_data_structures::stable_hasher::StableHasher;
-use serialize::{Encodable, Decodable, Encoder, Decoder};
 use crate::session::CrateDisambiguator;
 use std::borrow::Borrow;
 use std::fmt::Write;
@@ -25,14 +24,13 @@ use crate::util::nodemap::NodeMap;
 /// Internally the DefPathTable holds a tree of DefKeys, where each DefKey
 /// stores the DefIndex of its parent.
 /// There is one DefPathTable for each crate.
-#[derive(Clone, Default)]
+#[derive(Clone, Default, RustcDecodable, RustcEncodable)]
 pub struct DefPathTable {
     index_to_key: Vec<DefKey>,
     def_path_hashes: Vec<DefPathHash>,
 }
 
 impl DefPathTable {
-
     fn allocate(&mut self,
                 key: DefKey,
                 def_path_hash: DefPathHash)
@@ -86,28 +84,6 @@ impl DefPathTable {
     }
 }
 
-
-impl Encodable for DefPathTable {
-    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
-        // Index to key
-        self.index_to_key.encode(s)?;
-
-        // DefPath hashes
-        self.def_path_hashes.encode(s)?;
-
-        Ok(())
-    }
-}
-
-impl Decodable for DefPathTable {
-    fn decode<D: Decoder>(d: &mut D) -> Result<DefPathTable, D::Error> {
-        Ok(DefPathTable {
-            index_to_key: Decodable::decode(d)?,
-            def_path_hashes : Decodable::decode(d)?,
-        })
-    }
-}
-
 /// The definition table containing node definitions.
 /// It holds the `DefPathTable` for local `DefId`s/`DefPath`s and it also stores a
 /// mapping from `NodeId`s to local `DefId`s.

src/librustc_mir/borrow_check/conflict_errors.rs

@@ -158,18 +158,6 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                         span,
                         format!("value moved{} here, in previous iteration of loop", move_msg),
                     );
-                    if Some(CompilerDesugaringKind::ForLoop) == span.compiler_desugaring_kind() {
-                        if let Ok(snippet) = self.infcx.tcx.sess.source_map()
-                            .span_to_snippet(span)
-                        {
-                            err.span_suggestion(
-                                move_span,
-                                "consider borrowing this to avoid moving it into the for loop",
-                                format!("&{}", snippet),
-                                Applicability::MaybeIncorrect,
-                            );
-                        }
-                    }
                     is_loop_move = true;
                 } else if move_site.traversed_back_edge {
                     err.span_label(
@@ -185,7 +173,17 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                         &mut err,
                         format!("variable moved due to use{}", move_spans.describe()),
                     );
-                };
+                }
+                if Some(CompilerDesugaringKind::ForLoop) == move_span.compiler_desugaring_kind() {
+                    if let Ok(snippet) = self.infcx.tcx.sess.source_map().span_to_snippet(span) {
+                        err.span_suggestion(
+                            move_span,
+                            "consider borrowing to avoid moving into the for loop",
+                            format!("&{}", snippet),
+                            Applicability::MaybeIncorrect,
+                        );
+                    }
+                }
             }
 
             use_spans.var_span_label(

src/librustc_mir/interpret/operand.rs

@@ -475,6 +475,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> InterpretCx<'a, 'mir, 'tcx, M>
                 PlaceBase::Local(mir::RETURN_PLACE) => return err!(ReadFromReturnPointer),
                 PlaceBase::Local(local) => {
                     // FIXME use place_projection.is_empty() when is available
+                    // Do not use the layout passed in as argument if the base we are looking at
+                    // here is not the entire place.
                     let layout = if let Place::Base(_) = mir_place {
                         layout
                     } else {

src/librustc_mir/transform/const_prop.rs

@@ -295,6 +295,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
     }
 
     fn eval_place(&mut self, place: &Place<'tcx>, source_info: SourceInfo) -> Option<Const<'tcx>> {
+        trace!("eval_place(place={:?})", place);
         match *place {
             Place::Base(PlaceBase::Local(loc)) => self.places[loc].clone(),
             Place::Projection(ref proj) => match proj.elem {
@@ -516,6 +517,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
     }
 
     fn replace_with_const(&self, rval: &mut Rvalue<'tcx>, value: Const<'tcx>, span: Span) {
+        trace!("attepting to replace {:?} with {:?}", rval, value);
         self.ecx.validate_operand(
             value,
             vec![],
@@ -579,6 +581,10 @@ impl CanConstProp {
             // FIXME(oli-obk): lint variables until they are used in a condition
             // FIXME(oli-obk): lint if return value is constant
             *val = mir.local_kind(local) == LocalKind::Temp;
+
+            if !*val {
+                trace!("local {:?} can't be propagated because it's not a temporary", local);
+            }
         }
         cpv.visit_mir(mir);
         cpv.can_const_prop
@@ -598,6 +604,7 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
             // FIXME(oli-obk): we could be more powerful here, if the multiple writes
             // only occur in independent execution paths
             MutatingUse(MutatingUseContext::Store) => if self.found_assignment[local] {
+                trace!("local {:?} can't be propagated because of multiple assignments", local);
                 self.can_const_prop[local] = false;
             } else {
                 self.found_assignment[local] = true
@@ -609,7 +616,10 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
             NonMutatingUse(NonMutatingUseContext::Projection) |
             MutatingUse(MutatingUseContext::Projection) |
             NonUse(_) => {},
-            _ => self.can_const_prop[local] = false,
+            _ => {
+                trace!("local {:?} can't be propagaged because it's used: {:?}", local, context);
+                self.can_const_prop[local] = false;
+            },
         }
     }
 }