Rollup of 13 pull requests

.github/workflows/ci.yml

@@ -431,15 +431,15 @@ jobs:
           - name: x86_64-mingw-1
             env:
               SCRIPT: make ci-mingw-subset-1
-              RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-gnu"
+              RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-gnu --enable-profiler"
               CUSTOM_MINGW: 1
               NO_DEBUG_ASSERTIONS: 1
               NO_LLVM_ASSERTIONS: 1
             os: windows-latest-xl
           - name: x86_64-mingw-2
             env:
               SCRIPT: make ci-mingw-subset-2
-              RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-gnu"
+              RUST_CONFIGURE_ARGS: "--build=x86_64-pc-windows-gnu --enable-profiler"
               CUSTOM_MINGW: 1
             os: windows-latest-xl
           - name: dist-x86_64-msvc

Cargo.lock

@@ -3720,7 +3720,6 @@ name = "rustc_middle"
 version = "0.0.0"
 dependencies = [
  "bitflags",
- "byteorder",
  "chalk-ir",
  "measureme",
  "polonius-engine",

README.md

@@ -243,6 +243,8 @@ The Rust community congregates in a few places:
 If you are interested in contributing to the Rust project, please take a look
 at the [Getting Started][gettingstarted] guide in the [rustc-dev-guide].
 
+[rustc-dev-guide]: https://rustc-dev-guide.rust-lang.org
+
 ## License
 
 Rust is primarily distributed under the terms of both the MIT license

compiler/rustc_middle/Cargo.toml

@@ -26,7 +26,6 @@ rustc_index = { path = "../rustc_index" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_span = { path = "../rustc_span" }
-byteorder = { version = "1.3" }
 chalk-ir = "0.14.0"
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }
 measureme = "0.7.1"

compiler/rustc_middle/src/mir/interpret/allocation.rs

@@ -345,10 +345,8 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
 
     /// Reads a *non-ZST* scalar.
     ///
-    /// ZSTs can't be read for two reasons:
-    /// * byte-order cannot work with zero-element buffers;
-    /// * in order to obtain a `Pointer`, we need to check for ZSTness anyway due to integer
-    ///   pointers being valid for ZSTs.
+    /// ZSTs can't be read because in order to obtain a `Pointer`, we need to check
+    /// for ZSTness anyway due to integer pointers being valid for ZSTs.
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
     /// Most likely, you want to call `InterpCx::read_scalar` instead of this method.
@@ -397,10 +395,8 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
 
     /// Writes a *non-ZST* scalar.
     ///
-    /// ZSTs can't be read for two reasons:
-    /// * byte-order cannot work with zero-element buffers;
-    /// * in order to obtain a `Pointer`, we need to check for ZSTness anyway due to integer
-    ///   pointers being valid for ZSTs.
+    /// ZSTs can't be read because in order to obtain a `Pointer`, we need to check
+    /// for ZSTness anyway due to integer pointers being valid for ZSTs.
     ///
     /// It is the caller's responsibility to check bounds and alignment beforehand.
     /// Most likely, you want to call `InterpCx::write_scalar` instead of this method.

compiler/rustc_middle/src/mir/interpret/mod.rs

@@ -98,10 +98,10 @@ mod value;
 use std::convert::TryFrom;
 use std::fmt;
 use std::io;
+use std::io::{Read, Write};
 use std::num::NonZeroU32;
 use std::sync::atomic::{AtomicU32, Ordering};
 
-use byteorder::{BigEndian, LittleEndian, ReadBytesExt, WriteBytesExt};
 use rustc_ast::LitKind;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{HashMapExt, Lock};
@@ -561,19 +561,33 @@ pub fn write_target_uint(
     mut target: &mut [u8],
     data: u128,
 ) -> Result<(), io::Error> {
-    let len = target.len();
+    // This u128 holds an "any-size uint" (since smaller uints can fits in it)
+    // So we do not write all bytes of the u128, just the "payload".
     match endianness {
-        Endian::Little => target.write_uint128::<LittleEndian>(data, len),
-        Endian::Big => target.write_uint128::<BigEndian>(data, len),
-    }
+        Endian::Little => target.write(&data.to_le_bytes())?,
+        Endian::Big => target.write(&data.to_be_bytes()[16 - target.len()..])?,
+    };
+    debug_assert!(target.len() == 0); // We should have filled the target buffer.
+    Ok(())
 }
 
 #[inline]
 pub fn read_target_uint(endianness: Endian, mut source: &[u8]) -> Result<u128, io::Error> {
-    match endianness {
-        Endian::Little => source.read_uint128::<LittleEndian>(source.len()),
-        Endian::Big => source.read_uint128::<BigEndian>(source.len()),
-    }
+    // This u128 holds an "any-size uint" (since smaller uints can fits in it)
+    let mut buf = [0u8; std::mem::size_of::<u128>()];
+    // So we do not read exactly 16 bytes into the u128, just the "payload".
+    let uint = match endianness {
+        Endian::Little => {
+            source.read(&mut buf)?;
+            Ok(u128::from_le_bytes(buf))
+        }
+        Endian::Big => {
+            source.read(&mut buf[16 - source.len()..])?;
+            Ok(u128::from_be_bytes(buf))
+        }
+    };
+    debug_assert!(source.len() == 0); // We should have consumed the source buffer.
+    uint
 }
 
 ////////////////////////////////////////////////////////////////////////////////

compiler/rustc_passes/src/check_attr.rs

@@ -250,13 +250,23 @@ impl CheckAttrVisitor<'tcx> {
                                     None
                                 }
                             }
+                            Target::AssocConst => {
+                                let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
+                                let containing_item = self.tcx.hir().expect_item(parent_hir_id);
+                                // We can't link to trait impl's consts.
+                                let err = "associated constant in trait implementation block";
+                                match containing_item.kind {
+                                    ItemKind::Impl { of_trait: Some(_), .. } => Some(err),
+                                    _ => None,
+                                }
+                            }
                             _ => None,
                         } {
                             self.tcx
                                 .sess
                                 .struct_span_err(
                                     meta.span(),
-                                    &format!("`#[doc(alias = \"...\")]` isn't allowed on {}", err,),
+                                    &format!("`#[doc(alias = \"...\")]` isn't allowed on {}", err),
                                 )
                                 .emit();
                         }

compiler/rustc_typeck/src/check/place_op.rs

@@ -193,7 +193,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// Convert auto-derefs, indices, etc of an expression from `Deref` and `Index`
     /// into `DerefMut` and `IndexMut` respectively.
     ///
-    /// This is a second pass of typechecking derefs/indices. We need this we do not
+    /// This is a second pass of typechecking derefs/indices. We need this because we do not
     /// always know whether a place needs to be mutable or not in the first pass.
     /// This happens whether there is an implicit mutable reborrow, e.g. when the type
     /// is used as the receiver of a method call.
@@ -211,13 +211,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         debug!("convert_place_derefs_to_mutable: exprs={:?}", exprs);
 
         // Fix up autoderefs and derefs.
+        let mut inside_union = false;
         for (i, &expr) in exprs.iter().rev().enumerate() {
             debug!("convert_place_derefs_to_mutable: i={} expr={:?}", i, expr);
 
+            let mut source = self.node_ty(expr.hir_id);
+            if matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::UnDeref, _)) {
+                // Clear previous flag; after a pointer indirection it does not apply any more.
+                inside_union = false;
+            }
+            if source.ty_adt_def().map_or(false, |adt| adt.is_union()) {
+                inside_union = true;
+            }
             // Fix up the autoderefs. Autorefs can only occur immediately preceding
             // overloaded place ops, and will be fixed by them in order to get
             // the correct region.
-            let mut source = self.node_ty(expr.hir_id);
             // Do not mutate adjustments in place, but rather take them,
             // and replace them after mutating them, to avoid having the
             // typeck results borrowed during (`deref_mut`) method resolution.
@@ -236,6 +244,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             if let ty::Ref(region, _, mutbl) = *method.sig.output().kind() {
                                 *deref = OverloadedDeref { region, mutbl };
                             }
+                            // If this is a union field, also throw an error for `DerefMut` of `ManuallyDrop` (see RFC 2514).
+                            // This helps avoid accidental drops.
+                            if inside_union
+                                && source.ty_adt_def().map_or(false, |adt| adt.is_manually_drop())
+                            {
+                                let mut err = self.tcx.sess.struct_span_err(
+                                    expr.span,
+                                    "not automatically applying `DerefMut` on `ManuallyDrop` union field",
+                                );
+                                err.help(
+                                    "writing to this reference calls the destructor for the old value",
+                                );
+                                err.help("add an explicit `*` if that is desired, or call `ptr::write` to not run the destructor");
+                                err.emit();
+                            }
                         }
                     }
                     source = adjustment.target;