Auto merge of rust-lang#70275 - Dylan-DPC:rollup-1fbosob, r=Dylan-DPC

Rollup of 10 pull requests

Successful merges:

 - rust-lang#68099 (Amend Rc/Arc::from_raw() docs regarding unsafety)
 - rust-lang#70172 (parse/lexer: support `StringReader::retokenize` called on external files.)
 - rust-lang#70209 (parser: recover on `for<'a> |...| body` closures)
 - rust-lang#70223 (fix type of const params in associated types.)
 - rust-lang#70229 (more clippy fixes)
 - rust-lang#70240 (Return NonZeroU64 from ThreadId::as_u64.)
 - rust-lang#70250 (Remove wrong entry from RELEASES.md)
 - rust-lang#70253 (Remove another wrong entry from RELEASES.md)
 - rust-lang#70254 (couple more clippy fixes (let_and_return, if_same_then_else))
 - rust-lang#70266 (proc_macro_harness: Use item header spans for errors)

Failed merges:

r? @ghost

Author: bors

RELEASES.md

@@ -4838,7 +4838,6 @@ Version 1.11.0 (2016-08-18)
 Language
 --------
 
-* [`cfg_attr` works on `path` attributes](https://github.com/rust-lang/rust/pull/34546)
 * [Support nested `cfg_attr` attributes](https://github.com/rust-lang/rust/pull/34216)
 * [Allow statement-generating braced macro invocations at the end of blocks](https://github.com/rust-lang/rust/pull/34436)
 * [Macros can be expanded inside of trait definitions](https://github.com/rust-lang/rust/pull/34213)
@@ -4957,8 +4956,6 @@ Version 1.10.0 (2016-07-07)
 Language
 --------
 
-* [Allow `concat_idents!` in type positions as well as in expression
-  positions](https://github.com/rust-lang/rust/pull/33735).
 * [`Copy` types are required to have a trivial implementation of `Clone`](https://github.com/rust-lang/rust/pull/33420).
   [RFC 1521](https://github.com/rust-lang/rfcs/blob/master/text/1521-copy-clone-semantics.md).
 * [Single-variant enums support the `#[repr(..)]` attribute](https://github.com/rust-lang/rust/pull/33355).

src/liballoc/rc.rs

@@ -259,6 +259,10 @@ use crate::vec::Vec;
 #[cfg(test)]
 mod tests;
 
+// This is repr(C) to future-proof against possible field-reordering, which
+// would interfere with otherwise safe [into|from]_raw() of transmutable
+// inner types.
+#[repr(C)]
 struct RcBox<T: ?Sized> {
     strong: Cell<usize>,
     weak: Cell<usize>,
@@ -580,15 +584,24 @@ impl<T: ?Sized> Rc<T> {
         }
     }
 
-    /// Constructs an `Rc` from a raw pointer.
+    /// Constructs an `Rc<T>` from a raw pointer.
     ///
-    /// The raw pointer must have been previously returned by a call to a
-    /// [`Rc::into_raw`][into_raw].
+    /// The raw pointer must have been previously returned by a call to
+    /// [`Rc<U>::into_raw`][into_raw] where `U` must have the same size
+    /// and alignment as `T`. This is trivially true if `U` is `T`.
+    /// Note that if `U` is not `T` but has the same size and alignment, this is
+    /// basically like transmuting references of different types. See
+    /// [`mem::transmute`][transmute] for more information on what
+    /// restrictions apply in this case.
     ///
-    /// This function is unsafe because improper use may lead to memory problems. For example, a
-    /// double-free may occur if the function is called twice on the same raw pointer.
+    /// The user of `from_raw` has to make sure a specific value of `T` is only
+    /// dropped once.
+    ///
+    /// This function is unsafe because improper use may lead to memory unsafety,
+    /// even if the returned `Rc<T>` is never accessed.
     ///
     /// [into_raw]: struct.Rc.html#method.into_raw
+    /// [transmute]: ../../std/mem/fn.transmute.html
     ///
     /// # Examples
     ///

src/liballoc/slice.rs

@@ -145,8 +145,7 @@ mod hack {
         unsafe {
             let len = b.len();
             let b = Box::into_raw(b);
-            let xs = Vec::from_raw_parts(b as *mut T, len, len);
-            xs
+            Vec::from_raw_parts(b as *mut T, len, len)
         }
     }
 

src/liballoc/sync.rs

@@ -287,6 +287,10 @@ impl<T: ?Sized + fmt::Debug> fmt::Debug for Weak<T> {
     }
 }
 
+// This is repr(C) to future-proof against possible field-reordering, which
+// would interfere with otherwise safe [into|from]_raw() of transmutable
+// inner types.
+#[repr(C)]
 struct ArcInner<T: ?Sized> {
     strong: atomic::AtomicUsize,
 
@@ -577,15 +581,24 @@ impl<T: ?Sized> Arc<T> {
         }
     }
 
-    /// Constructs an `Arc` from a raw pointer.
+    /// Constructs an `Arc<T>` from a raw pointer.
     ///
-    /// The raw pointer must have been previously returned by a call to a
-    /// [`Arc::into_raw`][into_raw].
+    /// The raw pointer must have been previously returned by a call to
+    /// [`Arc<U>::into_raw`][into_raw] where `U` must have the same size and
+    /// alignment as `T`. This is trivially true if `U` is `T`.
+    /// Note that if `U` is not `T` but has the same size and alignment, this is
+    /// basically like transmuting references of different types. See
+    /// [`mem::transmute`][transmute] for more information on what
+    /// restrictions apply in this case.
     ///
-    /// This function is unsafe because improper use may lead to memory problems. For example, a
-    /// double-free may occur if the function is called twice on the same raw pointer.
+    /// The user of `from_raw` has to make sure a specific value of `T` is only
+    /// dropped once.
+    ///
+    /// This function is unsafe because improper use may lead to memory unsafety,
+    /// even if the returned `Arc<T>` is never accessed.
     ///
     /// [into_raw]: struct.Arc.html#method.into_raw
+    /// [transmute]: ../../std/mem/fn.transmute.html
     ///
     /// # Examples
     ///

src/librustc/hir/map/mod.rs

@@ -1044,9 +1044,7 @@ pub(super) fn index_hir<'tcx>(tcx: TyCtxt<'tcx>, cnum: CrateNum) -> &'tcx Indexe
         collector.finalize_and_compute_crate_hash(crate_disambiguator, &*tcx.cstore, cmdline_args)
     };
 
-    let map = tcx.arena.alloc(IndexedHir { crate_hash, map });
-
-    map
+    tcx.arena.alloc(IndexedHir { crate_hash, map })
 }
 
 /// Identical to the `PpAnn` implementation for `hir::Crate`,

src/librustc/ty/layout.rs

@@ -381,12 +381,8 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         // Field 5 would be the first element, so memory_index is i:
         // Note: if we didn't optimize, it's already right.
 
-        let memory_index;
-        if optimize {
-            memory_index = invert_mapping(&inverse_memory_index);
-        } else {
-            memory_index = inverse_memory_index;
-        }
+        let memory_index =
+            if optimize { invert_mapping(&inverse_memory_index) } else { inverse_memory_index };
 
         let size = min_size.align_to(align.abi);
         let mut abi = Abi::Aggregate { sized };
@@ -944,33 +940,33 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                             let offset = st[i].fields.offset(field_index) + niche.offset;
                             let size = st[i].size;
 
-                            let mut abi = match st[i].abi {
-                                Abi::Scalar(_) => Abi::Scalar(niche_scalar.clone()),
-                                Abi::ScalarPair(ref first, ref second) => {
-                                    // We need to use scalar_unit to reset the
-                                    // valid range to the maximal one for that
-                                    // primitive, because only the niche is
-                                    // guaranteed to be initialised, not the
-                                    // other primitive.
-                                    if offset.bytes() == 0 {
-                                        Abi::ScalarPair(
-                                            niche_scalar.clone(),
-                                            scalar_unit(second.value),
-                                        )
-                                    } else {
-                                        Abi::ScalarPair(
-                                            scalar_unit(first.value),
-                                            niche_scalar.clone(),
-                                        )
+                            let abi = if st.iter().all(|v| v.abi.is_uninhabited()) {
+                                Abi::Uninhabited
+                            } else {
+                                match st[i].abi {
+                                    Abi::Scalar(_) => Abi::Scalar(niche_scalar.clone()),
+                                    Abi::ScalarPair(ref first, ref second) => {
+                                        // We need to use scalar_unit to reset the
+                                        // valid range to the maximal one for that
+                                        // primitive, because only the niche is
+                                        // guaranteed to be initialised, not the
+                                        // other primitive.
+                                        if offset.bytes() == 0 {
+                                            Abi::ScalarPair(
+                                                niche_scalar.clone(),
+                                                scalar_unit(second.value),
+                                            )
+                                        } else {
+                                            Abi::ScalarPair(
+                                                scalar_unit(first.value),
+                                                niche_scalar.clone(),
+                                            )
+                                        }
                                     }
+                                    _ => Abi::Aggregate { sized: true },
                                 }
-                                _ => Abi::Aggregate { sized: true },
                             };
 
-                            if st.iter().all(|v| v.abi.is_uninhabited()) {
-                                abi = Abi::Uninhabited;
-                            }
-
                             let largest_niche =
                                 Niche::from_scalar(dl, offset, niche_scalar.clone());
 

src/librustc/ty/query/plumbing.rs

@@ -746,7 +746,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// side-effects -- e.g., in order to report errors for erroneous programs.
     ///
     /// Note: The optimization is only available during incr. comp.
-    pub(super) fn ensure_query<Q: QueryDescription<'tcx> + 'tcx>(self, key: Q::Key) -> () {
+    pub(super) fn ensure_query<Q: QueryDescription<'tcx> + 'tcx>(self, key: Q::Key) {
         if Q::EVAL_ALWAYS {
             let _ = self.get_query::<Q>(DUMMY_SP, key);
             return;

src/librustc_builtin_macros/deriving/generic/mod.rs

@@ -1056,8 +1056,9 @@ impl<'a> MethodDef<'a> {
                     self_: field,
                     other: other_fields
                         .iter_mut()
-                        .map(|l| match l.next().unwrap() {
-                            (.., ex, _) => ex,
+                        .map(|l| {
+                            let (.., ex, _) = l.next().unwrap();
+                            ex
                         })
                         .collect(),
                     attrs,

src/librustc_builtin_macros/proc_macro_harness.rs

@@ -10,6 +10,7 @@ use rustc_expand::base::{ExtCtxt, Resolver};
 use rustc_expand::expand::{AstFragment, ExpansionConfig};
 use rustc_session::parse::ParseSess;
 use rustc_span::hygiene::AstPass;
+use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{kw, sym};
 use rustc_span::{Span, DUMMY_SP};
 use smallvec::smallvec;
@@ -44,6 +45,7 @@ struct CollectProcMacros<'a> {
     macros: Vec<ProcMacro>,
     in_root: bool,
     handler: &'a rustc_errors::Handler,
+    source_map: &'a SourceMap,
     is_proc_macro_crate: bool,
     is_test_crate: bool,
 }
@@ -65,6 +67,7 @@ pub fn inject(
         macros: Vec::new(),
         in_root: true,
         handler,
+        source_map: sess.source_map(),
         is_proc_macro_crate,
         is_test_crate,
     };
@@ -195,7 +198,7 @@ impl<'a> CollectProcMacros<'a> {
             } else {
                 "functions tagged with `#[proc_macro_derive]` must be `pub`"
             };
-            self.handler.span_err(item.span, msg);
+            self.handler.span_err(self.source_map.def_span(item.span), msg);
         }
     }
 
@@ -214,7 +217,7 @@ impl<'a> CollectProcMacros<'a> {
             } else {
                 "functions tagged with `#[proc_macro_attribute]` must be `pub`"
             };
-            self.handler.span_err(item.span, msg);
+            self.handler.span_err(self.source_map.def_span(item.span), msg);
         }
     }
 
@@ -233,7 +236,7 @@ impl<'a> CollectProcMacros<'a> {
             } else {
                 "functions tagged with `#[proc_macro]` must be `pub`"
             };
-            self.handler.span_err(item.span, msg);
+            self.handler.span_err(self.source_map.def_span(item.span), msg);
         }
     }
 }
@@ -244,7 +247,7 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
             if self.is_proc_macro_crate && attr::contains_name(&item.attrs, sym::macro_export) {
                 let msg =
                     "cannot export macro_rules! macros from a `proc-macro` crate type currently";
-                self.handler.span_err(item.span, msg);
+                self.handler.span_err(self.source_map.def_span(item.span), msg);
             }
         }
 
@@ -295,7 +298,7 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
 
         let attr = match found_attr {
             None => {
-                self.check_not_pub_in_root(&item.vis, item.span);
+                self.check_not_pub_in_root(&item.vis, self.source_map.def_span(item.span));
                 let prev_in_root = mem::replace(&mut self.in_root, false);
                 visit::walk_item(self, item);
                 self.in_root = prev_in_root;

src/librustc_codegen_ssa/back/rpath.rs

@@ -81,9 +81,7 @@ fn get_rpaths(config: &mut RPathConfig<'_>, libs: &[PathBuf]) -> Vec<String> {
     rpaths.extend_from_slice(&fallback_rpaths);
 
     // Remove duplicates
-    let rpaths = minimize_rpaths(&rpaths);
-
-    rpaths
+    minimize_rpaths(&rpaths)
 }
 
 fn get_rpaths_relative_to_output(config: &mut RPathConfig<'_>, libs: &[PathBuf]) -> Vec<String> {