Auto merge of #53884 - kennytm:rollup, r=kennytm

Rollup of 9 pull requests

Successful merges:

 - #53076 (set cfg(rustdoc) when rustdoc is running on a crate)
 - #53622 (cleanup: Add main functions to some UI tests)
 - #53769 (Also link Clippy repo in the CONTRIBUTING.md file)
 - #53774 (Add rust-gdbgui script.)
 - #53781 (bench: libcore: fix build failure of any.rs benchmark (use "dyn Any"))
 - #53782 (Make Arc cloning mechanics clearer in module docs)
 - #53790 (Add regression test for issue #52060)
 - #53801 (Prevent duplicated impl on foreign types)
 - #53850 (Nuke the `const_to_allocation` query)

Author: bors

Diff for: CONTRIBUTING.md

@@ -405,7 +405,8 @@ before the PR is merged.
 [breaking-tools-built-with-the-compiler]: #breaking-tools-built-with-the-compiler
 
 Rust's build system builds a number of tools that make use of the
-internals of the compiler. This includes clippy,
+internals of the compiler. This includes 
+[Clippy](https://github.com/rust-lang-nursery/rust-clippy),
 [RLS](https://github.com/rust-lang-nursery/rls) and
 [rustfmt](https://github.com/rust-lang-nursery/rustfmt). If these tools
 break because of your changes, you may run into a sort of "chicken and egg"

Diff for: src/bootstrap/bin/rustdoc.rs

@@ -37,6 +37,8 @@ fn main() {
     let mut dylib_path = bootstrap::util::dylib_path();
     dylib_path.insert(0, PathBuf::from(libdir.clone()));
 
+    //FIXME(misdreavus): once stdsimd uses cfg(rustdoc) instead of cfg(dox), remove the `--cfg dox`
+    //arguments here
     let mut cmd = Command::new(rustdoc);
     cmd.args(&args)
         .arg("--cfg")

Diff for: src/doc/rustdoc/src/unstable-features.md

@@ -106,27 +106,25 @@ The `#[doc(cfg(...))]` attribute has another effect: When Rustdoc renders docume
 item, it will be accompanied by a banner explaining that the item is only available on certain
 platforms.
 
-As mentioned earlier, getting the items to Rustdoc requires some extra preparation. The standard
-library adds a `--cfg dox` flag to every Rustdoc command, but the same thing can be accomplished by
-adding a feature to your Cargo.toml and adding `--feature dox` (or whatever you choose to name the
-feature) to your `cargo doc` calls.
+For Rustdoc to document an item, it needs to see it, regardless of what platform it's currently
+running on. To aid this, Rustdoc sets the flag `#[cfg(rustdoc)]` when running on your crate.
+Combining this with the target platform of a given item allows it to appear when building your crate
+normally on that platform, as well as when building documentation anywhere.
 
-Either way, once you create an environment for the documentation, you can start to augment your
-`#[cfg]` attributes to allow both the target platform *and* the documentation configuration to leave
-the item in. For example, `#[cfg(any(windows, feature = "dox"))]` will preserve the item either on
-Windows or during the documentation process. Then, adding a new attribute `#[doc(cfg(windows))]`
-will tell Rustdoc that the item is supposed to be used on Windows. For example:
+For example, `#[cfg(any(windows, rustdoc))]` will preserve the item either on Windows or during the
+documentation process. Then, adding a new attribute `#[doc(cfg(windows))]` will tell Rustdoc that
+the item is supposed to be used on Windows. For example:
 
 ```rust
 #![feature(doc_cfg)]
 
 /// Token struct that can only be used on Windows.
-#[cfg(any(windows, feature = "dox"))]
+#[cfg(any(windows, rustdoc))]
 #[doc(cfg(windows))]
 pub struct WindowsToken;
 
 /// Token struct that can only be used on Unix.
-#[cfg(any(unix, feature = "dox"))]
+#[cfg(any(unix, rustdoc))]
 #[doc(cfg(unix))]
 pub struct UnixToken;
 ```

Diff for: src/doc/unstable-book/src/language-features/doc-cfg.md

@@ -12,13 +12,17 @@ This attribute has two effects:
 
 2. The item's doc-tests will only run on the specific platform.
 
+In addition to allowing the use of the `#[doc(cfg)]` attribute, this feature enables the use of a
+special conditional compilation flag, `#[cfg(rustdoc)]`, set whenever building documentation on your
+crate.
+
 This feature was introduced as part of PR [#43348] to allow the platform-specific parts of the
 standard library be documented.
 
 ```rust
 #![feature(doc_cfg)]
 
-#[cfg(any(windows, feature = "documentation"))]
+#[cfg(any(windows, rustdoc))]
 #[doc(cfg(windows))]
 /// The application's icon in the notification area (a.k.a. system tray).
 ///
@@ -39,4 +43,4 @@ pub struct Icon {
 ```
 
 [#43781]: https://github.com/rust-lang/rust/issues/43781
-[#43348]: https://github.com/rust-lang/rust/issues/43348
+[#43348]: https://github.com/rust-lang/rust/issues/43348

Diff for: src/etc/rust-gdbgui

@@ -0,0 +1,65 @@
+#!/bin/sh
+# Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+# file at the top-level directory of this distribution and at
+# http://rust-lang.org/COPYRIGHT.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+# Exit if anything fails
+set -e
+
+if [ $# -eq 0 ] || [ "$1" = "-h" ] || [ "$1" = "-help" ] || [ "$1" = "--help" ]; then
+    echo "
+rust-gdbgui
+===========
+gdbgui - https://gdbgui.com - is a graphical front-end to GDB
+that runs in a browser. This script invokes gdbgui with the Rust
+pretty printers loaded.
+
+Simple usage  : rust-gdbgui target/debug/myprog
+With arguments: rust-gdbgui 'target/debug/myprog arg1 arg2...'
+  (note the quotes)
+
+
+Hints
+=====
+gdbgui won't be able to find the rust 'main' method automatically, so
+in its options make sure to disable the 'Add breakpoint to main after
+loading executable' setting to avoid a 'File not found: main' warning
+on startup.
+
+Instead, type 'main' into gdbgui's file browser and you should get
+auto-completion on the filename. Just pick 'main.rs', add a breakpoint
+by clicking in the line number gutter, and type 'r' or hit the Restart
+icon to start your program running.
+"
+    exit 0
+fi
+
+# Find out where the pretty printer Python module is
+RUSTC_SYSROOT=`rustc --print=sysroot`
+GDB_PYTHON_MODULE_DIRECTORY="$RUSTC_SYSROOT/lib/rustlib/etc"
+
+# Set the environment variable `RUST_GDB` to overwrite the call to a
+# different/specific command (defaults to `gdb`).
+RUST_GDB="${RUST_GDB:-gdb}"
+
+# Set the environment variable `RUST_GDBGUI` to overwrite the call to a
+# different/specific command (defaults to `gdbgui`).
+RUST_GDBGUI="${RUST_GDBGUI:-gdbgui}"
+
+# These arguments get passed through to GDB and make it load the
+# Rust pretty printers.
+GDB_ARGS="--directory=\"$GDB_PYTHON_MODULE_DIRECTORY\" -iex \"add-auto-load-safe-path $GDB_PYTHON_MODULE_DIRECTORY\""
+
+# Finally we execute gdbgui.
+PYTHONPATH="$PYTHONPATH:$GDB_PYTHON_MODULE_DIRECTORY" \
+  exec ${RUST_GDBGUI} \
+  --gdb ${RUST_GDB} \
+  --gdb-args "${GDB_ARGS}" \
+  "${@}"
+

Diff for: src/liballoc/sync.rs

@@ -49,9 +49,10 @@ const MAX_REFCOUNT: usize = (isize::MAX) as usize;
 ///
 /// The type `Arc<T>` provides shared ownership of a value of type `T`,
 /// allocated in the heap. Invoking [`clone`][clone] on `Arc` produces
-/// a new pointer to the same value in the heap. When the last `Arc`
-/// pointer to a given value is destroyed, the pointed-to value is
-/// also destroyed.
+/// a new `Arc` instance, which points to the same value on the heap as the
+/// source `Arc`, while increasing a reference count. When the last `Arc`
+/// pointer to a given value is destroyed, the pointed-to value is also
+/// destroyed.
 ///
 /// Shared references in Rust disallow mutation by default, and `Arc` is no
 /// exception: you cannot generally obtain a mutable reference to something
@@ -107,7 +108,7 @@ const MAX_REFCOUNT: usize = (isize::MAX) as usize;
 /// // The two syntaxes below are equivalent.
 /// let a = foo.clone();
 /// let b = Arc::clone(&foo);
-/// // a and b both point to the same memory location as foo.
+/// // a, b, and foo are all Arcs that point to the same memory location
 /// ```
 ///
 /// The [`Arc::clone(&from)`] syntax is the most idiomatic because it conveys more explicitly

Diff for: src/libcore/benches/any.rs

@@ -15,7 +15,7 @@ use test::{Bencher, black_box};
 fn bench_downcast_ref(b: &mut Bencher) {
     b.iter(|| {
         let mut x = 0;
-        let mut y = &mut x as &mut Any;
+        let mut y = &mut x as &mut dyn Any;
         black_box(&mut y);
         black_box(y.downcast_ref::<isize>() == Some(&0));
     });

Diff for: src/libcore/macros.rs

@@ -541,7 +541,7 @@ macro_rules! unimplemented {
 /// into libsyntax itself.
 ///
 /// For more information, see documentation for `std`'s macros.
-#[cfg(dox)]
+#[cfg(rustdoc)]
 mod builtin {
 
     /// Unconditionally causes compilation to fail with the given error message when encountered.

Diff for: src/librustc/dep_graph/dep_node.rs

@@ -75,7 +75,7 @@ use traits::query::{
     CanonicalPredicateGoal, CanonicalTypeOpProvePredicateGoal, CanonicalTypeOpNormalizeGoal,
 };
 use ty::{TyCtxt, FnSig, Instance, InstanceDef,
-         ParamEnv, ParamEnvAnd, Predicate, PolyFnSig, PolyTraitRef, Ty, self};
+         ParamEnv, ParamEnvAnd, Predicate, PolyFnSig, PolyTraitRef, Ty};
 use ty::subst::Substs;
 
 // erase!() just makes tokens go away. It's used to specify which macro argument
@@ -632,7 +632,6 @@ define_dep_nodes!( <'tcx>
     // queries). Making them anonymous avoids hashing the result, which
     // may save a bit of time.
     [anon] EraseRegionsTy { ty: Ty<'tcx> },
-    [anon] ConstToAllocation { val: &'tcx ty::Const<'tcx> },
 
     [input] Freevars(DefId),
     [input] MaybeUnusedTraitImport(DefId),

Diff for: src/librustc/ty/query/config.rs

@@ -198,12 +198,6 @@ impl<'tcx> QueryDescription<'tcx> for queries::super_predicates_of<'tcx> {
     }
 }
 
-impl<'tcx> QueryDescription<'tcx> for queries::const_to_allocation<'tcx> {
-    fn describe(_tcx: TyCtxt, val: &'tcx ty::Const<'tcx>) -> String {
-        format!("converting constant `{:?}` to an allocation", val)
-    }
-}
-
 impl<'tcx> QueryDescription<'tcx> for queries::erase_regions_ty<'tcx> {
     fn describe(_tcx: TyCtxt, ty: Ty<'tcx>) -> String {
         format!("erasing regions from `{:?}`", ty)

Diff for: src/librustc/ty/query/mod.rs

@@ -30,7 +30,7 @@ use middle::exported_symbols::{SymbolExportLevel, ExportedSymbol};
 use mir::interpret::ConstEvalResult;
 use mir::mono::{CodegenUnit, Stats};
 use mir;
-use mir::interpret::{GlobalId, Allocation};
+use mir::interpret::GlobalId;
 use session::{CompileResult, CrateDisambiguator};
 use session::config::OutputFilenames;
 use traits::{self, Vtable};
@@ -286,11 +286,6 @@ define_queries! { <'tcx>
         /// other items (such as enum variant explicit discriminants).
         [] fn const_eval: const_eval_dep_node(ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>)
             -> ConstEvalResult<'tcx>,
-
-        /// Converts a constant value to a constant allocation
-        [] fn const_to_allocation: const_to_allocation(
-            &'tcx ty::Const<'tcx>
-        ) -> &'tcx Allocation,
     },
 
     TypeChecking {
@@ -706,12 +701,6 @@ fn erase_regions_ty<'tcx>(ty: Ty<'tcx>) -> DepConstructor<'tcx> {
     DepConstructor::EraseRegionsTy { ty }
 }
 
-fn const_to_allocation<'tcx>(
-    val: &'tcx ty::Const<'tcx>,
-) -> DepConstructor<'tcx> {
-    DepConstructor::ConstToAllocation { val }
-}
-
 fn type_param_predicates<'tcx>((item_id, param_id): (DefId, DefId)) -> DepConstructor<'tcx> {
     DepConstructor::TypeParamPredicates {
         item_id,

Diff for: src/librustc/ty/query/plumbing.rs

@@ -1062,7 +1062,6 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         DepKind::FulfillObligation |
         DepKind::VtableMethods |
         DepKind::EraseRegionsTy |
-        DepKind::ConstToAllocation |
         DepKind::NormalizeProjectionTy |
         DepKind::NormalizeTyAfterErasingRegions |
         DepKind::ImpliedOutlivesBounds |

Diff for: src/librustc_mir/interpret/memory.rs

@@ -22,7 +22,7 @@ use std::ptr;
 
 use rustc::ty::{self, Instance, query::TyCtxtAt};
 use rustc::ty::layout::{self, Align, TargetDataLayout, Size, HasDataLayout};
-use rustc::mir::interpret::{Pointer, AllocId, Allocation, ScalarMaybeUndef, GlobalId,
+use rustc::mir::interpret::{Pointer, AllocId, Allocation, ConstValue, ScalarMaybeUndef, GlobalId,
                             EvalResult, Scalar, EvalErrorKind, AllocType, PointerArithmetic,
                             truncate};
 pub use rustc::mir::interpret::{write_target_uint, read_target_uint};
@@ -340,9 +340,12 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
             // no need to report anything, the const_eval call takes care of that for statics
             assert!(tcx.is_static(def_id).is_some());
             EvalErrorKind::ReferencedConstant(err).into()
-        }).map(|val| {
-            // FIXME We got our static (will be a ByRef), now we make a *copy*?!?
-            tcx.const_to_allocation(val)
+        }).map(|const_val| {
+            if let ConstValue::ByRef(_, allocation, _) = const_val.val {
+                allocation
+            } else {
+                bug!("Matching on non-ByRef static")
+            }
         })
     }
 

Diff for: src/librustc_mir/lib.rs

@@ -92,7 +92,6 @@ pub fn provide(providers: &mut Providers) {
     shim::provide(providers);
     transform::provide(providers);
     providers.const_eval = interpret::const_eval_provider;
-    providers.const_to_allocation = interpret::const_to_allocation_provider;
     providers.check_match = hair::pattern::check_match;
 }
 

Diff for: src/librustc_typeck/check/mod.rs

@@ -94,7 +94,7 @@ use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin};
 use rustc::infer::anon_types::AnonTypeDecl;
 use rustc::infer::type_variable::{TypeVariableOrigin};
 use rustc::middle::region;
-use rustc::mir::interpret::{GlobalId};
+use rustc::mir::interpret::{ConstValue, GlobalId};
 use rustc::ty::subst::{CanonicalSubsts, UnpackedKind, Subst, Substs};
 use rustc::traits::{self, ObligationCause, ObligationCauseCode, TraitEngine};
 use rustc::ty::{self, Ty, TyCtxt, GenericParamDefKind, Visibility, ToPredicate, RegionKind};
@@ -1375,7 +1375,11 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt, id: DefId, span: Span) {
     };
     let param_env = ty::ParamEnv::reveal_all();
     if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
-        let alloc = tcx.const_to_allocation(static_);
+        let alloc = if let ConstValue::ByRef(_, allocation, _) = static_.val {
+            allocation
+        } else {
+            bug!("Matching on non-ByRef static")
+        };
         if alloc.relocations.len() != 0 {
             let msg = "statics with a custom `#[link_section]` must be a \
                        simple list of bytes on the wasm target with no \

Diff for: src/librustdoc/html/render.rs

@@ -2956,12 +2956,16 @@ fn item_trait(
                 </h2>
             ")?;
 
+            let mut foreign_cache = FxHashSet();
             for implementor in foreign {
-                let assoc_link = AssocItemLink::GotoSource(
-                    implementor.impl_item.def_id, &implementor.inner_impl().provided_trait_methods
-                );
-                render_impl(w, cx, &implementor, assoc_link,
-                            RenderMode::Normal, implementor.impl_item.stable_since(), false)?;
+                if foreign_cache.insert(implementor.inner_impl().to_string()) {
+                    let assoc_link = AssocItemLink::GotoSource(
+                        implementor.impl_item.def_id,
+                        &implementor.inner_impl().provided_trait_methods
+                    );
+                    render_impl(w, cx, &implementor, assoc_link,
+                                RenderMode::Normal, implementor.impl_item.stable_since(), false)?;
+                }
             }
         }
 

Diff for: src/librustdoc/lib.rs

@@ -477,7 +477,8 @@ fn main_args(args: &[String]) -> isize {
 
     let output = matches.opt_str("o").map(|s| PathBuf::from(&s));
     let css_file_extension = matches.opt_str("e").map(|s| PathBuf::from(&s));
-    let cfgs = matches.opt_strs("cfg");
+    let mut cfgs = matches.opt_strs("cfg");
+    cfgs.push("rustdoc".to_string());
 
     if let Some(ref p) = css_file_extension {
         if !p.is_file() {
@@ -671,7 +672,8 @@ where R: 'static + Send,
     for s in &matches.opt_strs("L") {
         paths.add_path(s, ErrorOutputType::default());
     }
-    let cfgs = matches.opt_strs("cfg");
+    let mut cfgs = matches.opt_strs("cfg");
+    cfgs.push("rustdoc".to_string());
     let triple = matches.opt_str("target").map(|target| {
         if target.ends_with(".json") {
             TargetTriple::TargetPath(PathBuf::from(target))

Diff for: src/libstd/macros.rs

@@ -309,7 +309,7 @@ macro_rules! assert_approx_eq {
 /// These macros do not have any corresponding definition with a `macro_rules!`
 /// macro, but are documented here. Their implementations can be found hardcoded
 /// into libsyntax itself.
-#[cfg(dox)]
+#[cfg(rustdoc)]
 mod builtin {
 
     /// Unconditionally causes compilation to fail with the given error message when encountered.

Diff for: src/libstd/os/mod.rs

@@ -14,7 +14,7 @@
 #![allow(missing_docs, nonstandard_style, missing_debug_implementations)]
 
 cfg_if! {
-    if #[cfg(dox)] {
+    if #[cfg(rustdoc)] {
 
         // When documenting libstd we want to show unix/windows/linux modules as
         // these are the "main modules" that are used across platforms. This

Diff for: src/libstd/sys/mod.rs

@@ -57,7 +57,7 @@ cfg_if! {
 // then later used in the `std::os` module when documenting, for example,
 // Windows when we're compiling for Linux.
 
-#[cfg(dox)]
+#[cfg(rustdoc)]
 cfg_if! {
     if #[cfg(any(unix, target_os = "redox"))] {
         // On unix we'll document what's already available
@@ -77,7 +77,7 @@ cfg_if! {
     }
 }
 
-#[cfg(dox)]
+#[cfg(rustdoc)]
 cfg_if! {
     if #[cfg(windows)] {
         // On windows we'll just be documenting what's already available