Merge ref '1553adfe6884' from rust-lang/rust

Pull recent changes from https://github.com/rust-lang/rust via Josh.

Upstream ref: 1553adfe6884a8f6c28f5a673d3e605535ee0113
Filtered ref: e5ee70aa5f36dacdc6df9490e867c45aa4e51c18

This merge was created using https://github.com/rust-lang/josh-sync.

Author: The Miri Cronjob Bot

src/building/optimized-build.md

@@ -118,7 +118,7 @@ Here is an example of how can `opt-dist` be used locally (outside of CI):
     ```
 3. Run the tool with the `local` mode and provide necessary parameters:
     ```bash
-    ./build/host/stage0-tools-bin/opt-dist local \
+    ./build/host/stage1-tools-bin/opt-dist local \
       --target-triple <target> \ # select target, e.g. "x86_64-unknown-linux-gnu"
       --checkout-dir <path>    \ # path to rust checkout, e.g. "."
       --llvm-dir <path>        \ # path to built LLVM toolchain, e.g. "/foo/bar/llvm/install"

src/stability.md

@@ -182,6 +182,11 @@ of the standard library raises it to a warning with
 `#![warn(deprecated_in_future)]`.
 
 ## unstable_feature_bound
-The `#[unstable_feature_bound(foo)]` attribute can be used together with `#[unstable]` attribute to mark an `impl` of stable type and stable trait as unstable. In std/core, an item annotated with `#[unstable_feature_bound(foo)]` can only be used by another item that is also annotated with `#[unstable_feature_bound(foo)]`. Outside of std/core, using an item with `#[unstable_feature_bound(foo)]` requires the feature to be enabled with `#![feature(foo)]` attribute on the crate. Currently, only `impl`s and free functions can be annotated with `#[unstable_feature_bound]`.
+The `#[unstable_feature_bound(foo)]` attribute can be used together with `#[unstable]` attribute to mark an `impl` of stable type and stable trait as unstable. In std/core, an item annotated with `#[unstable_feature_bound(foo)]` can only be used by another item that is also annotated with `#[unstable_feature_bound(foo)]`. Outside of std/core, using an item with `#[unstable_feature_bound(foo)]` requires the feature to be enabled with `#![feature(foo)]` attribute on the crate.
+
+Currently, the items that can be annotated with `#[unstable_feature_bound]` are:
+- `impl`
+- free function
+- trait
 
 [blog]: https://www.ralfj.de/blog/2018/07/19/const.html