Previously, any file would be read, which is both unnecessary, and causes issues if irrelevant non-Unicode files were read (e.g. `.DS_STORE`).

This commit fixes a hard error where the `#![feature(rust_2018_preview)]`
feature was forbidden to be mentioned when the `--edition 2018` flag was passed.
This instead silently accepts that feature gate despite it not being necessary.
It's intended that this will help ease the transition into the 2018 edition as
users will, for the time being, start off with the `rust_2018_preview` feature
and no longer immediately need to remove it.

Closes rust-lang#50662

Currently the lint for removing `extern crate` suggests removing `extern crate`
most of the time, but the rest of the time it suggest replacing it with `use
crate_name`. Unfortunately though when spliced into the original code you're
replacing

    extern crate foo;

with

    use foo

which is syntactically invalid! This commit ensure that the trailing semicolon
is included in rustc's suggestion to ensure that the code continues to compile
afterwards.

This commit updates one of the edition lints to only suggest deleting `extern
crate` if it actually works. Otherwise this can yield some confusing behavior
with rustfix specifically where if you accidentally deny the `rust_2018_idioms`
lint in the 2015 edition it's suggesting features that don't work!

Generate an IO error if the offset is out of bounds for the system call.

standard binutils on openbsd is too old to do proper job with i128
code.

…veklabnik

fs::write: Add example writing a &str

This adds an example to the documentation for `fs::write` that demonstrates the use of the `AsRef<[u8]>` implementation for &str. Experienced users should already recognize the possibility from the type signature, but new users may not recognize the significance.

…nnytm

Do not silently truncate offsets for `read_at`/`write_at` on emscripten

Generate an IO error if the offset is out of bounds for the system call.

…richton

AppVeyor: Read back trace from crash dump on failure.

This is an attempt to debug spurious access violations on Windows (rust-lang#33434, rust-lang#50604). Thanks to rust-lang#50276, there should be minidumps to read when rustc segfault.

(The implementation is based on <https://github.com/springmeyer/travis-coredump/blob/master/test.bat>.)

…=alexcrichton

Ignore non .rs files for tidy libcoretest

Previously, any file would be read, which is both unnecessary, and causes issues if irrelevant non-Unicode files were read (e.g. `.DS_STORE`).

…nishearth

rustc: Allow an edition's feature on that edition

This commit fixes a hard error where the `#![feature(rust_2018_preview)]`
feature was forbidden to be mentioned when the `--edition 2018` flag was passed.
This instead silently accepts that feature gate despite it not being necessary.
It's intended that this will help ease the transition into the 2018 edition as
users will, for the time being, start off with the `rust_2018_preview` feature
and no longer immediately need to remove it.

Closes rust-lang#50662

…-unless-works, r=Manishearth

rustc: Only suggest deleting `extern crate` if it works

This commit updates one of the edition lints to only suggest deleting `extern
crate` if it actually works. Otherwise this can yield some confusing behavior
with rustfix specifically where if you accidentally deny the `rust_2018_idioms`
lint in the 2015 edition it's suggesting features that don't work!

…rrect-span, r=Manishearth

rustc: Include semicolon when removing `extern crate`

Currently the lint for removing `extern crate` suggests removing `extern crate`
most of the time, but the rest of the time it suggest replacing it with `use
crate_name`. Unfortunately though when spliced into the original code you're
replacing

    extern crate foo;

with

    use foo

which is syntactically invalid! This commit ensure that the trailing semicolon
is included in rustc's suggestion to ensure that the code continues to compile
afterwards.

Update openbsd targets

- add a new target `aarch64-unknown-openbsd`
- update `i686-unknown-openbsd` to use lld with clang, in order to correctly link binaries with `i128`