This removes the last dependency on syn 0.12

This removes skeptic from the dependency tree which in turn removes
quite a few other dependencies

added rustc_const_unstable attribute

extended tests

added conversion test

fixed tidy test

added feature attribute

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

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

Cleanup some dependencies

Made some functions in time module const

They may be const, or i missed something?

use fmt::Result where applicable

This is a quite boring PR, but I think the type alias improves readability, so why not use it?

…ster

Remove all reference to DepGraph::work_products

This is an attempt at fixing rust-lang#50500. It will remove the `work_products` key from `DepGraphData` completely, in favour of just passing the relevant data around. I went in a little blindly; everything appears to work just fine but I'd appreciate any additional advice people.

I didn't want to remove too much of what was already there, so I kept the structure pretty much the same (aside from some naming tweaks) - if anyone has suggestions on how to streamline it a little better, happy to follow up.

r? @michaelwoerister

Don't require clippy/miri for beta

r? @kennytm

cc @alexcrichton

I'm trying this out locally atm to see if it works as I think it should. Not sure how to test it for real except wait for the next beta.

fixes rust-lang#50557

…cs, r=cramertj

Update canonicalize docs

I was recently working with file-paths in Rust, and I felt let down by the `std::fs::canonicalize` docs, so I figured I should submit a PR with some suggestions.

I was looking for a method to turn a relative path into an absolute path. The `canonicalize` docs didn't mention the words "relative" or "absolute", but they did mention resolving symlinks (which is a kind of canonicalisation and does not imply converting to absolute), so I assumed that's all it did. To remedy this, I've added the word "absolute" to the description of both `std::fs::canonicalize` and `std::path::Path::canonicalize`.

After calling `canonicalize` on Windows, I ran into a bunch of other problems I would not have expected from the function's behaviour on Linux. Specifically, if you call `canonicalize` on a path:

  - it's allowed to be much longer than it otherwise would
  - `.join("a/slash/delimited/path")` gives you a broken path that Windows can't use, where the same operation would have worked perfectly without `canonicalize` (if the path were short enough)
  - the resulting path may confuse other Windows programs if you pass it to them on the command-line, or write it to a config file that they read, etc.

...so I tried to summarize those behaviours too.

If I understand correctly, those behaviours are a side-effect of calling `GetFinalPathNameByHandle`, and the documentation says `canonicalize` might not call that function in future, so maybe those side-effects shouldn't be part of the function's documentation. However, I bet there's a lot of applications deliberately calling `canonicalize` just for the path-length-extension alone, so that particular side-effect is de-facto part of the `canonicalize` interface.

…ive, r=alexcrichton

Migrate the toolstate update bot to rust-highfive

Rationale: Only members of the rust-lang organization can mention its teams. That means rust-lang#50434 has no effect if we are still using @kennytm-githubbot.

…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`).