v0.1.x: Apply dyn keywords to avoid fatal warnings on recent nightlies

[dekellum]

This is part (1) of proposed changes in #1348. It may need to wait for stronger motivation, but I wanted to make the changes available. This depends on an MSRV of at least 1.27.0.

Motivation

On the v0.1.x branch, the use of #[deny(warnings)] makes the following warnings fatal on recent nighty compilers (in my case currently: rustc 1.38.0-nightly (83e4eed16 2019-07-14)), when building a local git tree.

error: trait objects without an explicit `dyn` are deprecated
   --> tokio-current-thread/src/scheduler.rs:128:23
    |
128 | struct Task(Spawn<Box<Future<Item = (), Error = ()>>>);
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn Future<Item = (), Error = ()>`
    |
note: lint level defined here
   --> tokio-current-thread/src/lib.rs:2:9
    |
2   | #![deny(warnings, missing_docs, missing_debug_implementations)]
    |         ^^^^^^^^
    = note: #[deny(bare_trait_objects)] implied by #[deny(warnings)]

When built as a dependency of a normal application, cargo passes --cap-lints=allow to rustc (or for cargo -vv, --cap-lints=warn at most), so these are not fatal in that case. The current azure-pipelines CI appears to only test with stable rust (e.g. 1.36.0) or older nightlies, so this hasn't broken CI, yet.

Solution

I applied cargo fix followed by cargo fmt and then filtered through the changes (git add --patch) to isolate these dyn additions. Also this bumps the check-minrust MSRV to 1.27.2, just to hopefully to get CI passing.

[dekellum]

CI will fail on 1.26 (for no dyn support) and 1.27.2 for various reasons, including:

• tempfile 3.1.0 more recent release (dev dependency) is MSRV 1.32.0

• and (new in 1.27.2):

error: unknown lint: `rust_2018_idioms`
 --> tokio-executor/src/lib.rs:4:10
  |
4 | #![allow(rust_2018_idioms)]
  |          ^^^^^^^^^^^^^^^^
  |
note: lint level defined here
 --> tokio-executor/src/lib.rs:1:54
  |
1 | #![deny(missing_docs, missing_debug_implementations, warnings)]
  |                                                      ^^^^^^^^
  = note: #[deny(unknown_lints)] implied by #[deny(warnings)]

• and (also new in 1.27.2):

error: failed to parse manifest at `/home/david/src/tokio/tokio-macros/Cargo.toml`

Caused by:
  editions are unstable

Caused by:
  feature `edition` is required

So it falls back to the question of the proposal MSRV.

[dekellum]

Note that when rust 1.37.0 (stable) is released in ~3 weeks, with the change to warn for lack of dyn (e.g. bare_trait_objects), then CI will presumably be broken for v0.1.x branch.

https://github.com/rust-lang/rust/blob/f2f4c0ed6c247eb8e94845c3e37eb6799ec74885/RELEASES.md

[dekellum]

In 45108c2 removed the allow(rust_2018_idioms) which was selectively applied and caused a failure on 1.27.2 atleast, in order to cargo fix previously missed dyn cases (d350014). CI continues to fail as expected here, but should work when merged with the MSRV increase in #1358.

[dekellum]

CI now passing again, as merged in #1358. @LucioFranco are you good with this (to the extent that MSRV 1.31.0 is accepted) or would you prefer to keep all the warnings in output, but not fail, as in #1368?

[LucioFranco]

@dekellum hey sorry for the delay on this! I've been quite swamped at work and we really want to get the first few alpha versions out. I want you to know I'm not ignoring this at all! I am going to try to give this and the other PRs reviews once we get the alphas out in the next few days. Let me know if you need anything. And again sorry its taking this long 😭

[dekellum]

This was merged by me as part of #1451, squashed and applied to v0.1.x in c9532e4. Closing.