trait objects without an explicit dyn are deprecated

[xiaokang5350]

I use rustc 1.37.0-nightly and report trait objects without an explicit dyn are deprecated warnings

[stepancheg]

Yep, most error were fixed in d6f783e and version 2.6.2, and more muted warnings are needed.

Note that rust-protobuf 2.6 cannot switch to dyn properly because of compatibility with Rust 1.26.

Probably rust-protobuf 2.7 needs to require Rust 1.27 where dyn is stable.

[stepancheg]

rust-protobuf 2.7 (unreleased branch) now works only with Rust 1.27.

[rtsisyk]

Any plans to release 2.7?

[stepancheg]

In about a week. I'm a bit worried that something may break, so if someone wants to help with code review, I'd appreciate that. (Changelog)

[stepancheg]

2.7 is released.

[jakubadamw]

@stepancheg, well, it's released, but the code that gets generated still produces trait objects without an explicit `dyn` are deprecated warnings under Rust >= 1.27. Shouldn't this issue be reopened, then?

I presume that the minimal Rust version required by protoc-rust should go hand in hand with the minimal version the generated code is expected to compile under, correct? Therefore, if the version 2.7 requires Rust 1.27, so should the code it generates, and thereby it can use dyn to eliminate the warnings?

[stepancheg]

@jakubadamw Maybe I'm missing something. Can you please show how to reproduce the problem?

[stepancheg]

(At least show generated code)

[jakubadamw]

@stepancheg, sure! 🙂

https://github.com/jakubadamw/rust-protobuf-414

> cargo build
   Compiling reproduction_414 v0.0.1 (/home/jakub/rust-protobuf-414)
warning: trait objects without an explicit `dyn` are deprecated
  --> src/example.rs:91:26
   |
91 |     fn as_any(&self) -> &::std::any::Any {
   |                          ^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (::std::any::Any)`
   |
   = note: #[warn(bare_trait_objects)] on by default

warning: trait objects without an explicit `dyn` are deprecated
  --> src/example.rs:92:18
   |
92 |         self as &::std::any::Any
   |                  ^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (::std::any::Any)`

warning: trait objects without an explicit `dyn` are deprecated
  --> src/example.rs:94:38
   |
94 |     fn as_any_mut(&mut self) -> &mut ::std::any::Any {
   |                                      ^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (::std::any::Any)`

warning: trait objects without an explicit `dyn` are deprecated
  --> src/example.rs:95:22
   |
95 |         self as &mut ::std::any::Any
   |                      ^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (::std::any::Any)`

warning: trait objects without an explicit `dyn` are deprecated
  --> src/example.rs:97:55
   |
97 |     fn into_any(self: Box<Self>) -> ::std::boxed::Box<::std::any::Any> {
   |                                                       ^^^^^^^^^^^^^^^ help: use `dyn`: `dyn (::std::any::Any)`

    Finished dev [unoptimized + debuginfo] target(s) in 2.98s

[ilblackdragon]

Same here for warning: trait objects without an explicit `dyn` are deprecated with 2.7 and Rust 1.37

[stepancheg]

OK, I see, the problem exists in stable but does not exist in master.

I don't know how to fix in stable.

&dyn ::std::any::Any

This syntax is not valid in edition 2015. And edition 2018 is not available until Rust 1.32.0 (2019-01-17).

Play

So if you know how to fix it, please let me know.

Otherwise, there are two options:

• set minimum supported version 1.32 (it is 1.27 now)
• keep warning as is

Thoughts?

[zsluedem]

I am facing the problem, too.
These warnings(I have 2000+warnings) would heavily trouble people debug.

I am quite new in rust.
How to set minimum supported version 1.32?

[bacek]

I think bumping minimal supported version to 1.32 and switch edition should be fine.

Another options are:

1. to extend Customize object to explicitly enable dyn Trait generation.
2. Detect edition in protoc-rust and generate code for it.

[stepancheg]

Let's set the minimum version to 1.32 since 2.8. Going to do it now.

[stepancheg]

I'll do it now.

[stepancheg]

OK, stupid me.

It's not enough. &dyn Trait cannot be used even in latest stable in edition 2015.

[stepancheg]

Got another idea: df9780f.

[stepancheg]

Published 2.8.0. Please let me know if it doesn't solve the problem.

[bacek]

Are you sure it's compatible with 2015 edition?

[bacek]

Ah. 1.27. Should be all right.

[stepancheg]

Are you sure it's compatible with 2015 edition?

Yes, because the protobuf library and all tests are done against the 2015 edition.

I'm a bit worried about compatibility with 2018 edition. I did basic checks, but there are no automated CI tests.

[bacek]

Works for me in my 2018 edition project.

[feuerste]

Works for me, too, thanks! You may also add the 2.8.0 release in github?

[stepancheg]

@feuerste I forgot to do git push. Thank you for the reminder!