Various fixes to trait alias feature #55994

alexreg · 2018-11-16T01:59:40Z

Disallows multiple regular traits in trait objects when trait aliases used, ensuring code like the following fails to compile.

#![feature(trait_alias)]

trait Foo = std::io::Read + std::io::Write;

fn main() {
    let foo: Box<dyn Foo>;
}

Implemented cross-crate usage of trait aliases. They know get properly encoded and decoded in crate metadata. Added test.
Introduces the DUPLICATE_AUTO_TRAITS_IN_BOUNDS lint (warn-by-default).
Added test for issue ICE with trait aliases and use items #56488. (Appears to be false positive.)

Issue fixes

CC @nikomatsakis @scalexm

rust-highfive · 2018-11-16T01:59:50Z

r? @nikomatsakis

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alexreg · 2018-11-16T05:28:01Z

I still want to improve error messages a bit, but this is nearly ready. Feel free to review.

alexreg · 2018-11-17T19:19:16Z

Ready for review and (hopefully) merge now, I think.

nikomatsakis

Looks great! Left one nit (on the test)

src/librustc/traits/util.rs

src/test/ui/error-codes/E0225.rs

nikomatsakis · 2018-11-20T19:09:43Z

@bors r+

bors · 2018-11-20T19:09:44Z

📌 Commit c180d7ce09bba0ab7c97365e2a1d1c33face2618 has been approved by nikomatsakis

bors · 2018-11-23T14:29:02Z

☔ The latest upstream changes (presumably #55808) made this pull request unmergeable. Please resolve the merge conflicts.

alexreg · 2018-11-24T03:25:01Z

What on Earth... this didn't merge yet?!

Mark-Simulacrum · 2018-11-25T00:13:56Z

@bors r=nikomatsakis

bors · 2018-11-25T00:13:57Z

📌 Commit 4fb40da has been approved by nikomatsakis

See <rust-lang#55994 (comment)> for details.

alexreg · 2019-01-03T17:16:50Z

@nikomatsakis Okay, finally reading for r+ I think! Linting has been removed; that will be addressed in a separated PR.

src/librustc/traits/util.rs

src/librustc_typeck/astconv.rs

bors · 2019-01-05T06:18:57Z

☔ The latest upstream changes (presumably #56837) made this pull request unmergeable. Please resolve the merge conflicts.

stokhos · 2019-01-14T04:32:29Z

Ping from triage @alexreg : Have you been able to make any progress on this PR?

alexreg · 2019-01-14T05:04:36Z

@stokhos 2 and 4 have been factored out into a separate PR by @nikomatsakis (and merged), while he is still working on 1, because it's slightly non-trivial. 3 is postponed for now.

Perhaps we should close this PR?

nikomatsakis · 2019-01-15T17:17:27Z

Let's go ahead and close this PR, the relevant commits are in other branches by now.

@alexreg

…nikomatsakis make trait-aliases work across crates This is rebase of a small part of @alexreg's PR rust-lang#55994. It focuses just on the changes that integrate trait aliases properly into crate metadata, excluding the stylistic edits and the trait objects. The stylistic edits I also rebased and can open a separate PR. The trait object stuff I found challenging and decided it basically needed to be reimplemented. For now I've excluded it. Since this is really @alexreg's work (I really just rebased) I am going to make it r=me once it is working. Fixes rust-lang#56488. Fixes rust-lang#57023.

@Centril

…=oli-obk Ban multi-trait objects via trait aliases Obviously, multi-trait objects are not normally supported, so they should not be supported via trait aliases. This has been factored out from the previous PR #55994 (see point 1). r? @Centril CC @nikomatsakis

@Centril

…=oli-obk Ban multi-trait objects via trait aliases Obviously, multi-trait objects are not normally supported, so they should not be supported via trait aliases. This has been factored out from the previous PR #55994 (see point 1). r? @Centril CC @nikomatsakis ------------------ ### RELNOTES: We now allow `dyn Send + fmt::Debug` with equivalent semantics to `dyn fmt::Debug + Send`. That is, the order of the mentioned traits does not matter wrt. principal/not-principal traits. This is a small change that might deserve a mention in the blog post because it is a language change but most likely not. See https://github.com/rust-lang/rust/blob/ce2ee305f9165c037ecddddb5792588a15ff6c37/src/test/ui/traits/wf-trait-object-reverse-order.rs. // @Centril

rust-highfive assigned nikomatsakis Nov 16, 2018

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alexreg force-pushed the fix-trait-alias-1 branch from 400a7ad to 6d33374 Compare November 16, 2018 02:03

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alexreg changed the title ~~[WIP] Disallows multiple regular traits in trait objects when trait aliases used~~ [WIP] Disallow multiple regular traits in trait objects when trait aliases used Nov 16, 2018

alexreg force-pushed the fix-trait-alias-1 branch from 6d33374 to abb21ad Compare November 16, 2018 05:27

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alexreg force-pushed the fix-trait-alias-1 branch from abb21ad to 10c8e72 Compare November 17, 2018 19:16

alexreg changed the title ~~[WIP] Disallow multiple regular traits in trait objects when trait aliases used~~ Disallow multiple regular traits in trait objects when trait aliases used Nov 17, 2018

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alexreg force-pushed the fix-trait-alias-1 branch from 10c8e72 to ddb7ca3 Compare November 18, 2018 02:18

nikomatsakis approved these changes Nov 20, 2018

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 20, 2018

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Nov 23, 2018

alexreg force-pushed the fix-trait-alias-1 branch from c180d7c to adbab16 Compare November 24, 2018 03:31

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alexreg force-pushed the fix-trait-alias-1 branch from adbab16 to 4fb40da Compare November 24, 2018 04:25

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 25, 2018

Alexander Regueiro added 10 commits January 2, 2019 22:03

Disallow multi-trait objects via trait aliases.

4705c29

Report all intermediate expansions of trait aliases.

f62872f

Fixed rebase fallout.

70fafb1

Lint duplicate auto traits in trait objects.

f9b8d8e

Added test for issue rust-lang#56488.

e7c17a8

Implemented cross-crate usage of trait aliases.

8fa33fe

Converted future-compatibility warning lint to regular lint.

c650069

See <rust-lang#55994 (comment)> for details.

Several small fixes

571182a

Updated tests and stderr files.

bed5ff4

Fixed nits raised in review.

a8e7baa

alexreg force-pushed the fix-trait-alias-1 branch from 174915c to d56ef2d Compare January 3, 2019 04:50

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alexreg force-pushed the fix-trait-alias-1 branch from d56ef2d to 14e8c6a Compare January 3, 2019 15:11

Cosmetic improvements and fixes to stderr files

d246b2c

alexreg force-pushed the fix-trait-alias-1 branch from 14e8c6a to d246b2c Compare January 3, 2019 17:15

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nikomatsakis mentioned this pull request Jan 10, 2019

make trait-aliases work across crates #57502

Merged

nikomatsakis closed this Jan 15, 2019

alexreg added A-trait-system Area: Trait system F-trait_alias `#![feature(trait_alias)]` labels Nov 24, 2019

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Various fixes to trait alias feature #55994

Various fixes to trait alias feature #55994

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nikomatsakis commented Jan 15, 2019

Various fixes to trait alias feature #55994

Various fixes to trait alias feature #55994

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