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Implement a explicit_generic_args_with_impl_trait feature gate #86176

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merged 1 commit into from
Aug 2, 2021

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nbdd0121
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@nbdd0121 nbdd0121 commented Jun 9, 2021

Implements #83701

When this gate is enabled, explicit generic arguments can be specified even if impl Trait is used in argument position. Generic arguments can only be specified for explicit generic parameters but not for the synthetic type parameters from impl Trait

So code like this will be accepted:

#![feature(explicit_generic_args_with_impl_trait)]

fn foo<T: ?Sized>(_f: impl AsRef<T>) {}
fn main() {
    foo::<str>("".to_string());
}

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r? @steveklabnik

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 9, 2021
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bors commented Jun 10, 2021

☔ The latest upstream changes (presumably #80080) made this pull request unmergeable. Please resolve the merge conflicts.

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@crlf0710 crlf0710 added A-impl-trait Area: `impl Trait`. Universally / existentially quantified anonymous types with static dispatch. T-lang Relevant to the language team, which will review and decide on the PR/issue. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 26, 2021
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r? @matthewjasper

@JohnCSimon JohnCSimon added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 12, 2021
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bors commented Jul 27, 2021

☔ The latest upstream changes (presumably #83484) made this pull request unmergeable. Please resolve the merge conflicts.

@nbdd0121 nbdd0121 force-pushed the explicit-generic-args branch 2 times, most recently from 15a1422 to 35b80d9 Compare July 28, 2021 01:07
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bors commented Jul 28, 2021

☔ The latest upstream changes (presumably #86735) made this pull request unmergeable. Please resolve the merge conflicts.

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r? @bjorn3 as per GitHub suggestions

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bjorn3 commented Jul 28, 2021

I have no experience with the typechecker, maybe

r? @lcnr

(another github suggestion)

@rust-highfive rust-highfive assigned lcnr and unassigned bjorn3 Jul 28, 2021
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I will take this review if @lcnr can't.

That being said, I think it's prudent to get a sign off from the lang team here. I imagine this probably falls under the "make more reversible decisions" part of the initiative process. So probably just need someone to give the okay. So cc @rust-lang/lang

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I agree---since this is nightly-only, I think it's fine to go ahead with it.

I'll nominate this for consideration at a future meeting, but in the interim, go ahead.

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bors commented Jul 30, 2021

☔ The latest upstream changes (presumably #87237) made this pull request unmergeable. Please resolve the merge conflicts.

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A couple nits, but r=me for this after those are addressed.

#83701 needs modified to "become" a tracking issue before/when this lands (or a new issue could be opened)

@@ -687,6 +687,9 @@ declare_features! (
/// Trait upcasting is casting, e.g., `dyn Foo -> dyn Bar` where `Foo: Bar`.
(incomplete, trait_upcasting, "1.56.0", Some(65991), None),

/// Allows explicit generic arguments specification with `impl Trait` present.
(active, explicit_generic_args_with_impl_trait, "1.56.0", Some(83701), None),
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I suppose we can just co-opt that issue to be a tracking issue, yeah.

@@ -459,7 +459,28 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {

let default_counts = gen_params.own_defaults();
let param_counts = gen_params.own_counts();
let named_type_param_count = param_counts.types - has_self as usize;
let synth_type_param_count = if tcx.features().explicit_generic_args_with_impl_trait {
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I'd like a small comment here just explaining what we're doing.

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Done

src/test/ui/impl-trait/explicit-generic-args-for-impl.rs Outdated Show resolved Hide resolved
@@ -0,0 +1,9 @@
error[E0632]: cannot provide explicit generic arguments when `impl Trait` is used in argument position
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...in fact, I imagine the longer for that part of the diagnostic will probably co-opt some of this logic

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jackh726 commented Aug 2, 2021

r? @jackh726

@rust-highfive rust-highfive assigned jackh726 and unassigned lcnr Aug 2, 2021
@jackh726 jackh726 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-review Status: Awaiting review from the assignee but also interested parties. labels Aug 2, 2021
When this gate is enabled, explicit generic arguments can be specified even
if `impl Trait` is used in argument position. Generic arguments can only be
specified for explicit generic parameters but not for the synthetic type
parameters from  `impl Trait`
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jackh726 commented Aug 2, 2021

@bors r+

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bors commented Aug 2, 2021

📌 Commit 9b90e7e has been approved by jackh726

@bors 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 Aug 2, 2021
bors added a commit to rust-lang-ci/rust that referenced this pull request Aug 2, 2021
Rollup of 6 pull requests

Successful merges:

 - rust-lang#86176 (Implement a `explicit_generic_args_with_impl_trait` feature gate)
 - rust-lang#87654 (Add documentation for the order of Option and Result)
 - rust-lang#87659 (Fix invalid suggestions for non-ASCII characters in byte constants)
 - rust-lang#87673 (Tweak opaque type mismatch error)
 - rust-lang#87687 (Inline some macros)
 - rust-lang#87690 (Add missing "allocated object" doc link to `<*mut T>::add`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 14f3418 into rust-lang:master Aug 2, 2021
@rustbot rustbot added this to the 1.56.0 milestone Aug 2, 2021
@nbdd0121 nbdd0121 deleted the explicit-generic-args branch August 2, 2021 22:14
Dylan-DPC added a commit to Dylan-DPC/rust that referenced this pull request Feb 26, 2022
…ackh726

Provide extra note if synthetic type args are specified

Implement the unresolved question in rust-lang#83701 as suggested in rust-lang#86176 (comment).

r? `@jackh726`
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Feb 26, 2022
…ackh726

Provide extra note if synthetic type args are specified

Implement the unresolved question in rust-lang#83701 as suggested in rust-lang#86176 (comment).

r? ``@jackh726``
Dylan-DPC added a commit to Dylan-DPC/rust that referenced this pull request Jun 11, 2022
…1,nagisa

Stabilize explicit_generic_args_with_impl_trait

This is a stabilisation PR for `explicit_generic_args_with_impl_trait`.

* [tracking issue](rust-lang#83701)
  - [Stabilisation report](rust-lang#83701 (comment))
  - [FCP entered](rust-lang#83701 (comment))
* [implementation PR](rust-lang#86176)
* [Reference PR](rust-lang/reference#1212)
* There is no mention of using the turbofish operator in the book (other than an entry in the operator list in the appendix), so there is no documentation to change/add there, unless we felt like we should add a section on using turbofish, but that seems orthogonal to `explicit_generic_args_with_impl_trait`
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