Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Descriptive error when users try to combine RPITIT/AFIT with specialization #108551

Merged
merged 1 commit into from
Mar 1, 2023

Conversation

compiler-errors
Copy link
Member

Previously we failed with some esoteric error like:

error[E0053]: method `foo` has an incompatible type for trait
  --> $DIR/dont-project-to-specializable-projection.rs:14:35
   |
LL |     default async fn foo(_: T) -> &'static str {
   |                                   ^^^^^^^^^^^^ expected associated type, found future
   |
note: type in trait
  --> $DIR/dont-project-to-specializable-projection.rs:10:27
   |
LL |     async fn foo(_: T) -> &'static str;
   |                           ^^^^^^^^^^^^
   = note: expected signature `fn(_) -> impl Future<Output = &'static str>`
              found signature `fn(_) -> impl Future<Output = &'static str>`

Now we error like:

error: async associated function in trait cannot be specialized
  --> $DIR/dont-project-to-specializable-projection.rs:14:5
   |
LL |     default async fn foo(_: T) -> &'static str {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: specialization behaves in inconsistent and surprising ways with `#![feature(async_fn_in_trait)]`, and for now is disallowed

@rustbot
Copy link
Collaborator

rustbot commented Feb 28, 2023

r? @Nilstrieb

(rustbot has picked a reviewer for you, use r? to override)

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Feb 28, 2023
@compiler-errors
Copy link
Member Author

r? types

@rustbot rustbot assigned oli-obk and unassigned Noratrieb Feb 28, 2023
@@ -18,6 +18,14 @@ LL | fn bar(&self) -> impl Sized;
= note: expected signature `fn(&U) -> impl Sized`
Copy link
Member Author

@compiler-errors compiler-errors Feb 28, 2023

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This fails to be replaced by the other message because we're not actually even assembling a ProjectionCandidate::ImplTraitInTrait here. Oh well, not that big of a deal.

@oli-obk
Copy link
Contributor

oli-obk commented Feb 28, 2023

@bors r+ rollup

@bors
Copy link
Contributor

bors commented Feb 28, 2023

📌 Commit ecac8fd has been approved by oli-obk

It is now in the queue for this repository.

@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-review Status: Awaiting review from the assignee but also interested parties. labels Feb 28, 2023
Dylan-DPC added a commit to Dylan-DPC/rust that referenced this pull request Feb 28, 2023
…=oli-obk

Descriptive error when users try to combine RPITIT/AFIT with specialization

Previously we failed with some esoteric error like:

```
error[E0053]: method `foo` has an incompatible type for trait
  --> $DIR/dont-project-to-specializable-projection.rs:14:35
   |
LL |     default async fn foo(_: T) -> &'static str {
   |                                   ^^^^^^^^^^^^ expected associated type, found future
   |
note: type in trait
  --> $DIR/dont-project-to-specializable-projection.rs:10:27
   |
LL |     async fn foo(_: T) -> &'static str;
   |                           ^^^^^^^^^^^^
   = note: expected signature `fn(_) -> impl Future<Output = &'static str>`
              found signature `fn(_) -> impl Future<Output = &'static str>`
```

Now we error like:

```
error: async associated function in trait cannot be specialized
  --> $DIR/dont-project-to-specializable-projection.rs:14:5
   |
LL |     default async fn foo(_: T) -> &'static str {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: specialization behaves in inconsistent and surprising ways with `#![feature(async_fn_in_trait)]`, and for now is disallowed
```
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Feb 28, 2023
…=oli-obk

Descriptive error when users try to combine RPITIT/AFIT with specialization

Previously we failed with some esoteric error like:

```
error[E0053]: method `foo` has an incompatible type for trait
  --> $DIR/dont-project-to-specializable-projection.rs:14:35
   |
LL |     default async fn foo(_: T) -> &'static str {
   |                                   ^^^^^^^^^^^^ expected associated type, found future
   |
note: type in trait
  --> $DIR/dont-project-to-specializable-projection.rs:10:27
   |
LL |     async fn foo(_: T) -> &'static str;
   |                           ^^^^^^^^^^^^
   = note: expected signature `fn(_) -> impl Future<Output = &'static str>`
              found signature `fn(_) -> impl Future<Output = &'static str>`
```

Now we error like:

```
error: async associated function in trait cannot be specialized
  --> $DIR/dont-project-to-specializable-projection.rs:14:5
   |
LL |     default async fn foo(_: T) -> &'static str {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: specialization behaves in inconsistent and surprising ways with `#![feature(async_fn_in_trait)]`, and for now is disallowed
```
bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 1, 2023
…iaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#108297 (Exit when there are unmatched delims to avoid noisy diagnostics)
 - rust-lang#108531 (rustdoc: Show that repeated expression arrays can be made with constant values)
 - rust-lang#108536 (Update books)
 - rust-lang#108550 (Remove the `capture_disjoint_fields` feature)
 - rust-lang#108551 (Descriptive error when users try to combine RPITIT/AFIT with specialization)
 - rust-lang#108554 (Only look for param in item's generics if it actually comes from generics)
 - rust-lang#108555 (Fix a race in the query system)
 - rust-lang#108558 (add missing feature in core/tests)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit b2dc8c5 into rust-lang:master Mar 1, 2023
@rustbot rustbot added this to the 1.69.0 milestone Mar 1, 2023
@compiler-errors compiler-errors deleted the rpitit-bad-spec branch August 11, 2023 20:18
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
Projects
None yet
Development

Successfully merging this pull request may close these issues.

5 participants