Replaced wrong test with the correct mcve

[SarthakSingh31]

Closes #89008.

The old test was wrong and the compiler was correctly raising an error. The bug in the issue was resolved at some point but due to the wrong test the issue was never closed.

This pr replaces that test with the correct MCVE (made by @jackh726).

The error raised by the bug changed between when the bug was posted (2021-09-08) and when the MCVE was posted (2021-10-23).
I ran them both through nightly-2021-09-08 and they produce identical error messages. They also produce identical but different from before error messages when ran through nightly-2021-10-23.

Error message with nightly-2021-09-08

The code with the original bug report:

error[E0277]: the size for values of type `Repr` cannot be known at compilation time
--> src/main.rs:23:43
 |
23 |     fn line_stream<'a, Repr>(&'a self) -> Self::LineStreamFut<'a, Repr> {
 |                        ----               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
 |                        |
 |                        this type parameter needs to be `std::marker::Sized`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `test-234234` due to previous error

MVCE:

error[E0277]: the size for values of type `Repr` cannot be known at compilation time
  --> src/main.rs:30:43
   |
30 |     fn line_stream<'a, Repr>(&'a self) -> Self::LineStreamFut<'a, Repr> {
   |                        ----               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
   |                        |
   |                        this type parameter needs to be `std::marker::Sized`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `test-234234` due to previous error

Error message with nightly-2021-10-23

The code with the original bug report:

error[E0271]: type mismatch resolving `<impl futures::Future as futures::Future>::Output == impl futures::Stream`
  --> src/main.rs:23:43
   |
19 |     type LineStream<'a, Repr> = impl Stream<Item = Repr>;
   |                                 ------------------------ the expected opaque type
...
23 |     fn line_stream<'a, Repr>(&'a self) -> Self::LineStreamFut<'a, Repr> {
   |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected opaque type, found struct `futures::stream::Empty`
   |
   = note: expected opaque type `impl futures::Stream`
                   found struct `futures::stream::Empty<_>`

error: could not find defining uses
  --> src/main.rs:19:33
   |
19 |     type LineStream<'a, Repr> = impl Stream<Item = Repr>;
   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0271`.
error: could not compile `test-234234` due to 2 previous errors

MCVE:

error[E0271]: type mismatch resolving `<impl Future as Future>::Output == impl Stream`
  --> src/main.rs:30:43
   |
28 |     type LineStream<'a, Repr> = impl Stream<Item = Repr>;
   |                                 ------------------------ the expected opaque type
29 |     type LineStreamFut<'a, Repr> = impl Future<Output = Self::LineStream<'a, Repr>>;
30 |     fn line_stream<'a, Repr>(&'a self) -> Self::LineStreamFut<'a, Repr> {
   |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected opaque type, found struct `Empty`
   |
   = note: expected opaque type `impl Stream`
                   found struct `Empty<_>`

error: could not find defining uses
  --> src/main.rs:28:33
   |
28 |     type LineStream<'a, Repr> = impl Stream<Item = Repr>;
   |                                 ^^^^^^^^^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0271`.
error: could not compile `test-234234` due to 2 previous errors

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Mark-Simulacrum (or someone else) soon.

Please see the contribution instructions for more information.

[jackh726]

Thank you!

@bors r+ rollup

[bors]

📌 Commit cc6ad45 has been approved by jackh726

It is now in the queue for this repository.