b2dc8c505c
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
```
|
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| .. | ||
| assembly | ||
| auxiliary | ||
| codegen | ||
| codegen-units | ||
| debuginfo | ||
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| pretty | ||
| run-make | ||
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| COMPILER_TESTS.md | ||