Remove a stack frame from .await calls
The stack frames when `.await`ing one async fn from another currently look like this:
```
12: foo:🅱️:{{closure}}
at src/main.rs:2
13: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
at /home/sfackler/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libcore/future/mod.rs:66
14: core::future::poll_with_context
at /home/sfackler/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libcore/future/mod.rs:84
15: foo:🅰️:{{closure}}
at src/main.rs:6
```
Since the move away from using TLS to pass the Context around, it's now easy to remove frame 14 by removing poll_with_context in favor of calling Future::poll directly. This still leaves the `GenFuture` frame, but that seems significantly harder to deal with.
It also improves diagnostics a bit since they no longer talk about the private poll_with_context function.
Rollup of 8 pull requests
Successful merges:
- #70657 (Allow `try`-blocks in places where an open delim is expected)
- #70947 (tighten CTFE safety net for accesses to globals)
- #70949 (simplify `vec!` macro)
- #71002 (fix target & runtool args order)
- #71082 (ptr: introduce len() method on raw slices)
- #71128 (Remove unused single_step flag)
- #71133 (Tighten time complexity on the doc of sort_by_key)
- #71135 (Update books)
Failed merges:
r? @ghost
Improve async-await/generator obligation errors in some cases
Fixes#68112.
This change is best read one commit at a time (I add a test at the beginning and update it in each change after).
The `test2` function is a case I found while writing the test that we don't handle with this code yet. I don't attempt to fix it in this PR, but it's a good candidate for future work.
r? @davidtwco, @nikomatsakis
allow const generics in const fn
This was explicitly forbidden before. As we were unable to think of a reason
why this should still be the case, this check has been removed.
r? @eddyb
cc @varkor @Centril
Suggest .into() over try_into() when it would work
It would be better to suggest x.into() instead, which is shorter, cannot fail, and doesn't require importing a trait.
Tests have been added and made up to date.
Fixes#70851
