Deny #[cfg] and #[cfg_attr] on generic parameters.
Fix#51279.
Attributes on generic parameters are not expanded, meaning `#[cfg]`, `#[cfg_attr]` and attribute proc macros are entirely ignored on them.
This PR makes using the first two attributes an error, because if they are correctly expanded will affect the AST and change code behavior.
I'm beta-nominating this, because generic parameter attributes are stabilizing in 1.27, and if we did not reserve their usage, we may never be able to repurpose the meaning of these attributes in the Rust 2015 edition.
Remove two redundant .nll.stderr files
It turns out that the diagnostics generated from NLL for these cases are now exactly the same as that produced by AST borrowck, and thus we can just fallback on those `.stderr` files that already exist for AST-borrowck.
Bravo!
(it is a good idea to remove these files, because it slightly reduces the amount of time humans will spend reviewing the .nll.stderr fileset...)
((it *might* be worthwhile trying to change the `compiletest` code to even issue a warning when two such files have equivalent contents... but I am not going so far as to try to implement that right now...))
The only instance of `ObligationForest` in use has an obligation type of
`PendingPredicateObligation`, which contains a `PredicateObligation` and a
`Vec<Ty>`.
`FulfillmentContext::pending_obligations()` calls
`ObligationForest::pending_obligations()`, which clones all the
`PendingPredicateObligation`s. But the `Vec<Ty>` field of those cloned
obligations is never touched.
This patch changes `ObligationForest::pending_obligations()` to
`map_pending_obligations` -- which gives callers control about which part
of the obligation to clone -- and takes advantage of the change to avoid
cloning the `Vec<Ty>`. The change speeds up runs of a few rustc-perf
benchmarks, the best by 1%.
`process_predicates` returns a
`Result<Option<Vec<PredicateObligation>>>`. `process_obligation` calls
it and then fiddles with the output (using `map`, `map`, `into_iter`,
`collect`) to produce a a
`Result<Option<Vec<PendingPredicateObligation>>>`.
This function is sufficiently hot that the fiddling is expensive. It's
much better for `process_predicate` to directly return a
`Result<Option<Vec<PendingPredicateObligation>>>` because `Ok(None)`
accounts for ~90% of the results, and `Ok(vec![])` accounts for another
~5%.
Add Future and task system to the standard library
This adds preliminary versions of the `std::future` and `std::task` modules in order to unblock development of async/await (https://github.com/rust-lang/rust/issues/50547). These shouldn't be considered as final forms of these libraries-- design questions about the libraries should be left on https://github.com/rust-lang/rfcs/pull/2418. Once that RFC (or a successor) is merged, these APIs will be adjusted as necessary.
r? @aturon
Accept `..` in incorrect position to avoid further errors
We currently give a specific message when encountering a `..` anywhere
other than the end of a pattern. Modify the parser to accept it (while
still emitting the error) so that we don't also trigger "missing fields
in pattern" errors afterwards.
Add suggestions to either remove trailing `,` or moving the `..` to the
end.
Follow up to #49268.
