rustdoc: expose #[target_feature] attributes as doc(cfg) flags
This change exposes `#[target_feature(enable = "feat")]` attributes on an item as if they were also `#[doc(cfg(target_feature = "feat"))]` attributes. This gives them a banner on their documentation listing which feature is required to use the item. It also modifies the rendering code for doc(cfg) tags to handle `target_feature` tags. I made it print just the feature name on "short" printings (as in the function listing on a module page), and use "target feature `feat`" in the full banner on the item page itself.
This way, the function listing in `std::arch` shows which feature is required for each function:
Add warning for invalid start of code blocks in rustdoc
Follow up of #48382.
Still two things to consider:
1. Adding test for rustdoc output (but where? In UI or in rustdoc tests?).
2. Try to fix the span issue.
r? @QuietMisdreavus
ci: Print out how long each step takes on CI
This commit updates CI configuration to inform rustbuild that it should print
out how long each step takes on CI. This'll hopefully allow us to track the
duration of steps over time and follow regressions a bit more closesly (as well
as have closer analysis of differences between two builds).
cc #48829
Detect illegal hidden lifetimes in `impl Trait`
This branch fixes#46541 -- however, it presently doesn't build because it also *breaks* a number of existing usages of impl Trait. I'm opening it as a WIP for now, just because we want to move on impl Trait, but I'll try to fix the problem in a bit.
~~(The problem is due to the fact that we apparently infer stricter lifetimes in closures that we need to; for example, if you capture a variable of type `&'a &'b u32`, we will put *precisely* those lifetimes into the closure, even if the closure would be happy with `&'a &'a u32`. This causes the present chance to affect things that are not invariant.)~~ fixed
r? @cramertj
Download the GCC artifacts from the HTTP server instead of FTP server.
Try to bring back the `dist-i686-linux` and `dist-x86_64-linux alt` builders which has mysteriously lost their cache 14 hours ago and stuck forever unable to download `mpfr-2.4.2.tar.bz2` since it keeps getting
```
==> PASV ... couldn't connect to 209.132.180.131 port 10058: Connection timed out
```
Unfortunately we don't have sufficient time to rebuild the cache *and*
distribute everything in `dist-x86_64-linux alt`, the debug assertions are
really slow.
We will re-enable them after the PR has been successfully merged, thus
successfully updating the cache (freeing up 40 minutes), giving us enough
time to build these tools.
We used to make the upvar types in the closure `==` but that was
stronger than we needed. Subtyping suffices, since we are copying the
upvar value into the closure field. This in turn allows us to infer
smaller lifetimes in captured values in some cases (like the example
here), avoiding errors.
Fix ordering of auto-generated trait bounds in rustdoc output
While the order of the where clauses was deterministic, the
ordering of bounds and lifetimes was not. This made the order flip-
flop randomly when new traits and impls were added to libstd.
This PR makes the ordering of bounds and lifetimes deterministic,
and re-enables the test that was causing the issue.
Fixes#49123
