Rename `subst::Kind` to `subst::GenericArg`
And `subst::UnpackedKind` to `subst::GenericArgKind`. Individual variable names (e.g. `kind`) are not renamed, which would be an infeasible mission.
Fixes https://github.com/rust-lang/rust/issues/64352.
r? @eddyb
reserve `impl<T> From<!> for T`
this is necessary for never-type stabilization.
cc #57012#35121
I think we wanted a crater run for this @nikomatsakis?
r? @nikomatsakis
rustdoc: general cleanup
Review should be conducted commit-by-commit.
There are some general cleanup commits in the end, which are somewhat related but can be easily split into another PR, so just let me know.
Use `panic::set_hook` to print the ICE message
This allows custom frontends and backends to override the hook with their own, for example to point people to a different issue tracker.
ICE messages are printed in a slightly different order now. Nightly prints:
```
thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', src/libcore/option.rs:347:21
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0277, E0658.
For more information about an error, try `rustc --explain E0277`.
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.36.0-nightly (08bfe1612 2019-05-02) running on x86_64-unknown-linux-gnu
```
After this PR, rustc prints:
```
thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', src/libcore/option.rs:347:21
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.36.0-dev running on x86_64-unknown-linux-gnu
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0277, E0658.
For more information about an error, try `rustc --explain E0277`.
```
There's not really any reason to not have the visibility default to
inherited, and this saves us the trouble of checking everywhere for
whether we have a visibility or not.
rustdoc: change doctests locating rustc binary
We previously used the "naive" approach of replacing the `current_exe()`'s file name with rustc, but now load from the sysroot by default (`$sysroot/bin/rustc`). The functionality of locating the sysroot overlaps/is the same as the functionality used by codegen backend loading; this ensures that any failure cases we've introduced are not exceeding those, and that improvements to finding the sysroot for loading codegen backends likewise enhance rustdoc.
The second commit adds an unstable `--test-builder` flag to rustdoc, and is largely separate (I can split into separate PR, but it's a simple and related change). This is largely intended for "advanced" users at this point (I'm not sure if we'll ever stabilize it); it permits use of a different rustc binary for rustdoc compilation of doctests than the rustdoc binary used when loading. Note, that this may not be what you want as the parsers and such differ (and rustdoc uses its own libsyntax, etc.). However, I've been told that running doctests in miri may be assisted by this change, so I've implemented it; I'll file a tracking issue for it if there's interest in it (and we land this PR).
Avoid more `Symbol`-to-string operations
These commits avoid various `Symbol`-to-string conversions, by doing more operations directly on `Symbol`s. This requires adding a few more static `Symbol`s to the binary.
r? @petrochenkov
Replace file_stem by file_name in rustdoc markdown
Before this PR, a file name like `some.file.md` will be output to a file named `some.html` with is not correct because the expected output file must be `some.file.html`
