Suggest to add lifetime constraint at explicit ouput of functions

Closes #62097

Stabilize `!` in Rust 1.41.0

This PR stabilizes the `never_type` (written `!`). The type represents computations that we know diverge in the type system and therefore has no values / inhabitants / elements / members.

The current nightly version is 1.40.0 which will become stable on 2019-12-19.

Tracking issue: https://github.com/rust-lang/rust/issues/35121.
Closes https://github.com/rust-lang/rust/issues/57012.
Closes https://github.com/rust-lang/rust/issues/58184.
Original stabilization report: https://github.com/rust-lang/rust/issues/57012#issuecomment-452398538

Additional notes:

- In #62661 we reserved `impl<T> From<!> for T` so this concern should be resolved.
- The type inference fallback change is moved to `#![feature(never_type_fallback)]` (https://github.com/rust-lang/rust/issues/65992).
- You can find all of the tests referencing `never_type` in this PR which also reorganizes these tests whereas they were more scattered before.

r? @nikomatsakis

Also remove `never_type` the feature-gate test.

Rollup of 7 pull requests

Successful merges:

 - #66060 (Making ICEs and test them in incremental)
 - #66298 (rustdoc: fixes #64305: disable search field instead of hidding it)
 - #66457 (Just derive Hashstable in librustc)
 - #66496 (rustc_metadata: Privatize more things)
 - #66514 (Fix selected crate search filter)
 - #66535 (Avoid ICE when `break`ing to an unreachable label)
 - #66573 (Ignore run-make reproducible-build-2 on Mac)

Failed merges:

r? @ghost

Ignore run-make reproducible-build-2 on Mac

Ignore run-make reproducible-build-2 on Mac (we already ignore it on Windows).

Until we can dedicate resources to fixing this properly, I think we are best off just ignoring this test on platforms/contexts where it does not matter as much.

cc #66568

Avoid ICE when `break`ing to an unreachable label

Fix #62480.

Fix selected crate search filter

Fixes #62929.

r? @kinnison

rustc_metadata: Privatize more things

Continuation of https://github.com/rust-lang/rust/pull/66056.

The most notable change here is that `CrateMetadata` is moved from `cstore.rs` to `decoder.rs`.
Most of uses of `CrateMetadata` fields are in the decoder and uses of `root: CrateRoot` and other fields are so intertwined with each other that it would be hard to move a part of them into `cstore.rs` to privatize `CrateMetadata` fields, so we are going the other way round.

`cstore.rs` can probably be dismantled now, but I'll leave this to some other day.
Similarly, remaining `CrateMetadata` fields can be privatized by introducing some getter/setter methods, but not today.

r? @EddyB

Just derive Hashstable in librustc

Split out of #66279

r? @Zoxc

rustdoc: fixes #64305: disable search field instead of hidding it

The result seems to be ok but I wasn't entirely sure how to get there. I tried to stay generic a bit but maybe it's not required at all.

@GuillaumeGomez
Signed-off-by: NMaxime “pep” Buquet <pep@bouah.net>

Making ICEs and test them in incremental

This adds:
 - A way to make the compiler ICE
 - A way to check for ICE in `cfail` tests with `should-ice`
 - A regression test for issue #65401

I am not sure the attribute added `should-ice` is the best for this job

Rollup of 8 pull requests

Successful merges:

 - #65665 (Update Source Code Pro and include italics)
 - #66478 (rustc_plugin: Remove the compatibility shim)
 - #66497 (Fix #53820)
 - #66526 (Add more context to `async fn` trait error)
 - #66532 (Generate DWARF address ranges for faster lookups)
 - #66546 (Remove duplicate function)
 - #66548 ([RISCV] Disable Atomics on all Non-A RISC-V targets)
 - #66553 (remove HermitCore leftovers from sys/unix)

Failed merges:

r? @ghost

Until we can dedicate resources to fixing this properly, I think we are
best off just ignoring this test on platforms/contexts where it does not
matter as much.

remove HermitCore leftovers from sys/unix

HermitCore support is already moved to the directory "sys/hermit". => remove leftovers

[RISCV] Disable Atomics on all Non-A RISC-V targets

In a `TargetOptions` configuration, `max_atomic_width: None` causes `max_atomic_width()` to return `Some(target_pointer_width)`. So, contrary to assumptions, `max_atomic_width: None` means you do have atomic support!

RISC-V's rv32i and rv32imc do not have architectural support for atomic memory accesses of any size, because they do not include the `A` architecture extension. This means the values in the target definition should be `Some(0)`.

This bug has been observed via a build failure with oreboot/oreboot#191, where LLVM was still generating libcalls for atomic operations. According to rust-lang/compiler-builtins, "Rust only exposes atomic types on platforms that support them, and therefore does not need to fall back to software implementations." - so this PR tries to bring rustc inline with this decision.

This commit also removes the outdated bug link, which references a now irrelevant GCC bug.

I will likely also have to revisit the `min_atomic_width` of all the RISC-V targets so they are correct and match what the hardware is capable of (which is more restricted than one might imagine).

r? @alexcrichton

Remove duplicate function

Function `source_name` declared in file

[src/librustc_driver/lib.rs](https://github.com/rust-lang/rust/blob/master/src/librustc_driver/lib.rs#L87)

is a duplicate of the function by the same name declared in file

[src/librustc/session/config.rs](https://github.com/rust-lang/rust/blob/master/src/librustc/session/config.rs#L511)

Generate DWARF address ranges for faster lookups

This adds a new option `-Zgenerate-arange-section`, enabled by default,
corresponding to LLVM's `-generate-arange-section`. This creates a
`.debug_aranges` section with DWARF address ranges, which some tools
depend on to optimize address lookups (elfutils [22288], [25173]).

This only has effect when debuginfo is enabled, and the additional data
is small compared to the other debug sections. For example, libstd.so
with full debuginfo is about 11MB, with just 61kB in aranges.

[22288]: https://sourceware.org/bugzilla/show_bug.cgi?id=22288
[25173]: https://sourceware.org/bugzilla/show_bug.cgi?id=25173

Closes #45246.
r? @michaelwoerister

Add more context to `async fn` trait error

Follow up to #65937. Fix #65899.

Fix #53820

This fixes ICE #53820 by being more clever when matching large arrays with slice patterns.
In particular, it avoids treating large arrays like large tuples, and instead reuses the `VarLenSlice` constructor behaviour to only consider as little values as needed.
As a side-effect, such matches also get improved diagnostics, by reporting `[true, ..]` missing instead of `[true, _, _, _, _, _, _, _]`.

rustc_plugin: Remove the compatibility shim

The compatibility crate was introduced in https://github.com/rust-lang/rust/pull/62727 to migrate Cargo and some other tools, but now it's no longer necessary.

Update Source Code Pro and include italics

Fixes #65502.

A few notes:
  * As stated in #65502, this does increase the download size.
  * Since this PR changes the font set, I think docs.rs would have to be updated if this PR is merged.
  * The fonts have a double extension (.ttf.woff); this is to keep the names consistent with the upstream font release which does that to distinguish these from the .otf.woff files ([Source Code Pro otf renders poorly on older Windows system apps](https://github.com/adobe-fonts/source-code-pro/issues/25#issuecomment-9019600)).

Do not ICE on trait aliases with missing obligations

Fix #65673.

Signed-off-by: NMaxime “pep” Buquet <pep@bouah.net>

Generic arg disambiguation

Using the tactic suggested by @petrochenkov in https://github.com/rust-lang/rust/issues/60804#issuecomment-516769465 and on [zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/generic.20argument.20disambiguation), this change checks type arguments to see if they are really incorrectly-parsed const arguments.

it should be noted that `segments.len() == 1 && segments[0].arg.is_none()` was reduced to `segments.len() == 1` as suggested by @petrochenkov in [zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/generic.20argument.20disambiguation/near/177848002). This change allowed a few more existing tests to have their braces removed.

There are a couple of "problems" with these changes that I should note. First, there was a regression in the error messages found in "src/test/ui/privacy-ns1.rs" and "src/test/ui/privacy-ns1.rs". Second, some braces were unable to be removed from "src/test/ui/const-generics/fn-const-param-infer.rs". Those on line 24 caused the statement to stop equating when removed, and those on line 20 cause a statement that should not equate to produce no error when removed.

I have not looked further into any of these issues yet, though I would be willing to look into them before landing this. I simply wanted to get some other eyes on this before going further.

Fixes #60804

cc @varkor @jplatte