…e methods

It’s not entirely clear from the current documentation what behaviour
calling a method such as `min` on an infinite iterator like `RangeFrom`
is. One might expect this to terminate, but in fact, for infinite
iterators, `min` is always nonterminating (at least in the standard
library). This adds a quick note about this behaviour for clarification.

unlike the other Parse*Error types, ParseCharError didn't have these implemented for whatever reason

Currently if `--out-dir` is set to a non-existent directory, the
compiler will throw unfriendly messages like `error: could not write
output to subdir/example.crate.allocator.rcgu.o: No such file or
directory`, which, while not completely unreadable, isn’t very
user-friendly either. This change creates the directory automatically
if it does not yet exist.

Commit 7ed00ca improved our error reporting by including the target
function in our error messages when there is an argument count mismatch.
A simple example from the UI tests is:

```
error[E0593]: function is expected to take a single 2-tuple as argument, but it takes 0 arguments
  --> $DIR/closure-arg-count.rs:32:53
   |
32 |     let _it = vec![1, 2, 3].into_iter().enumerate().map(foo);
   |                                                     ^^^ expected function that takes a single 2-tuple as argument
...
44 | fn foo() {}
   | -------- takes 0 arguments
```

However, this assumed the target span was always available. This does
not hold true if the target function is in `std` or another crate. A
simple example from rust-lang#48046 is assigning `str::split` to a function type
with a different number of arguments.

Fix by removing all of the labels and suggestions related to the target
span when it's not found.

Fixes rust-lang#48046

Unfortunately left out it means that when the `#![feature(proc_macro)]` flag is
in effect it fails to find `rustc_args_required_const` for expansion. This
version, however, is verified to work with stdsimd's requirements!

This commit disallows acquiring a function pointer to functions tagged as
`#[rustc_args_required_const]`. This is intended to be used as future-proofing
for the stdsimd crate to avoid taking a function pointer to any intrinsic which
has a hard requirement that one of the arguments is a constant value.

…(in mobile too)

Right now the ccache setting is only used for LLVM, but this tweaks it to also
be used for build scripts so C++ builds like `librustc_llvm` can be a bit
speedier.

rust-lang#48048

Right now the `--build` option was accidentally omitted, so we're bootstraping
from `x86_64` to `i686`. In addition to being slower (more compiles) that's not
actually bootstrapping!

cc rust-lang#13226 (the tracking issue)

derive PartialEq and Eq for `ParseCharError`

unlike the other Parse*Error types, ParseCharError didn't have these implemented for whatever reason

…, r=nikomatsakis

Remove unused data structures

Cleanup; as far as I can tell the compiler no longer uses these.

Create a directory for --out-dir if it does not already exist

Currently if `--out-dir` is set to a non-existent directory, the compiler will throw unfriendly messages like `error: could not write output to subdir/example.crate.allocator.rcgu.o: No such file or
directory`, which, while not completely unreadable, isn’t very user-friendly either. This change creates the directory automatically if it does not yet exist.

…lexcrichton

Customizable extended tools

This PR adds `build.tools` option to manage installation of extended rust tools.

By default it doesn't change installation. All tools are built and `rls` and `rustfmt` allowed to fail installation.

If some set of tools chosen only those tools are built and installed without any fails allowed.

It solves some slotting issues with extended build enabled: https://bugs.gentoo.org/show_bug.cgi?id=645498

…-on-target-without-span, r=estebank

Fix ICE for mismatched args on target without span

Commit 7ed00ca improved our error reporting by including the target function in our error messages when there is an argument count mismatch. A simple example from the UI tests is:

```
error[E0593]: function is expected to take a single 2-tuple as argument, but it takes 0 arguments
  --> $DIR/closure-arg-count.rs:32:53
   |
32 |     let _it = vec![1, 2, 3].into_iter().enumerate().map(foo);
   |                                                     ^^^ expected function that takes a single 2-tuple as argument
...
44 | fn foo() {}
   | -------- takes 0 arguments
```

However, this assumed the target span was always available. This does not hold true if the target function is in `std` or another crate. A simple example from rust-lang#48046 is assigning `str::split` to a function type with a different number of arguments.

Fix by omitting all of the labels and suggestions related to the target span when it's not found.

Fixes rust-lang#48046

r? @estebank

…uietMisdreavus

rustdoc: Hide `-> ()` in cross crate inlined Fn* bounds

Update binaryen to fix -Werror with GCC 8

r? @alexcrichton

…lacrum

rustbuild: Pass `ccache` to build scripts

Right now the ccache setting is only used for LLVM, but this tweaks it to also
be used for build scripts so C++ builds like `librustc_llvm` can be a bit
speedier.

…Misdreavus

intra-doc-links: bail early for linky things

r? @QuietMisdreavus

…-proc-macro, r=eddyb

Disallow function pointers to #[rustc_args_required_const]

This commit disallows acquiring a function pointer to functions tagged as
`#[rustc_args_required_const]`. This is intended to be used as future-proofing
for the stdsimd crate to avoid taking a function pointer to any intrinsic which
has a hard requirement that one of the arguments is a constant value.

Note that the first commit here isn't related specifically to this feature, but was necessary to get this working in stdsimd!

…=QuietMisdreavus

Hide theme button under menu in mobile mode and fix top margin issue …

Fixes rust-lang#48060.

r? @QuietMisdreavus

Fix visitation order of calls so that it matches execution order. Fixes rust-lang#48048

r? @nikomatsakis

…p, r=Mark-Simulacrum

ci: Actually bootstrap on i686 dist

Right now the `--build` option was accidentally omitted, so we're bootstraping
from `x86_64` to `i686`. In addition to being slower (more compiles) that's not
actually bootstrapping!

…labnik

Update books for next release

r? @steveklabnik

…tract, r=kennytm

fix typo: substract -> subtract

…richton

Add fetch_nand to atomics

I think this is all fine but I have little familiarity with the atomic code (or libcore in general) so I may have accidentally done something wrong here...

cc rust-lang#13226 (the tracking issue)

A bug was recently fixed in dlmalloc which meant that released memory to the
system accidentally wasn't getting reused, causing programs to be far slower
than they should be!

Introduced in rust-lang#47828 to help track down some bugs, it landed a bit hastily so
this is intended on cleaning it up a bit.

…k-Simulacrum

Update the dlmalloc submodule

A bug was recently fixed in dlmalloc which meant that released memory to the
system accidentally wasn't getting reused, causing programs to be far slower
than they should be!

…chton

fix typos in src/{bootstrap,ci,etc,lib{backtrace,core,fmt_macros}}

via codespell

…kennytm

Explain unusual debugging code in librustc

Introduced in rust-lang#47828 to help track down some bugs, it landed a bit hastily so
this is intended on cleaning it up a bit.

…oc, r=frewsxcv

Document the behaviour of infinite iterators on potentially-computable methods

It’s not entirely clear from the current documentation what behaviour
calling a method such as `min` on an infinite iterator like `RangeFrom`
is. One might expect this to terminate, but in fact, for infinite
iterators, `min` is always nonterminating (at least in the standard
library). This adds a quick note about this behaviour for clarification.