the `InvocationCollector` and `PlaceholderExpander` folds.

README.md: fix a "\" in table heading to be "/"

Improve char_lit's readability and speed

This is my first contribution to rustc. Please let me know if I've done anything wrong. (I ran `make tidy` before making the pull request.)

use `adt::trans_const` when translating constant closures and tuples

The previous way dropped padding on the floor.

Fixes #36401

r? @EddyB

Allow setting --docdir

This will allow setting `--docdir` during configure, this is useful because not all linux distributions install documentation to `/usr/share/doc`.  For example in Slackware documentation is installed to `/usr/doc/$PRGNAM-$VERSION` and `/usr/share/doc` is a symlink to `/usr/doc`.

To use this `./configure --docdir=/usr/doc/$PRGNAM-$VERSION` can be used.

This reduces the time taken to run
`rustc -Zparse-only rustc-benchmarks/issue-32278-big-array-of-strings`
from 0.18s to 0.15s on my machine, and reduces the number of
instructions (as measured by Cachegrind) from 1.34B to 1.01B.

With the change applied, the time to fully compile that benchmark is
1.96s, so this is a 1.5% improvement.

This makes the function more concise and easier to understand.

Work around pointer aliasing issue in Vec::extend_from_slice, extend_with_element

Due to missing noalias annotations for &mut T in general (issue #31681),
in larger programs extend_from_slice and extend_with_element may both
compile very poorly. What is observed is that the .set_len() calls are
not lifted out of the loop, even for `Vec<u8>`.

Use a local length variable for the Vec length instead, and use a scope
guard to write this value back to self.len when the scope ends or on
panic. Then the alias analysis is easy.

This affects extend_from_slice, extend_with_element, the vec![x; n]
macro, Write impls for Vec<u8>, BufWriter, etc (but may / may not
have triggered since inlining can be enough for the compiler to get it right).

Fixes #32155
Fixes #33518
Closes #17844

Use LLVM_COMPONENTS to run tests just for supported targets

This is already done for simd-ffi test, but not for atomic-lock-free test.

Fix #35023.

Fixes #36401

Point macros 1.1 errors to the input item

Moved from https://github.com/alexcrichton/rust/pull/6 to continue discussion. Fixes #36218.

Before:

```rust
error[E0106]: missing lifetime specifier
  --> src/main.rs:10:10
   |
10 | #[derive(Serialize, Deserialize)]
   |          ^ expected lifetime parameter

error[E0038]: the trait `T` cannot be made into an object
  --> src/main.rs:15:15
   |
15 | #[derive(Serialize, Deserialize)]
   |          ^^^^^^^^^^ the trait `T` cannot be made into an object
```

After:

```rust
error[E0106]: missing lifetime specifier
  --> src/main.rs:11:1
   |
11 | struct A {
   | ^ expected lifetime parameter

error[E0038]: the trait `T` cannot be made into an object
  --> src/main.rs:16:1
   |
16 | struct B<'a> {
   | ^ the trait `T` cannot be made into an object
```

Add s390x support

This adds support for building the Rust compiler and standard
library for s390x-linux, allowing a full cross-bootstrap sequence
to complete.  This includes:

- Makefile/configure changes to allow native s390x builds
- Full Rust compiler support for the s390x C ABI
  (only the non-vector ABI is supported at this point)
- Port of the standard library to s390x
- Update the liblibc submodule to a version including s390x support
- Testsuite fixes to allow clean "make check" on s390x

Caveats:

- Resets base cpu to "z10" to bring support in sync with the default
  behaviour of other compilers on the platforms.  (Usually, upstream
  supports all older processors; a distribution build may then chose
  to require a more recent base version.)  (Also, using zEC12 causes
  failures in the valgrind tests since valgrind doesn't fully support
  this CPU yet.)

- z13 vector ABI is not yet supported.  To ensure compatible code
  generation, the -vector feature is passed to LLVM.  Note that this
  means that even when compiling for z13, no vector instructions
  will be used.  In the future, support for the vector ABI should be
  added (this will require common code support for different ABIs
  that need different data_layout strings on the same platform).

- Two test cases are (temporarily) ignored on s390x to allow passing
  the test suite.  The underlying issues still need to be fixed:
  * debuginfo/simd.rs fails because of incorrect debug information.
    This seems to be a LLVM bug (also seen with C code).
  * run-pass/union/union-basic.rs simply seems to be incorrect for
    all big-endian platforms.
Signed-off-by: NUlrich Weigand <ulrich.weigand@de.ibm.com>

When sizing DST, don't double-count nested struct prefixes.

When computing size of `struct P<T>(Q<T>)`, don't double-count prefix added by `Q`

Fix #36278. Fix #36294.

Rollup of 6 pull requests

- Successful merges: #35691, #36045, #36311, #36314, #36326, #36346
- Failed merges:

clean up `get_vtable`'s doc comment

Fixed typo in nomicon

doc: we got coercion going on here, so no need to be this explicit

Add doc example for `std::time::Instant::elapsed`.

None

rustdoc: Add missing item types to page titles

Most pages include the item type in the title such as "Struct std::vec::Vec". However it is missing from the pages for foreign functions, type definitions, macros, statics and constants. This adds them so for example, instead of a title of "std::u32::MAX" it is "Constant std::u32::MAX" to match the others.

[before](https://doc.rust-lang.org/nightly/std/u32/constant.MAX.html) [after](https://ollie27.github.io/rust_doc_test/std/u32/constant.MAX.html)
[before](https://doc.rust-lang.org/nightly/std/io/type.Result.html) [after](https://ollie27.github.io/rust_doc_test/std/io/type.Result.html)

Previous discussions: #34345, #35003

Update the wording for E0063. This will truncate the fields to 3.

Instead of listing every field it will now show missing `a`, `z`, `b`, and 1 other field
This is for #35218 as part of #35233

r? @jonathandturner

Handle `ReEmpty` for `impl Trait`

Closes #35668

r? @EddyB

add static_in_const feature gate

also updates tests and deletes the spurious .bk files I inadvertently added last time.

r? @nikomatsakis

This adds support for building the Rust compiler and standard
library for s390x-linux, allowing a full cross-bootstrap sequence
to complete.  This includes:

- Makefile/configure changes to allow native s390x builds
- Full Rust compiler support for the s390x C ABI
  (only the non-vector ABI is supported at this point)
- Port of the standard library to s390x
- Update the liblibc submodule to a version including s390x support
- Testsuite fixes to allow clean "make check" on s390x

Caveats:

- Resets base cpu to "z10" to bring support in sync with the default
  behaviour of other compilers on the platforms.  (Usually, upstream
  supports all older processors; a distribution build may then chose
  to require a more recent base version.)  (Also, using zEC12 causes
  failures in the valgrind tests since valgrind doesn't fully support
  this CPU yet.)

- z13 vector ABI is not yet supported.  To ensure compatible code
  generation, the -vector feature is passed to LLVM.  Note that this
  means that even when compiling for z13, no vector instructions
  will be used.  In the future, support for the vector ABI should be
  added (this will require common code support for different ABIs
  that need different data_layout strings on the same platform).

- Two test cases are (temporarily) ignored on s390x to allow passing
  the test suite.  The underlying issues still need to be fixed:
  * debuginfo/simd.rs fails because of incorrect debug information.
    This seems to be a LLVM bug (also seen with C code).
  * run-pass/union/union-basic.rs simply seems to be incorrect for
    all big-endian platforms.
Signed-off-by: NUlrich Weigand <ulrich.weigand@de.ibm.com>

adding a check to bootstrap script

and a check to the rust config script

refs #36207

first crack at making configure detect nodejs

Refactor `TyStruct`/`TyEnum`/`TyUnion` into `TyAdt`

r? @EddyB

save-analysis bits and pieces

Instead of listing every field it will now show missing `a`, `z`, `b`, and 1 other field

Fix argument to FIONBIO ioctl

The FIONBIO ioctl takes as argument a pointer to an integer, which
should be either 0 or 1 to indicate whether nonblocking mode is to
be switched off or on.  The type of the pointed-to variable is "int".

However, the set_nonblocking routine in libstd/sys/unix/net.rs passes
a pointer to a libc::c_ulong variable.  This doesn't matter on all
32-bit platforms and on all litte-endian platforms, but it will
break on big-endian 64-bit platforms.

Found while porting Rust to s390x (a big-endian 64-bit platform).
Signed-off-by: NUlrich Weigand <ulrich.weigand@de.ibm.com>

Follow target ABI sign-/zero-extension rules for enum types

While attempting to port Rust to s390x, I ran into an ABI violation
(that caused rust_eh_personality to be miscompiled, breaking unwinding).
The problem is that this function returns an enum type, which is
supposed to be sign-extended according to the s390x ABI.  However,
common code would ignore target sign-/zero-extension rules for any
types that do not satisfy is_integral(), which includes enums.

For the general case of Rust enum types, which map to structure types
with a discriminant, that seems correct.  However, in the special case
of simple enums that map directly to C enum types (i.e. LLVM integers),
this is incorrect; we must follow the target extension rules for those.
Signed-off-by: NUlrich Weigand <ulrich.weigand@de.ibm.com>

Due to missing noalias annotations for &mut T in general (issue #31681),
in larger programs extend_from_slice and extend_with_element may both
compile very poorly. What is observed is that the .set_len() calls are
not lifted out of the loop, even for `Vec<u8>`.

Use a local length variable for the Vec length instead, and use a scope
guard to write this value back to self.len when the scope ends or on
panic. Then the alias analysis is easy.

This affects extend_from_slice, extend_with_element, the vec![x; n]
macro, Write impls for Vec<u8>, BufWriter, etc (but may / may not
have triggered since inlining can be enough for the compiler to get it right).