Fix docs formatting for `thir::pattern::_match`

They were being rendered all on one line.

Fixes a word typo in librustdoc

Fixes a word typo in librustdoc

Fix persisted doctests on Windows / when using workspaces

When using the unstable `--persist-doctests` option,
Windows path separators were not escaped properly. Also when running
the command in a workspace, crate files can overwrite each other.

Before: `src\lib_rs_1_0\rust_out`
After: `\crate_a_src_lib_rs_1_0\rust_out`, `\crate_b_src_lib_rs_1_0\rust_out`

Clean up rustdoc tests by removing unnecessary features

r? ``@jyn514``

Fix typos

Upgrades the coverage map to Version 4

Changes the coverage map injected into binaries compiled with
`-Zinstrument-coverage` to LLVM Coverage Mapping Format, Version 4 (from
Version 3). Note, binaries compiled with this version will require LLVM
tools from at least LLVM Version 11.

r? ``@wesleywiser``

Lower patterns before using the bound variable

So as to avoid having to lower patterns twice.

Move lev_distance to rustc_ast, make non-generic

rustc_ast currently has a few dependencies on rustc_lexer. Ideally, an AST
would not have any dependency its lexer, for minimizing
design-time dependencies. Breaking this dependency would also have practical
benefits, since modifying rustc_lexer would not trigger a rebuild of rustc_ast.

This commit does not remove the rustc_ast --> rustc_lexer dependency,
but it does remove one of the sources of this dependency, which is the
code that handles fuzzy matching between symbol names for making suggestions
in diagnostics. Since that code depends only on Symbol, it is easy to move
it to rustc_span. It might even be best to move it to a separate crate,
since other tools such as Cargo use the same algorithm, and have simply
contain a duplicate of the code.

This changes the signature of find_best_match_for_name so that it is no
longer generic over its input. I checked the optimized binaries, and this
function was duplicated for nearly every call site, because most call sites
used short-lived iterator chains, generic over Map and such. But there's
no good reason for a function like this to be generic, since all it does
is immediately convert the generic input (the Iterator impl) to a concrete
Vec<Symbol>. This has all of the costs of generics (duplicated method bodies)
with no benefit.

Changing find_best_match_for_name to be non-generic removed about 10KB of
code from the optimized binary. I know it's a drop in the bucket, but we have
to start reducing binary size, and beginning to tame over-use of generics
is part of that.

suggest turbofish syntax for uninferred const arguments

When not providing a const generic value, and it can not be inferred, the following suggestion is suggested:
![image](https://user-images.githubusercontent.com/39732259/95616180-af127b80-0a69-11eb-8877-551c815f9627.png)

Resolves #76737

r? ``@varkor``

Mirror centos vault to S3

The angle brackets were confusing my IDE and I thought they were unnecessary. I was wrong.

A list was being rendered all on one line and there were other
formatting issues as well.

Validate use of parameters in naked functions

* Reject use of parameters inside naked function body.
* Reject use of patterns inside function parameters, to emphasize role
  of parameters a signature declaration (mirroring existing behaviour
  for function declarations) and avoid generating code introducing
  specified bindings.

Closes issues below by considering input to be ill-formed.

Closes #75922.
Closes #77848.
Closes #79350.

Always invoke statement attributes on the statement itself

This is preparation for PR #78296, which will require us to handle
statement items in addition to normal items.

Only create `OnDiskCache` in incremental compilation mode

This lets us skip doing useless work when we're not in incremental
compilation mode.

When using the unstable `--persist-doctests` option,
Windows path separators were not escaped properly. Also when running
the command in a workspace, crate files can overwrite each other.

Before: `src\lib_rs_1_0\rust_out`
After: `\crate_a_src_lib_rs_1_0\rust_out`, `\crate_b_src_lib_rs_1_0\rust_out`

Add `summary_opts()` for Markdown summary rendering options

We have a similar function `opts()` that is for rendering the main body
of the documentation, but until now we just constructed the options for
rendering summaries on the fly. This is a problem if/when we change the
enabled options since the different places can get out-of-sync.

TRACK '-Z polonius' flag

Fixes #79316.

r? `@jonas-schievink`

Validate that `#[naked]` is applied to a function definition

Rename `optin_builtin_traits` to `auto_traits`

They were originally called "opt-in, built-in traits" (OIBITs), but
people realized that the name was too confusing and a mouthful, and so
they were renamed to just "auto traits". The feature flag's name wasn't
updated, though, so that's what this PR does.

There are some other spots in the compiler that still refer to OIBITs,
but I don't think changing those now is worth it since they are internal
and not particularly relevant to this PR.

Also see <https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/opt-in.2C.20built-in.20traits.20(auto.20traits).20feature.20name>.

r? `@oli-obk` (feel free to re-assign if you're not the right reviewer for this)

Proposal to add Peekable::peek_mut

A "peekable" iterator has a `peek()`-method which provides an immutable reference to the next item. We currently do not have a method to modify that item, which we could easily add via a `peek_mut()`. See the test for a use-case (alike to my original use case), where a "pristine" iterator is passed on after modifying its state via `peek_mut()`.

If there is interest in this, I can expand on the tests and docs.

We have a similar function `opts()` that is for rendering the main body
of the documentation, but until now we just constructed the options for
rendering summaries on the fly. This is a problem if/when we change the
enabled options since the different places can get out-of-sync.

Document unsafety in core::slice::memchr

Contributes to #66219

Note sure if that's good enough, especially for the `align_to` call.
The docs only mention transmuting and I don't think that everything related to reference lifetimes and state validity mentioned in the [nomicon](https://doc.rust-lang.org/nomicon/transmutes.html) are relevant here.

Co-authored-by: NWesley Wiser <wwiser@gmail.com>

Goodbye, OIBIT!

rustc_ast currently has a few dependencies on rustc_lexer. Ideally, an AST
would not have any dependency its lexer, for minimizing unnecessarily
design-time dependencies. Breaking this dependency would also have practical
benefits, since modifying rustc_lexer would not trigger a rebuild of rustc_ast.

This commit does not remove the rustc_ast --> rustc_lexer dependency,
but it does remove one of the sources of this dependency, which is the
code that handles fuzzy matching between symbol names for making suggestions
in diagnostics. Since that code depends only on Symbol, it is easy to move
it to rustc_span. It might even be best to move it to a separate crate,
since other tools such as Cargo use the same algorithm, and have simply
contain a duplicate of the code.

This changes the signature of find_best_match_for_name so that it is no
longer generic over its input. I checked the optimized binaries, and this
function was duplicated at nearly every call site, because most call sites
used short-lived iterator chains, generic over Map and such. But there's
no good reason for a function like this to be generic, since all it does
is immediately convert the generic input (the Iterator impl) to a concrete
Vec<Symbol>. This has all of the costs of generics (duplicated method bodies)
with no benefit.

Changing find_best_match_for_name to be non-generic removed about 10KB of
code from the optimized binary. I know it's a drop in the bucket, but we have
to start reducing binary size, and beginning to tame over-use of generics
is part of that.

* Reject use of parameters inside naked function body.
* Reject use of patterns inside function parameters, to emphasize role
  of parameters a signature declaration (mirroring existing behaviour
  for function declarations) and avoid generating code introducing
  specified bindings.

driver: Only output ANSI logging if connected to a terminal

Fixes #78435.

See #78435 for more.

Cc `@RalfJung` `@oli-obk`

* `rustc` should now compile under LLVM 9 or 10
* Compiler generates an error if `-Z instrument-coverage` is specified
  but LLVM version is less than 11
* Coverage tests that require `-Z instrument-coverage` and run codegen
  should be skipped if LLVM version is less than 11

This is preparation for PR #78296, which will require us to handle
statement items in addition to normal items.