Improve code reuse between trans/_match.rs and check_match.rs

The specialization logic for patterns is really the same in both
exhaustiveness/reachability checking and codegen.
auto merge of #15078 : jakub-/rust/pattern-matching-refactor-vol-2, r=pnkfelix

I believe there's more commonality to be found there but maybe small steps are better. I'm also in the process of documenting what I can, I will see if I can add it to this PR.

It also seems to me that ideally some of this stuff (especially the pattern sanity check) could live as a separate compiler-agnostic module but I understand this may not be the right time (if not the worst) to start the process of modularising rustc.
auto merge of #15199 : michaelwoerister/rust/cross-crate-stability, r=luqmana

So far, type names generated for debuginfo where a bit sketchy. It was not clearly defined when a name should be fully qualified and when not, if region parameters should be shown or not, and other things like that.
This commit makes the debuginfo module responsible for creating type names instead of using `ppaux::ty_to_str()` and brings type names (as they show up in the DWARF information) in line with GCC and Clang:

* The name of the type being described is unqualified. It's path is defined by its position in the namespace hierarchy.
* Type arguments are always fully qualified, no matter if they would actually be in scope at the type definition location.

Care is also taken to make type names consistent across crate boundaries. That is, the code now tries make the type name the same, regardless if the type is in the local crate or reconstructed from metadata. Otherwise LLVM will complain about violating the one-definition-rule when using link-time-optimization.

This commit also removes all source location information from type descriptions because these cannot be reconstructed for types instantiated from metadata. Again, with LTO enabled, this can lead to two versions of the debuginfo type description, one with and one without source location information, which then triggers the LLVM ODR assertion.
Fortunately, source location information about types is rarely used, so this has little impact. Once source location information is preserved in metadata (#1972) it can also be re-enabled for type descriptions.

`RUSTFLAGS=-g make check` no works again for me locally, including the LTO test cases (note that I've taken care of #15156 by reverting the change in LLVM that @luqmana identified as the culprit for that issue).
auto merge of #15331 : Derecho/rust/master, r=alexcrichton

One of the examples in the docs on adding documentation to rust code has an error that will cause the function to run endlessly rather than return the desired result, should someone actually implement this for some reason. While the error does not hinder the explanation of documenting code, it does look better if it is corrected.
auto merge of #15338 : pfalabella/rust/rational-impl-2, r=alexcrichton

Tried squashing commits for https://github.com/rust-lang/rust/pull/15329, failed spectacularly.
This is a fresh PR for the same change.

@alexcrichton?
Rename ctime to asctime and add *proper* ctime.

In C, `ctime(t)` is equivalent to `asctime(localtime(t))`, so the result
should depend on the local timezone. Current `ctime` is compatible with
`asctime` in C, not `ctime`.

This commit renames `ctime` to `asctime` and adds `ctime` which converts
the time to the local timezone before formatting it.

This commit also fixes the documentation of them. Current documentation
of `ctime` says it returns "a string of the current time." However, it
actually returns a string of the time represented as `self`, not the
time when it is called.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
rustc: Fix a call to with_path in trans_unboxing_shim

This was causing lots of ICEs in cargo. I sadly wasn't ever able to reduce the
test case down, but I presume that's because it has to do with node id
collisions which are pretty difficult to turn up...
auto merge of #15370 : alexcrichton/rust/fix-cargo, r=pnkfelix

This was causing lots of ICEs in cargo. I sadly wasn't ever able to reduce the
test case down, but I presume that's because it has to do with node id
collisions which are pretty difficult to turn up...
Guide: if
Add os::join_paths, make setenv non-utf8 capable

This commit changes `os` in three ways:

* It adds a `join_paths` function that is the converse to `split_paths`,
  easing manipulation of the `PATH` environment variable according to
  platform conventions.

* **Breaking change**: It changes `split_paths` to no longer drop empty paths, since they are
  meaningful to some shells (where they are synonymous with the current
  working directory).

* It changes `setenv` to take a `BytesContainer` rather than a `&str`
  value, since environment variables may have non-utf8 values on some
  platforms. Since `&str` is a `BytesContainer`, this is *not* a
  breaking change.

Along the way, it also refactors the `split_paths` function so that
`cfg` switches are applied internally (and the function header is given
only once). This fixes a bug: the doc comment had an example for only
one platform.

[breaking-change]
Guide: functions

Just a few words about functions and defining them.
Rationals that have a 1 denom should print like ints
Simplify PatIdent to contain an Ident rather than a Path

Rationale: for what appear to be historical reasons only, the PatIdent contains
a Path rather than an Ident.  This means that there are many places in the code
where an ident is artificially promoted to a path, and---much more problematically---
a bunch of elements from a path are simply thrown away, which seems like an invitation
to some really nasty bugs.

This commit replaces the Path in a PatIdent with a SpannedIdent, which just contains an ident
and a span.
Guide: add mutable binding section

Fixes #15334.
Fix ICE with nested macro_rules!-style macros

Fixes #10536.
remove duplicated slash in install script path
correct a few spelling mistakes in the tutorial
librustc: Have the kind checker check sub-bounds in trait casts.

This can break code that looked like:

    struct S<T> {
        val: T,
    }
    trait Gettable<T> {
        ...
    }
    impl<T: Copy> Gettable<T> for S<T> {
        ...
    }
    let t: Box<S<String>> = box S {
        val: "one".to_string(),
    };
    let a = t as Box<Gettable<String>>;
    //                        ^ note no `Copy` bound

Change this code to:

    impl<T> Gettable<T> for S<T> {
    //   ^ remove `Copy` bound
        ...
    }

Closes #14061.

[breaking-change]
Fix spelling errors.
Rename set_broadast() to set_broadcast().