removed incomplete comment

as written, I don't believe this comment was helpful; I think it's
better just to steer the reader toward a general understanding of
hygiene.
simplified test case
looks like a cut-n-paste error in unused code
adjust fold to fold over interpolated items/exprs/etc.

Closes #15221
comments only
auto merge of #15233 : jbclements/rust/match-var-hygiene-etc, r=cmr

This PR includes two big things and a bunch of little ones.

1) It enables hygiene for variables bound by 'match' expressions.
2) It fixes a bug discovered indirectly (#15221), wherein fold traversal failed to visit nonterminal nodes.
3) It fixes a small bug in the macro tutorial.

It also adds tests for the first two, and makes a bunch of small comment improvements and cleanup.
Add test for issue #12552

Closes #12552
auto merge of #15235 : Sawyer47/rust/issue-12552, r=huonw

Closes #12552
Add remark and an example about the bounds of `Vec::insert`
auto merge of #15214 : tbu-/rust/pr_doc_vecinsert, r=huonw
librustc: Match trait self types exactly.

This can break code that looked like:

    impl Foo for Box<Any> {
        fn f(&self) { ... }
    }

    let x: Box<Any + Send> = ...;
    x.f();

Change such code to:

    impl Foo for Box<Any> {
        fn f(&self) { ... }
    }

    let x: Box<Any> = ...;
    x.f();

That is, upcast before calling methods.

This is a conservative solution to #5781. A more proper treatment (see
the xfail'd `trait-contravariant-self.rs`) would take variance into
account. This change fixes the soundness hole.

Some library changes had to be made to make this work. In particular,
`Box<Any>` is no longer showable, and only `Box<Any+Send>` is showable.
Eventually, this restriction can be lifted; for now, it does not prove
too onerous, because `Any` is only used for propagating the result of
task failure.

This patch also adds a test for the variance inference work in #12828,
which accidentally landed as part of DST.

Closes #5781.

[breaking-change]
auto merge of #15191 : pcwalton/rust/variance-in-trait-matching, r=huonw

I believe that #5781 got fixed by the DST work. It duplicated the
variance inference work in #12828. Therefore, all that is left in #5781
is adding a test.

Closes #5781.

r? @huonw
Implementation of common traits for MaybeOwnedVector
Rename all raw pointers as necessary
auto merge of #15208 : alexcrichton/rust/snapshots, r=pcwalton

This change registers new snapshots, allowing `*T` to be removed from the language. This is a large breaking change, and it is recommended that if compiler errors are seen that any FFI calls are audited to determine whether they should be actually taking `*mut T`.
auto merge of #15210 : luqmana/rust/windoc, r=alexcrichton

Getting rust to build on windows can be a bit annoying in setting up all the toolchains and whatnot. The whole process is made much easier by using msys2 so let's document that prominently right on the README.
auto merge of #15241 : arjantop/rust/maybeownedvector-improvements, r=alexcrichton
librustc: Allow coercions through arrays.
Impl Rand for tuples of arity 11 and 12
rand: Small fix in parameter name

Documentation didn't match with parameter name.
Changes name of parameter in docs and function to 'amount'.