Document update and update_with_key in SmallIntMap.

Move update above for better docs progression.
Fix #15896

Fix ICE when there's an incorrect enum variant constructor in match arm.

Closes #15896.
librustc: Stop desugaring `for` expressions and translate them directly.

This makes edge cases in which the `Iterator` trait was not in scope
and/or `Option` or its variants were not in scope work properly.

This breaks code that looks like:

    struct MyStruct { ... }

    impl MyStruct {
        fn next(&mut self) -> Option<int> { ... }
    }

    for x in MyStruct { ... } { ... }

Change ad-hoc `next` methods like the above to implementations of the
`Iterator` trait. For example:

    impl Iterator<int> for MyStruct {
        fn next(&mut self) -> Option<int> { ... }
    }

Closes #15392.

[breaking-change]
Remove obsolete Japanese translation for a while.

The translation is based on an early version of tutorial.md, thus most
of entries have been marked as fuzzy and actually they are incorrect.
Now tutorial.md is planed to be replaced with guide.md, so I'd suggest
removing translation files for a while.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
librustc: Make references to functions not have static lifetime.

This breaks code like:

    struct A<'a> {
        func: &'a fn() -> Option<int>
    }

    fn foo() -> Option<int> { ... }

    fn create() -> A<'static> {
        A {
            func: &foo
        }
    }

Change this code to not take functions by reference. For example:

    struct A {
        func: extern "Rust" fn() -> Option<int>
    }

    fn foo() -> Option<int> { ... }

    fn create() -> A {
        A {
            func: foo
        }
    }

Closes #13595.

[breaking-change]
librustc: Check built-in trait bounds on implementations when direct
method calls are involved.

This breaks code like:

    impl<T:Copy> Foo for T { ... }

    fn take_param<T:Foo>(foo: &T) { ... }

    fn main() {
        let x = box 3i; // note no `Copy` bound
        take_param(&x);
    }

Change this code to not contain a type error. For example:

    impl<T:Copy> Foo for T { ... }

    fn take_param<T:Foo>(foo: &T) { ... }

    fn main() {
        let x = 3i; // satisfies `Copy` bound
        take_param(&x);
    }

Closes #15860.

[breaking-change]
Add noalias to safe shared reference parameters

This add the LLVM noalias attribute to parameters of a
shared reference type (&) which have a safe interior.
rustc: Compare paths with --extern, not bytes

The right hand side of the comparison in these checks are values of type
Option<&Path> which are normalized versions of the left-hand side, so they're
not guaranteed to be byte-for-byte equivalent even though they're the same path.

For this reasons, the command line arguments are promoted to paths for
comparison of equality.

This fixes a bug on windows where if a library was specified with --extern it
would then be picked up twice because it was not considered to have been
previously registered.
Fix display of `-NaN%` in borrock stats caused by div by zero
Add methods for obtaining iterators over the keys and values of a TreeMap
Add methods for obtaining iterators over the keys and values of a SmallIntMap
Add methods for obtaining iterators over the keys and values of a TrieMap
Fix assert message
Fill in example code for HashMap.

Add an example showing how to use the map with a custom type. Fill in
examples for methods in the hashmap file without ones.

Also move pop_equiv next to related public methods, to not create a
duplicate trait implementation in the docs.
Remove explicit rust code specifier. Unhide use HashMap.
Cleanup HashMap documentation.

Link to mentioned methods. Use `# Failure` tags to describe failure.
Make `pop_equiv`, `find_equiv` and `get_copy` standalone.
Guide Redux: Pointers
Emit lifetime end markers in unwinding codepaths

Currently we don't emit lifetime end markers when translating the
unwinding code. I omitted that when I added the support for lifetime
intrinsics, because I initially made the mistake of just returning true
in clean_on_unwind(). That caused almost all calls to be translated as
invokes, leading to quite awful results.

To correctly emit the lifetime end markers, we must differentiate
between cleanup that requires unwinding and such cleanup that just wants
to emit code during unwinding.
rustdoc: Add a --target flag

Closes #13893
rustdoc: Hide impls for #[doc(hidden)] traits

Closes #14585