* Don't disambiguate if there are multiple impls for the same type.
* Disambiguate for impls of &Foo and &mut Foo.
* Don't try to disambiguate generic types.
rustdoc: print non-self arguments of bare functions and struct methods on their own line
This change alters the formatting rustdoc uses when it creates function and struct method documentation. For bare functions, each argument is printed on its own line. For struct methods, non-self arguments are printed on their own line. In both cases, no line breaks are introduced if there are no arguments, and for struct methods, no line breaks are introduced if there is only a single self argument. This should aid readability of long function signatures and allow for greater comprehension of these functions.
I've run rustdoc with these changes on my crate egg-mode and its set of dependencies and put the result [on my server](https://shiva.icesoldier.me/doc-custom/egg_mode/). Of note, here are a few shortcut links that highlight the changes:
* [Bare function with a long signature](https://shiva.icesoldier.me/doc-custom/egg_mode/place/fn.reverse_geocode.html)
* [Struct methods, with single self argument and with self and non-self arguments](https://shiva.icesoldier.me/doc-custom/egg_mode/tweet/struct.Timeline.html#method.reset)
* [Bare functions with no arguments](https://shiva.icesoldier.me/doc-custom/rand/fn.thread_rng.html) and [struct methods with no arguments](https://shiva.icesoldier.me/doc-custom/hyper/client/struct.Client.html#method.new) are left unchanged.
This PR consists of two commits: one for bare functions and one for struct methods.
* ignore signatures 80 characters or shorter
* otherwise, put arguments and return arrow on their own line, indented
to the opening parenthesis
in doing this, most of a plain-text output has been written for rustdoc,
accessible through "alternate" Display printing: "{:#}"
Currently methods from extern crates are sometimes added to the search
index when they shouldn't be or added with the original path rather than
the reexported path. This fixes that by making sure `cache().paths` only
contains local paths like the description for it states. It also fixes a
few minor issues with link rendering and redirect generation which would
point to local crate docs even if the docs for that crate hadn't been
generated.
Also a bug with methods implemented on traits which caused wrong paths and
so dead links in the search results has been fixed.
This is a spiritual succesor to #34268/8531d581, in which we replaced a
number of matches of None to the unit value with `if let` conditionals
where it was judged that this made for clearer/simpler code (as would be
recommended by Manishearth/rust-clippy's `single_match` lint). The same
rationale applies to matches of None to the empty block.
Remove ExplicitSelf from HIR
`self` argument is already kept in the argument list and can be retrieved from there if necessary, so there's no need for the duplication.
The same changes can be applied to AST, I'll make them in the next breaking batch.
The first commit also improves parsing of method declarations and fixes https://github.com/rust-lang/rust/issues/33413.
r? @eddyb
Especially in cases like the one in the test file, this can blow
up the docs big time if string constants in the code contain HTML.
But also other constants can contain special chars (e.g. `&` as an
operator in constant expressions).
