rustbuild: Skip the build_helper crate in tests

I've been noticing some spurious recompiles of the final stage on Travis lately
and in debugging them I found a case where we were a little to eager to update
a stamp file due to the build_helper library being introduced during the testing
phase.

Part of the rustbuild system detects when libstd is recompiled and automatically
cleans out future directories to ensure that dirtyness propagation works. To do
this rustbuild doesn't know the artifact name of the standard library so it just
probes everything in the target directory, looking to see if anything changed.

The problem here happened where:

* First, rustbuild would compile everything (a normal build)
* Next, rustbuild would run all tests
* During testing, the libbuild_helper library was introduced into the target
  directory, making it look like a change happened because a file is newer
  than the newest was before
* Detecting a change, the next compilation would then cause rustbuild to clean
  out old artifacts and recompile everything again.

This commit fixes this problem by correcting rustbuild to just not test the
build_helper crate at all. This crate doesn't have any unit tests, nor is it
intended to. That way the target directories should stay the same throughout
testing after a previous build.

Add try_wait to Redox process

This implements Process::try_wait on Redox

Use multiline Diagnostic for "relevant impl" list

Provide the following output:

```
error[E0277]: the trait bound `Bar: Foo<usize>` is not satisfied
  --> $DIR/issue-21659-show-relevant-trait-impls-2.rs:38:8
   |
38 |     f1.foo(1usize);
   |        ^^^ the trait `Foo<usize>` is not implemented for `Bar`
   |
   = help: the following implementations were found:
             <Bar as Foo<i8>>
             <Bar as Foo<i16>>
             <Bar as Foo<i32>>
             <Bar as Foo<u8>>
           and 2 others

error: aborting due to previous error
```

instead of

```
error[E0277]: the trait bound `Bar: Foo<usize>` is not satisfied
  --> $DIR/issue-21659-show-relevant-trait-impls-2.rs:38:8
   |
38 |     f1.foo(1usize);
   |        ^^^ the trait `Foo<usize>` is not implemented for `Bar`
   |
   = help: the following implementations were found:
   = help:   <Bar as Foo<i8>>
   = help:   <Bar as Foo<i16>>
   = help:   <Bar as Foo<i32>>
   = help:   <Bar as Foo<u8>>
   = help: and 2 others

error: aborting due to previous error
```

rustbuild: Actually don't build stage0 target rustc

This was attempted in #38853 but erroneously forgot one more case of where the
compiler was compiled. This commit fixes that up and adds a test to ensure this
doesn't sneak back in.

incr.comp.: Add some caching to Predecessors construction.

This speeds up the "serialize dep graph" pass for libsyntax from 45 secs to 15 secs on my machine. Still far from ideal, but things will get better when we change the metadata hashing strategy.

The `CACHING_THRESHOLD` value of 60 has been arrived at experimentally. It seemed to give the best speedup.

r? @nikomatsakis

Fix two const-eval issues related to i128 negation

First issue here was the fact that we’d only allow negating integers in i64 range in case the
integer was not infered yes. While this is not the direct cause of the issue, its still good to fix
it.

The real issue here is the code handling specifically the `min_value` literals. While I128_OVERFLOW
has the expected value (0x8000_..._0000), match using this value as a pattern is handled
incorrectly by the stage1 compiler (it seems to be handled correctly, by the stage2 compiler). So
what we do here is extract this pattern into an explicit `==` until the next snapshot.

Fixes #38987

expect_err for Result.

This adds an `expect_err` method to `Result`. Considering how `unwrap_err` already exists, this seems to make sense. Inconsistency noted in Manishearth/rust-clippy#1435.

save-analysis: handle paths in type/trait context more correctly

TBH, this is still not perfect, witness the FIXME, but it is an improvement. In particular it means we get information about trait references in impls.

trans: Treat generics like regular functions, not like #[inline] function, during CGU partitioning

This PR makes generics be treated just like regular functions during CGU partitioning:

+ the function instantiation is placed in a codegen unit based on the function's DefPath,
+ unless it is marked with `#[inline]`  -- which causes a private copy of the function to be placed in every referencing codegen unit.

This has the following effects:
+ Multi codegen unit builds will become faster because code for generic functions is duplicated less.
+ Multi codegen unit builds might have lower runtime performance, since generics are not available for inlining automatically any more.
+ Single codegen unit builds are not affected one way or the other.

This partitioning scheme is particularly good for incremental compilation as it drastically reduces the number of false positives during codegen unit invalidation.

I'd love to have a benchmark suite for estimating the effect on runtime performance for changes like this one.

r? @nikomatsakis

cc @rust-lang/compiler

Fix is_absolute on Redox

Due to not using prefixes on Redox, yet, it must be added as an exception to Path::is_absolute.

resolve: Levenshtein-based suggestions for non-import paths

This patch addresses both items from https://github.com/rust-lang/rust/issues/30197#issuecomment-264846000 and therefore implements the largest part of https://github.com/rust-lang/rust/issues/30197.

r? @jseyfried

Make tidy check for lang gate tests

Add gate tests to the checks that tidy performs. Excerpt from the commit message of the main commit:

    Require compile-fail tests for new lang features

    Its non trivial to test lang feature gates, and people
    forget to add such tests. So we extend the features lint
    of the tidy tool to ensure that all new lang features
    contain a new compile-fail test.

    Of course, one could drop this requirement and just
    grep all tests in run-pass for #![feature(abc)] and
    then run this test again, removing the mention,
    requiring that it fails.

    But this only tests for the existence of a compilation
    failure. Manual tests ensure that also the correct lines
    spawn the error, and also test the actual error message.

    For library features, it makes no sense to require such
    a test, as here code is used that is generic for all
    library features.

The tidy lint extension now checks the compile-fail test suite for occurences of "gate-test-X" where X is a feature. Alternatively, it also accepts file names with the form "feature-gate-X.rs". If a lang feature is found that has no such check, we emit a tidy error.

I've applied the markings to all tests I could find in the test suite. I left a small (20 elements) whitelist of features that right now have no gate test, or where I couldn't find one. Once this PR gets merged, I'd like to close issue #22820 and open a new one on suggestion of @nikomatsakis to track the removal of all elements from that whitelist (already have a draft). Writing such a small test can be a good opportunity for a first contribution, so I won't touch it (let others have the fun xD).

cc @brson , @pnkfelix (they both discussed about this in the issue linked above).

travis: Attempt to debug OSX linker segfaults

This commit attempts to debug the segfaults that we've been seeing on OSX on
Travis. I have no idea what's going on here mostly, but let's try to look at
core dumps and get backtraces to see what's going on. This commit itself is
mostly a complete shot in the dark, I'm not sure if this even works...

cc #38878

Simplify type_is_immediate and type_is_fat_ptr

r? @EddyB

Rollup of 10 pull requests

- Successful merges: #38362, #38636, #38877, #38946, #38965, #38986, #38994, #38995, #39024, #39027
- Failed merges:

LLVM usually prefers using memcpys over direct loads/store of first
class aggregates. The check in type_is_immediate to mark certain small
structs was originally part of the code to handle such immediates in
function arguments, and it had a counterpart in load_ty/store_ty to
actually convert small aggregates to integers.

But since then, the ABI handling has been refactored and takes care of
converting small aggregates to integers. During that refactoring, the
code to handle small aggregates in load_ty/store_ty has been removed,
and so we accidentally started using loads/stores on FCA values.

Since type_is_immediate() is no longer responsible for ABI-related
conversions, and using a memcpy even for small aggregates is usually
better than performing a FCA load/store, we can remove that code part
and only handle simple types as immediates there.

This integrates PR #38906 onto this branch.

Fixes #38906.

I've been noticing some spurious recompiles of the final stage on Travis lately
and in debugging them I found a case where we were a little to eager to update
a stamp file due to the build_helper library being introduced during the testing
phase.

Part of the rustbuild system detects when libstd is recompiled and automatically
cleans out future directories to ensure that dirtyness propagation works. To do
this rustbuild doesn't know the artifact name of the standard library so it just
probes everything in the target directory, looking to see if anything changed.

The problem here happened where:

* First, rustbuild would compile everything (a normal build)
* Next, rustbuild would run all tests
* During testing, the libbuild_helper library was introduced into the target
  directory, making it look like a change happened because a file is newer
  than the newest was before
* Detecting a change, the next compilation would then cause rustbuild to clean
  out old artifacts and recompile everything again.

This commit fixes this problem by correcting rustbuild to just not test the
build_helper crate at all. This crate doesn't have any unit tests, nor is it
intended to. That way the target directories should stay the same throughout
testing after a previous build.

Provide the following output:

```
error[E0277]: the trait bound `Bar: Foo<usize>` is not satisfied
  --> $DIR/issue-21659-show-relevant-trait-impls-2.rs:38:8
   |
38 |     f1.foo(1usize);
   |        ^^^ the trait `Foo<usize>` is not implemented for `Bar`
   |
   = help: the following implementations were found:
             <Bar as Foo<i8>>
             <Bar as Foo<i16>>
             <Bar as Foo<i32>>
             <Bar as Foo<u8>>
           and 2 others

error: aborting due to previous error
```

instead of

```
error[E0277]: the trait bound `Bar: Foo<usize>` is not satisfied
  --> $DIR/issue-21659-show-relevant-trait-impls-2.rs:38:8
   |
38 |     f1.foo(1usize);
   |        ^^^ the trait `Foo<usize>` is not implemented for `Bar`
   |
   = help: the following implementations were found:
   = help:   <Bar as Foo<i8>>
   = help:   <Bar as Foo<i16>>
   = help:   <Bar as Foo<i32>>
   = help:   <Bar as Foo<u8>>
   = help: and 2 others

error: aborting due to previous error
```

Remove strictly-unnecessary flags for docker

cc #39035

In addition to `--tty` I've removed `--interactive` as I don't think there's any reason for it to be there (it only hooks up stdin, which shouldn't be used anyway).

If this looks like it's working over a few days then I'll also alter the libc scripts.

r? @alexcrichton

resolve: Do not use "resolve"/"resolution" in error messages

Use less jargon-y wording instead.
`cannot find <struct> <S> in <this scope>` and `cannot find <struct> <S> in <module a::b>` are used for base messages (this also harmonizes nicely with "you can import it into scope" suggestions) and `not found in <this scope>` and `not found in <a::b>` are used for short labels in fall-back case.
I tweaked some other diagnostics to avoid using "resolve" (see, e.g., `librustc_resolve/macros.rs`), but haven't touched messages for imports.

Closes https://github.com/rust-lang/rust/issues/38750
r? @nrc

[libcollections] [doc] Fix typo in documentation

Replace two instances of `an raw` with `a raw` in documentation blocks.

Change `to_owned` to `to_string` in docs

We should teach conversion from `str` to `String` using `to_string` rather than the legacy `to_owned`.

Fix docs for min/max algorithms

I thought at first "what did they think about when stabilizing this!?", but it turned out it's just wrong docs. Phew.

r? @steveklabnik

Test:
```
use std::cmp::Ordering;

struct S(u8, u8);

impl PartialEq for S {
    fn eq(&self, other: &Self) -> bool {
        self.0 == other.0
    }
}
impl PartialOrd for S {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.0.cmp(&other.0))
    }
}
impl Ord for S {
    fn cmp(&self, other: &Self) -> Ordering {
        self.0.cmp(&other.0)
    }
}

fn main() {
    let arr = [S(0, 1), S(0, 2)];
    println!("min {:?}", arr.iter().min());
    println!("min_by {:?}", arr.iter().min_by(|x, y| x.0.cmp(&y.0)));
    println!("min_by_key {:?}", arr.iter().min_by_key(|x| x.0));
    println!("max {:?}", arr.iter().max());
    println!("max_by {:?}", arr.iter().max_by(|x, y| x.0.cmp(&y.0)));
    println!("max_by_key {:?}", arr.iter().max_by_key(|x| x.0));
}
```
Output:
```
rustc 1.15.0-beta.3 (a035041b 2017-01-07)
min Some(S(0, 1))
min_by Some(S(0, 1))
min_by_key Some(S(0, 1))
max Some(S(0, 2))
max_by Some(S(0, 2))
max_by_key Some(S(0, 2))
```

Fix some typos in Nomicon

I waited a bit before creating this PR in case I find more typos – I didn't.

I've read `CONTRIBUTING.md` but didn't `make check`, and `make doc` takes incredibly long. (Among other things, `make doc` builds llvm from scratch.  Not sure if that's intentional.)

std/net/udp: Improve set_nonblocking test

While writing a separate change, I noticed the current test for `UdpSocket::set_nonblocking()` is fairly ineffective.

This fixes the test so that it validates that a correct error is returned on calls to `recv()` when no data is available.

Add missing doc examples for Mutex

r? @frewsxcv

Add missing links and examples for path modules and structs

r? @frewsxcv

libcompiler_builtins: Don't build emutls.c

Rather than improving the check, let's ditch emutls.c entirely.

Clarify Extend behaviour wrt existing keys

This seems to be consistent with all the Extend implementations I found, and isn't documented anywhere else afaik.

Instant doc

r? @frewsxcv

Implement Display for char Escape*, To*case.

See: rust-lang/rfcs#1848.

A good example of where this is useful would be in the example `print!("{}", 'ß'.to_uppercase())`.

Not sure if this requires a formal RFC, but I decided to write the code for it anyway regardless.

travis: Start uploading artifacts on commits

This commit starts adding the infrastructure for uploading release artifacts
from AppVeyor/Travis on each commit. The idea is that eventually we'll upload a
full release to AppVeyor/Travis in accordance with plans [outlined earlier].

Right now this configures Travis/Appveyor to upload all tarballs in the `dist`
directory, and various images are updated to actually produce tarballs in these
directories. These are nowhere near ready to be actual release artifacts, but
this should allow us to play around with it and test it out. Once this commit
lands we should start seeing artifacts uploaded on each commit.

[outlined earlier]: https://internals.rust-lang.org/t/rust-ci-release-infrastructure-changes/4489

This was attempted in #38853 but erroneously forgot one more case of where the
compiler was compiled. This commit fixes that up and adds a test to ensure this
doesn't sneak back in.