In our GitHub Actions setup macOS is too unreliable to gate on it, but
the other builders work fine. This commit splits the macOS builders into
a separate job (called auto-fallible), allowing us to gate on the auto
job without failing due to macOS spurious failures.

…trait_selection`.

This commit normalizes projections which contain opaque types (opaque types
are otherwise linted against, which is would have previously made the
test cases added in this commit fail).

Signed-off-by: David Wood <david@davidtw.co>

We now require that projection candidates are applicable with the
idenitity substs of the trait, rather than allowing predicates that are
only applicable for certain substs.

This was currently only happening due to eager normalization, which
isn't possible if there's specialization or bound variables.

Given `trait X { type U; }` the bound `<Self as X>::U` now lives
on the type, rather than the trait. This is feature gated on
`feature(generic_associated_types)` for now until more testing can
be done.

The also enabled type-generic associated types since we no longer
need "implies bounds".

This patch adds two methods to `Duration`. The first, `Duration::zero`,
provides a `const` constructor for getting an zero-length duration. This
is also what `Default` provides (this was clarified in the docs), though
`default` is not `const`.

The second, `Duration::is_zero`, returns true if a `Duration` spans no
time (i.e., because its components are all zero). Previously, the way to
do this was either to compare both `as_secs` and `subsec_nanos` to 0, to
compare against `Duration::new(0, 0)`, or to use the `u128` method
`as_nanos`, none of which were particularly elegant.

For some reason, the help message is now in a separate message, which
adds a lot of noise. I would like to try to get it back to one message.

That way the comma isn't highlighted as part of the option in the UI.

Weirdly, the comma removal suggestion shows up in the UI.

The UI isn't glitching anymore.

Try to suggest dereferences on trait selection failed

Fixes rust-lang#39029 Fixes rust-lang#62530
This PR consists of two parts:
1. Decouple `Autoderef` with `FnCtxt` and move `Autoderef` to `librustc_trait_selection`.
2. Try to suggest dereferences when trait selection failed.

The first is needed because:
1. For suggesting dereferences, the struct `Autoderef` should be used. But before this PR, it is placed in `librustc_typeck`, which depends on `librustc_trait_selection`. But trait selection error emitting happens in `librustc_trait_selection`, if we want to use `Autoderef` in it, dependency loop is inevitable. So I moved the `Autoderef` to `librustc_trait_selection`.
2. Before this PR, `FnCtxt` is coupled to `Autoderef`, and `FnCtxt` only exists in `librustc_typeck`. So decoupling is needed.

After this PR, we can get suggestion like this:
```
error[E0277]: the trait bound `&Baz: Happy` is not satisfied
  --> $DIR/trait-suggest-deferences-multiple.rs:34:9
   |
LL | fn foo<T>(_: T) where T: Happy {}
   |                          ----- required by this bound in `foo`
...
LL |     foo(&baz);
   |         ^^^^
   |         |
   |         the trait `Happy` is not implemented for `&Baz`
   |         help: consider adding dereference here: `&***baz`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
```

r? @estebank

…dation, r=nikomatsakis

Projection bound validation

During selection we use bounds declared on associated types (e.g. `type X: Copy`) to satisfy trait/projection bounds. This would be fine so long as those bounds are checked on any impls/trait objects. For simple cases they are because the bound `Self::X: Copy` gets normalized when we check the impl.

However, for default values with specialization and higher-ranked bounds from GATs or otherwise, we can't normalize when checking the impl, and so we use the bound from the trait to prove that the bound applies to the impl, which is clearly unsound.

This PR makes 2 fixes for this:

1. Requiring that the bounds on the trait apply to a projection type with the corresponding substs, so a bound `for<'a> <Self as X<'a>>::U: Copy` on the trait cannot be used to prove `<T as X<'_>>::U: Copy`.
2. Actually checking that the bounds that we still allow apply to generic/default associated types.

Opening for a crater run.

Closes rust-lang#68641
Closes rust-lang#68642
Closes rust-lang#68643
Closes rust-lang#68644
Closes rust-lang#68645
Closes rust-lang#68656

r? @ghost

…bertodt

core/time: Add Duration methods for zero

This patch adds two methods to `Duration`. The first, `Duration::zero`,
provides a `const` constructor for getting an zero-length duration. This
is also what `Default` provides (this was clarified in the docs), though
`default` is not `const`.

The second, `Duration::is_zero`, returns true if a `Duration` spans no
time (i.e., because its components are all zero). Previously, the way to
do this was either to compare both `as_secs` and `subsec_nanos` to 0, to
compare against `Duration::new(0, 0)`, or to use the `u128` method
`as_nanos`, none of which were particularly elegant.

…nieu

Allow multiple `asm!` options groups and report an error on duplicate options

Fixes rust-lang#73193

Cc @joshtriplett @Amanieu

- [x] Allow multiple options
- [x] Update existing test
- [x] Add new tests
- [x] Check for duplicate options
- [x] Add duplicate options tests
- [x] Finalize suggestion format for duplicate options error

…in-projections, r=estebank

lint: normalize projections using opaque types

Fixes rust-lang#73251.

This PR normalizes projections which use opaque types (opaque types are otherwise linted against, which is would have previously made the test cases added in this PR fail).

…=petrochenkov

Pre-compute `LocalDefId` <-> `HirId` mappings and remove `NodeId` <-> `HirId` conversion APIs

cc rust-lang#50928

I don't know who is exactly the best person to review this.

r? @petrochenkov

…oli-obk

Remove use of specialization from librustc_arena

This reworks the macro so that specialization, `transmute` and `#[marker]` are not used.

r? @oli-obk

Update bootstrap to rustc 1.45.0-beta.2 (1dc0f6d 2020-06-15)

Pulls in changes from rust-lang#73326.

Closes rust-lang#73286

…ark-Simulacrum

ci: allow gating GHA on everything but macOS

In our GitHub Actions setup macOS is too unreliable to gate on it, but the other builders work fine. This commit splits the macOS builders into a separate job (called `auto-fallible`), allowing us to gate on the auto job without failing due to macOS spurious failures.

cc rust-lang/rust-central-station#848
r? @Mark-Simulacrum