Allow inference regions when relating consts

As first noticed by @EddyB, `super_relate_consts` doesn't need to check for inference vars since `eval` does it already (and handles lifetimes correctly by erasing them).

Fixes #73050

r? @oli-obk

expand: More precise locations for expansion-time lints

First commit: a macro expansion doesn't have a `NodeId` associated with it, but it has a parent `DefId` which we can use for linting.
The observable effect is that lints associated with macro expansions can now be `allow`ed at finer-grained level than whole crate.

Second commit: each macro definition has a `NodeId` which we can use for linting, unless that macro definition was decoded from other crate.

Migrate to numeric associated consts

The deprecation PR is #72885

cc #68490
cc rust-lang/rfcs#2700

Update cargo

2 commits in 1ec223effbbbf9fddd3453cdcae3a96a967608eb..79c769c3d7b4c2cf6a93781575b7f592ef974255
2020-06-09 20:03:14 +0000 to 2020-06-11 22:13:37 +0000
- Fix failure with missing readme. (rust-lang/cargo#8353)
- Some LTO fixes. (rust-lang/cargo#8349)

Enable AVR as a Tier 3 target upstream

Tracking issue: #44052.

Things intentionally left out of the initial upstream:

* The `target_cpu` flag

I have made the cleanup suggestions by @jplatte and @jplatte in https://github.com/avr-rust/rust/commit/043550d9db0582add42e5837f636f61acb26b915.

Anybody feel free to give the branch a test and see how it fares, or make suggestions on the code patch itself.

Rollup of 7 pull requests

Successful merges:

 - #73033 (Fix #[thread_local] statics as asm! sym operands)
 - #73036 (std: Enable atomic.fence emission on wasm32)
 - #73163 (Add long error explanation for E0724)
 - #73187 (Remove missed `cfg(bootstrap)`)
 - #73195 (Provide suggestion to convert numeric op LHS rather than unwrapping RHS)
 - #73247 (Add various Zulip notifications for prioritization)
 - #73254 (Add comment about LocalDefId -> DefId)

Failed merges:

r? @ghost

Add comment about LocalDefId -> DefId

Now there are instructions on how to convert back and forth on both
structs, not just one.

See also https://github.com/rust-lang/rust/pull/73076

r? @lcnr

Add various Zulip notifications for prioritization

Adapts `triagebot.toml` for rust-lang/triagebot#616 and adds various Zulip notifications for the Prioritization WG workflow.
We should also add indications about the procedure for handling those events, cc @rust-lang/wg-prioritization.

r? @spastorino
This should be merged as soon as possible after rust-lang/triagebot#616 is merged, cc @Mark-Simulacrum

Provide suggestion to convert numeric op LHS rather than unwrapping RHS

Given a code

```rust
fn foo(x: u8, y: u32) -> bool {
    x > y
}
fn main() {}
```

it could be more helpful to provide a suggestion to do "u32::from(x)"
rather than "y.try_into().unwrap()", since the latter may panic.

We do this by passing the LHS of a binary expression up the stack into
the coercion checker.

Closes #73145

Remove missed `cfg(bootstrap)`

Add long error explanation for E0724

Add long explanation for the E0724 error code
Part of #61137

std: Enable atomic.fence emission on wasm32

This commit removes the `#[cfg]` guards in `atomic::fence` on wasm
targets. Since these guards were originally added the upstream wasm
specification for threads gained an `atomic.fence` instruction, so LLVM
no longer panics on these intrinsics.

Although there aren't a ton of tests in-repo for this right now I've
tested locally and all of these fences generate `atomic.fence`
instructions in wasm.

Closes #65687
Closes #72997

Fix #[thread_local] statics as asm! sym operands

The `asm!` RFC specifies that `#[thread_local]` statics may be used as `sym` operands for inline assembly.

This also fixes a regression in the handling of `#[thread_local]` during monomorphization which caused link-time errors with multiple codegen units, most likely introduced by #71192.

r? @oli-obk

Now there are instructions on how to convert back and forth on both
structs, not just one.

Rollup of 7 pull requests

Successful merges:

 - #72180 (remove extra space from crate-level doctest names)
 - #73012 (Show `SyntaxContext` in formatted `Span` debug output)
 - #73097 (Try_run must only be used if toolstate is populated)
 - #73169 (Handle assembler warnings properly)
 - #73182 (Track span of function in method calls, and use this in #[track_caller])
 - #73207 (Clean up E0648 explanation)
 - #73230 (Suggest including unused asm arguments in a comment to avoid error)

Failed merges:

r? @ghost

Minor refactoring

Minor refactoring

Update src/librustc_error_codes/error_codes/E0724.md
Co-authored-by: NDavid Wood <Q0KPU0H1YOEPHRY1R2SN5B5RL@david.davidtw.co>

Update src/librustc_error_codes/error_codes/E0724.md
Co-authored-by: NDavid Wood <Q0KPU0H1YOEPHRY1R2SN5B5RL@david.davidtw.co>

Update src/librustc_error_codes/error_codes/E0724.md
Co-authored-by: NDavid Wood <Q0KPU0H1YOEPHRY1R2SN5B5RL@david.davidtw.co>

Minor refactoring

Suggest including unused asm arguments in a comment to avoid error

We require all arguments to an `asm!` to be used in the template string, just like format strings. However in some cases (e.g. `black_box`) it may be desirable to have `asm!` arguments that are not used in the template string.

Currently this is a hard error rather than a lint since `#[allow]` does not work on macros (#63221), so this PR suggests using the unused arguments in an asm comment as a workaround.

r? @petrochenkov

Clean up E0648 explanation

r? @Dylan-DPC

Track span of function in method calls, and use this in #[track_caller]

Fixes #69977

When we parse a chain of method calls like `foo.a().b().c()`, each
`MethodCallExpr` gets assigned a span that starts at the beginning of
the call chain (`foo`). While this is useful for diagnostics, it means
that `Location::caller` will return the same location for every call
in a call chain.

This PR makes us separately record the span of the function name and
arguments for a method call (e.g. `b()` in `foo.a().b().c()`). This
`Span` is passed through HIR lowering and MIR building to
`TerminatorKind::Call`, where it is used in preference to
`Terminator.source_info.span` when determining `Location::caller`.

This new span is also useful for diagnostics where we want to emphasize
a particular method call - for an example, see
https://github.com/rust-lang/rust/pull/72389#discussion_r436035990

Handle assembler warnings properly

Previously all inline asm diagnostics were treated as errors, but LLVM sometimes emits warnings and notes as well.

Fixes #73160

r? @petrochenkov

Try_run must only be used if toolstate is populated

Clippy's tests were failing the build, but that failure was ignored in favor of checking toolstate. This is the correct behavior for toolstate-checked tools, but Clippy no longer updates its toolstate status as it should always build.

The previous PR of this kind didn't catch this as I expected x.py failures to always lead to a non-successful build in CI, but that's not the case specifically for tool testing.

Show `SyntaxContext` in formatted `Span` debug output

This is only really useful in debug messages, so I've switched to
calling `span_to_string` in any place that causes a `Span` to end up in
user-visible output.

remove extra space from crate-level doctest names

Before:

```
running 2 tests
test src/test/rustdoc-ui/doctest-output.rs - foo::bar (line 11) ... ok
test src/test/rustdoc-ui/doctest-output.rs -  (line 5) ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
```

After:

```
running 2 tests
test src/test/rustdoc-ui/doctest-output.rs - foo::bar (line 11) ... ok
test src/test/rustdoc-ui/doctest-output.rs - (line 5) ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
```

Given a code

```rust
fn foo(x: u8, y: u32) -> bool {
    x > y
}
fn main() {}
```

it could be more helpful to provide a suggestion to do "u32::from(x)"
rather than "y.try_into().unwrap()", since the latter may panic.

We do this by passing the LHS of a binary expression up the stack into
the coercion checker.

Closes #73145

Rollup of 11 pull requests

Successful merges:

 - #72380 (Fix `is_const_context`, update `check_for_cast`)
 - #72941 (Ensure stack when building MIR for matches)
 - #72976 (Clean up E0642 explanation)
 - #73080 (doc/rustdoc: Fix incorrect external_doc feature flag)
 - #73155 (save_analysis: better handle paths and functions signature)
 - #73164 (Add new E0762 error code)
 - #73172 (Fix more clippy warnings)
 - #73181 (Automatically prioritize unsoundness issues)
 - #73183 (Support proc macros in intra doc link resolution)
 - #73208 (Fix doctest template)
 - #73219 (x.py: with --json-output, forward cargo's JSON)

Failed merges:

r? @ghost

x.py: with --json-output, forward cargo's JSON

Fixes https://github.com/rust-lang/rust/issues/73209

r? @Mark-Simulacrum

Fix doctest template

`saturating_add` example was not parameterized, but passed because the `u8` would saturate successfully

Support proc macros in intra doc link resolution

The feature was written pre-proc macro resolution, so it only supported the wacky MBE resolution rules. This adds support for proc macros as well.

cc @GuillaumeGomez

Fixes #73173

Automatically prioritize unsoundness issues

r? @spastorino cc @Mark-Simulacrum @rust-lang/wg-prioritization

Fix more clippy warnings

Fixes more of:

clippy::unused_unit
clippy::op_ref
clippy::useless_format
clippy::needless_return
clippy::useless_conversion
clippy::bind_instead_of_map
clippy::into_iter_on_ref
clippy::redundant_clone
clippy::nonminimal_bool
clippy::redundant_closure
clippy::option_as_ref_deref
clippy::len_zero
clippy::iter_cloned_collect
clippy::filter_next

r? @Dylan-DPC

Add new E0762 error code

save_analysis: better handle paths and functions signature

This should improve slightly some possible regressions due to hir rework.

r? @Xanewok

doc/rustdoc: Fix incorrect external_doc feature flag

Clean up E0642 explanation

r? @Dylan-DPC

Ensure stack when building MIR for matches

In particular matching on complex types such as strings will cause
deep recursion to happen.

Fixes #72933

r? @matthewjasper @oli-obk

Fix `is_const_context`, update `check_for_cast`

A better version of #71477

Adds `fn enclosing_body_owner` and uses it in `is_const_context`.
`is_const_context` now uses the same mechanism as `mir_const_qualif` as it was previously incorrect.
Renames `is_const_context` to `is_inside_const_context`.

I also updated `check_for_cast` in the second commit, so r? @estebank

(I removed one lvl of indentation, so it might be easier to review by hiding whitespace changes)

Relate existential associated types with variance Invariant

Fixes #71550 #72315

r? @nikomatsakis

The test case reported in that issue now errors with the following message ...

```
error[E0495]: cannot infer an appropriate lifetime for lifetime parameter 'a in function call due to conflicting requirements
  --> /tmp/test.rs:25:5
   |
25 |     bad(&Bar(PhantomData), x)
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: first, the lifetime cannot outlive the lifetime `'a` as defined on the function body at 24:11...
  --> /tmp/test.rs:24:11
   |
24 | fn extend<'a, T>(x: &'a T) -> &'static T {
   |           ^^
note: ...so that reference does not outlive borrowed content
  --> /tmp/test.rs:25:28
   |
25 |     bad(&Bar(PhantomData), x)
   |                            ^
   = note: but, the lifetime must be valid for the static lifetime...
note: ...so that the types are compatible
  --> /tmp/test.rs:25:9
   |
25 |     bad(&Bar(PhantomData), x)
   |         ^^^^^^^^^^^^^^^^^
   = note: expected  `&'static T`
              found  `&T`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0495`.
```

I could also add that test case if we want to have a weaponized one too.