There are times where computing a value may be cheap, or where
computing a reference may be expensive, so this fills out the
possibilities.

…ref_of}`

While the `provide_*` methods already short-circuit when a value has
been provided, there are times where an expensive computation is
needed to determine if the `provide_*` method can even be called.

Before, the MIR validator used RevealAll in its ParamEnv for type
checking. This could cause false negatives in some cases due to
RevealAll ParamEnvs not always use all predicates as expected here.

Since some MIR passes like inlining use RevealAll as well, keep using
it in the MIR validator too, but when it fails usign RevealAll, also
try the check without it, to stop false negatives.

Before, it called `normalize_erasing_regions` twice since
`equal_up_to_regions` called it as well for both types.

`std::os::fd` defines types like `OwnedFd` and `RawFd` and is common
between Unix and non-Unix platforms that share a basic file-descriptor
concept. Rust currently uses this internally to simplify its own code,
but it would be useful for external users in the same way, so make it
public.

This means that `OwnedFd` etc. will all appear in three places, for
example on unix platforms:
 - `std::os::fd::OwnedFd`
 - `std::os::unix::io::OwnedFd`
 - `std::os::unix::prelude::OwnedFd`

Add `#[unstable(feature = "os_fd", issue = "98699")]` to the new
`pub use` declarations.

Previously we were just using the parent node as the scope for a
temporary value, but it turns out this is too narrow. For example, in
an expression like

    Foo {
        b: &42,
        a: async { 0 }.await,
    }

the scope for the &42 was set to the ExprField node for `b: &42`, when
we actually want to use the Foo struct expression.

We fix this by recursively searching through parent nodes until we find
a Node::Expr. It may be that we don't find one, and if so that's okay,
we will just fall back on the enclosing temporary scope which is always
sufficient.

revealed by tests, manually add a panic to test for dead code

…ossible...

- ... when creating diagnostics in rustc_metadata
-  use the error_code! macro
- pass macro output to diag.code()
- use fluent from within manual implementation of SessionDiagnostic
- emit the untested errors in case they occur in the wild
- stop panicking in the probably-not-dead code, add fixme to write test

Walkthrough currently say:

```
rustup target add aarch_64-fuchsia
```
but should say

```
rustup target add aarch64-fuchsia
```

…r=joshtriplett

Make `std::os::fd` public.

`std::os::fd` defines types like `OwnedFd` and `RawFd` and is common
between Unix and non-Unix platforms that share a basic file-descriptor
concept. Rust currently uses this internally to simplify its own code,
but it would be useful for external users in the same way, so make it
public.

This means that `OwnedFd` etc. will all appear in three places, for
example on unix platforms:
 - `std::os::fd::OwnedFd`
 - `std::os::unix::io::OwnedFd`
 - `std::os::unix::prelude::OwnedFd`

r? ``````@joshtriplett``````

Add additional methods to the Demand type

This adds on to the original tracking issue rust-lang#96024

r? ``````@yaahc``````

… r=oli-obk

Try normalizing types without RevealAll in ParamEnv in MIR validation

Before, the MIR validator used RevealAll in its ParamEnv for type
checking. This could cause false negatives in some cases due to
RevealAll ParamEnvs not always use all predicates as expected here.

Since some MIR passes like inlining use RevealAll as well, keep using
it in the MIR validator too, but when it fails usign RevealAll, also
try the check without it, to stop false negatives.

Fixes rust-lang#99866

cc `````@compiler-errors````` who nicely helped me on zulip

…s, r=davidtwco

Migrate rustc_metadata to SessionDiagnostics

Migrate rustc_metadata to SessionDiagnostics.

Part of rust-lang#100717

[drop tracking] Use parent expression for scope, not parent node

Previously we were just using the parent node as the scope for a temporary value, but it turns out this is too narrow. For example, in an expression like

    Foo {
        b: &42,
        a: async { 0 }.await,
    }

the scope for the &42 was set to the ExprField node for `b: &42`, when we actually want to use the Foo struct expression.

We fix this by recursively searching through parent nodes until we find a Node::Expr. It may be that we don't find one, and if so that's okay, we will just fall back on the enclosing temporary scope which is always sufficient.

Helps with rust-lang#97331

r? `@jyn514`

…re-whitespace, r=notriddle

Remove unneeded where whitespace

It fixes these two bugs:

![Screenshot from 2022-08-31 18-14-40](https://user-images.githubusercontent.com/3050060/187727950-94657419-abfa-454c-9d27-004280fbcb45.png)
![Screenshot from 2022-08-31 18-14-49](https://user-images.githubusercontent.com/3050060/187727956-21d1b39d-62d7-4e7b-8f6f-631ceda67a19.png)

It's a relic from a very old time (this commit: rust-lang@bfd01b7).

You can test the result [here](https://rustdoc.crud.net/imperio/remove-unneeded-where-whitespace/lib2/struct.WhereWhitespace.html).

cc ``````@jsha``````
r? ``````@notriddle``````

Fix  bad target name in Walkthrough

Walkthrough currently say:

```
rustup target add aarch_64-fuchsia
```
but should say

```
rustup target add aarch64-fuchsia
```

… r=tmandry

Fixes/adjustments to Fuchsia doc walkthrough

Small fixes/adjustments missed during rust-lang#100927