Auto merge of #111590 - dtolnay:panictemporaries, r=bjorn3

Shorten even more panic temporary lifetimes

Followup to #104134. As pointed out by `@bjorn3` in https://github.com/rust-lang/rust/pull/104134#pullrequestreview-1425585948, there are other cases in the panic macros which would also benefit from dropping their non-Send temporaries as soon as possible, avoiding pointlessly holding them across an await point.

For the tests added in this PR, here are the failures you get today on master without the macro changes in this PR:

<details>
<summary>tests/ui/macros/panic-temporaries-2018.rs</summary>

```console
error: future cannot be sent between threads safely
  --> tests/ui/macros/panic-temporaries-2018.rs:52:18
   |
LL |     require_send(panic_display());
   |                  ^^^^^^^^^^^^^^^ future returned by `panic_display` is not `Send`
   |
   = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `*const u8`
note: future is not `Send` as this value is used across an await
  --> tests/ui/macros/panic-temporaries-2018.rs:35:31
   |
LL |     f(panic!("{}", NOT_SEND)).await;
   |                    --------   ^^^^^- `NOT_SEND` is later dropped here
   |                    |          |
   |                    |          await occurs here, with `NOT_SEND` maybe used later
   |                    has type `NotSend` which is not `Send`
note: required by a bound in `require_send`
  --> tests/ui/macros/panic-temporaries-2018.rs:48:25
   |
LL | fn require_send(_: impl Send) {}
   |                         ^^^^ required by this bound in `require_send`

error: future cannot be sent between threads safely
  --> tests/ui/macros/panic-temporaries-2018.rs:52:18
   |
LL |     require_send(panic_display());
   |                  ^^^^^^^^^^^^^^^ future returned by `panic_display` is not `Send`
   |
   = help: within `NotSend`, the trait `Sync` is not implemented for `*const u8`
note: future is not `Send` as this value is used across an await
  --> tests/ui/macros/panic-temporaries-2018.rs:35:31
   |
LL |     f(panic!("{}", NOT_SEND)).await;
   |       ----------------------  ^^^^^- the value is later dropped here
   |       |                       |
   |       |                       await occurs here, with the value maybe used later
   |       has type `&NotSend` which is not `Send`
note: required by a bound in `require_send`
  --> tests/ui/macros/panic-temporaries-2018.rs:48:25
   |
LL | fn require_send(_: impl Send) {}
   |                         ^^^^ required by this bound in `require_send`

error: future cannot be sent between threads safely
  --> tests/ui/macros/panic-temporaries-2018.rs:53:18
   |
LL |     require_send(panic_str());
   |                  ^^^^^^^^^^^ future returned by `panic_str` is not `Send`
   |
   = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `*const u8`
note: future is not `Send` as this value is used across an await
  --> tests/ui/macros/panic-temporaries-2018.rs:40:36
   |
LL |     f(panic!((NOT_SEND, "...").1)).await;
   |               --------             ^^^^^- `NOT_SEND` is later dropped here
   |               |                    |
   |               |                    await occurs here, with `NOT_SEND` maybe used later
   |               has type `NotSend` which is not `Send`
note: required by a bound in `require_send`
  --> tests/ui/macros/panic-temporaries-2018.rs:48:25
   |
LL | fn require_send(_: impl Send) {}
   |                         ^^^^ required by this bound in `require_send`

error: future cannot be sent between threads safely
  --> tests/ui/macros/panic-temporaries-2018.rs:54:18
   |
LL |     require_send(unreachable_display());
   |                  ^^^^^^^^^^^^^^^^^^^^^ future returned by `unreachable_display` is not `Send`
   |
   = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `*const u8`
note: future is not `Send` as this value is used across an await
  --> tests/ui/macros/panic-temporaries-2018.rs:45:31
   |
LL |     f(unreachable!(NOT_SEND)).await;
   |                    --------   ^^^^^- `NOT_SEND` is later dropped here
   |                    |          |
   |                    |          await occurs here, with `NOT_SEND` maybe used later
   |                    has type `NotSend` which is not `Send`
note: required by a bound in `require_send`
  --> tests/ui/macros/panic-temporaries-2018.rs:48:25
   |
LL | fn require_send(_: impl Send) {}
   |                         ^^^^ required by this bound in `require_send`

error: future cannot be sent between threads safely
  --> tests/ui/macros/panic-temporaries-2018.rs:54:18
   |
LL |     require_send(unreachable_display());
   |                  ^^^^^^^^^^^^^^^^^^^^^ future returned by `unreachable_display` is not `Send`
   |
   = help: within `NotSend`, the trait `Sync` is not implemented for `*const u8`
note: future is not `Send` as this value is used across an await
  --> tests/ui/macros/panic-temporaries-2018.rs:45:31
   |
LL |     f(unreachable!(NOT_SEND)).await;
   |       ----------------------  ^^^^^- the value is later dropped here
   |       |                       |
   |       |                       await occurs here, with the value maybe used later
   |       has type `&NotSend` which is not `Send`
note: required by a bound in `require_send`
  --> tests/ui/macros/panic-temporaries-2018.rs:48:25
   |
LL | fn require_send(_: impl Send) {}
   |                         ^^^^ required by this bound in `require_send`

error: aborting due to 5 previous errors
```
</details>

<details>
<summary>tests/ui/macros/panic-temporaries.rs</summary>

```console
error: future cannot be sent between threads safely
  --> tests/ui/macros/panic-temporaries.rs:42:18
   |
LL |     require_send(panic_display());
   |                  ^^^^^^^^^^^^^^^ future returned by `panic_display` is not `Send`
   |
   = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `*const u8`
note: future is not `Send` as this value is used across an await
  --> tests/ui/macros/panic-temporaries.rs:35:31
   |
LL |     f(panic!("{}", NOT_SEND)).await;
   |                    --------   ^^^^^- `NOT_SEND` is later dropped here
   |                    |          |
   |                    |          await occurs here, with `NOT_SEND` maybe used later
   |                    has type `NotSend` which is not `Send`
note: required by a bound in `require_send`
  --> tests/ui/macros/panic-temporaries.rs:38:25
   |
LL | fn require_send(_: impl Send) {}
   |                         ^^^^ required by this bound in `require_send`

error: future cannot be sent between threads safely
  --> tests/ui/macros/panic-temporaries.rs:42:18
   |
LL |     require_send(panic_display());
   |                  ^^^^^^^^^^^^^^^ future returned by `panic_display` is not `Send`
   |
   = help: within `NotSend`, the trait `Sync` is not implemented for `*const u8`
note: future is not `Send` as this value is used across an await
  --> tests/ui/macros/panic-temporaries.rs:35:31
   |
LL |     f(panic!("{}", NOT_SEND)).await;
   |       ----------------------  ^^^^^- the value is later dropped here
   |       |                       |
   |       |                       await occurs here, with the value maybe used later
   |       has type `&NotSend` which is not `Send`
note: required by a bound in `require_send`
  --> tests/ui/macros/panic-temporaries.rs:38:25
   |
LL | fn require_send(_: impl Send) {}
   |                         ^^^^ required by this bound in `require_send`

error: aborting due to 2 previous errors
```
</details>

r? bjorn3

0 files changed, 0 insertions, 0 deletions