Shorten even more panic temporary lifetimes

[dtolnay]

Followup to #104134. As pointed out by @bjorn3 in #104134 (review), 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:

tests/ui/macros/panic-temporaries-2018.rs

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

tests/ui/macros/panic-temporaries.rs

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

r? bjorn3

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[bjorn3]

@bors r+

[bors]

📌 Commit 2f5d993 has been approved by bjorn3

It is now in the queue for this repository.

[bors]

⌛ Testing commit 2f5d993 with merge 2d17294...

[bors]

☀️ Test successful - checks-actions
Approved by: bjorn3
Pushing 2d17294 to master...

[rust-timer]

Finished benchmarking commit (2d17294): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.6%	[-5.6%, -5.6%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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Bootstrap: 641.09s -> 640.861s (-0.04%)