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Include output stream in panic!() documentation #83254

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Mar 20, 2021
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Include output stream in panic!() documentation #83254

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55d9e0f
Include output stream in `panic!()` documentation
jfrimmel Mar 18, 2021
61e5d54
Add more information about panicking
jfrimmel Mar 18, 2021
d5e45b5
Incorporate review feedback #2
jfrimmel Mar 18, 2021
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Apply suggestions from code review
jfrimmel Mar 18, 2021
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15 changes: 10 additions & 5 deletions library/core/src/macros/panic.md
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Expand Up @@ -9,11 +9,15 @@ tests. `panic!` is closely tied with the `unwrap` method of both
[`Option`][ounwrap] and [`Result`][runwrap] enums. Both implementations call
`panic!` when they are set to [`None`] or [`Err`] variants.

This macro is used to inject panic into a Rust thread, causing the thread to
panic entirely. This macro panics with a string and uses the [`format!`] syntax
for building the message.

Each thread's panic can be reaped as the [`Box`]`<`[`Any`]`>` type,
When using `panic!()` you can specify a string payload, that is built using
the [`format!`] syntax. That payload is used when injecting the panic into
the calling Rust thread, causing the thread to panic entirely.

The behavior of the default `std` hook, i.e. the code that runs directly
after the panic is invoked, is to print the message payload to
`stderr` along with the file/line/column information of the `panic!()`
call. You can override the panic hook using [`std::panic::set_hook()`].
Inside the hook a panic can be accessed as a `&dyn Any + Send`,
which contains either a `&str` or `String` for regular `panic!()` invocations.
To panic with a value of another other type, [`panic_any`] can be used.

Expand All @@ -26,6 +30,7 @@ See also the macro [`compile_error!`], for raising errors during compilation.

[ounwrap]: Option::unwrap
[runwrap]: Result::unwrap
[`std::panic::set_hook()`]: ../std/panic/fn.set_hook.html
[`panic_any`]: ../std/panic/fn.panic_any.html
[`Box`]: ../std/boxed/struct.Box.html
[`Any`]: crate::any::Any
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