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Write documentation for the Termination trait #740

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Write documentation for the Termination trait #740

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Write documentation for the Termination trait
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@LeSeulArtichaut
LeSeulArtichaut committed Jan 25, 2020
commit a8c2109690cc59f2f2c98a2bd0970478538e2401
25 changes: 25 additions & 0 deletions src/special-types-and-traits.md
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Expand Up @@ -139,13 +139,37 @@ compile-time; that is, it's not a [dynamically sized type]. [Type parameters]
are `Sized` by default. `Sized` is always implemented automatically by the
compiler, not by [implementation items].

## `Termination`

Types implementing the [`Termination`] trait can be returned from `main()`.
Those types implement logic to be converted to an integer value returned
to the operating system when the program ends.

The standard library has implementations for the following types:

* [`ExitCode`] represents conventional return values, depending on the
operating system. This includes `SUCCESS` and `FAILURE` variants, but
could be extanded in the future.
* `()` returns `ExitCode::SUCCESS`
* `Result<(), E>` returns `ExitCode::SUCCESS` for an `Ok` variant,
and prints an error before exiting with `ExitCode::FAILURE` for an
`Err` variant.
* [`!`] cannot be constructed, thus can never be returned. Using this as a
return type for `main()` denotes that the program will run forever, unless
it is interrupted by the operating system.
* `Result<!, E>` prints the `Err` and exits with `ExitCode::FAILURE` when
returned, since the `Ok` variant containts [`!`] cannot be constructed.
Using this as return type for `main()` denotes that the program will run forever,
unless it is interrupted or it encounters an error

[`Arc<Self>`]: ../std/sync/struct.Arc.html
[`Box<T>`]: ../std/boxed/struct.Box.html
[`Clone`]: ../std/clone/trait.Clone.html
[`Copy`]: ../std/marker/trait.Copy.html
[`Deref`]: ../std/ops/trait.Deref.html
[`DerefMut`]: ../std/ops/trait.DerefMut.html
[`Drop`]: ../std/ops/trait.Drop.html
[`ExitCode`]: ../std/process/struct.ExitCode.html
[`Pin<P>`]: ../std/pin/struct.Pin.html
[`Rc<Self>`]: ../std/rc/struct.Rc.html
[`RefUnwindSafe`]: ../std/panic/trait.RefUnwindSafe.html
Expand All @@ -157,6 +181,7 @@ compiler, not by [implementation items].
[`std::ops`]: ../std/ops/index.html
[`UnwindSafe`]: ../std/panic/trait.UnwindSafe.html
[`Sync`]: ../std/marker/trait.Sync.html
[`Termination`]: ../std/process/trait.Termination.html

[Arrays]: types/array.md
[call expressions]: expressions/call-expr.md
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