[llvm] r264135 - [Docs] Clarify boolean conversion for Error and Expected<T> in the Programmer's

[Rafael Espíndola via llvm-commits]

Should we use 'auto' in code that that?

Cheers,
Rafael


On 22 March 2016 at 23:18, Lang Hames via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: lhames
> Date: Tue Mar 22 22:18:16 2016
> New Revision: 264135
>
> URL: http://llvm.org/viewvc/llvm-project?rev=264135&view=rev
> Log:
> [Docs] Clarify boolean conversion for Error and Expected<T> in the Programmer's
> Manual.
>
>
> Modified:
>     llvm/trunk/docs/ProgrammersManual.rst
>
> Modified: llvm/trunk/docs/ProgrammersManual.rst
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ProgrammersManual.rst?rev=264135&r1=264134&r2=264135&view=diff
> ==============================================================================
> --- llvm/trunk/docs/ProgrammersManual.rst (original)
> +++ llvm/trunk/docs/ProgrammersManual.rst Tue Mar 22 22:18:16 2016
> @@ -356,12 +356,24 @@ that inherits from the ErrorInfo utility
>      return Error::success();
>    }
>
> +Error values can be implicitly converted to bool: true for error, false for
> +success, enabling the following idiom:
> +
> +.. code-block::
> +
> +  if (auto Err = mayFail())
> +    return Err;
> +
> +  // Success! We can proceed.
> +
> +
>  For functions that can fail but need to return a value the ``Expected<T>``
>  utility can be used. Values of this type can be constructed with either a
> -``T``, or a ``Error``. Values are implicitly convertible to boolean: true
> -for success, false for error. If success, the ``T`` value can be accessed via
> -the dereference operator. If failure, the ``Error`` value can be extracted
> -using the ``takeError()`` method:
> +``T``, or a ``Error``. Expected<T> values are also implicitly convertible to
> +boolean, but with the opposite convention to Error: true for success, false for
> +error. If success, the ``T`` value can be accessed via the dereference operator.
> +If failure, the ``Error`` value can be extracted using the ``takeError()``
> +method. Idiomatic usage looks like:
>
>  .. code-block:: c++
>
>
>
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