[swift-evolution] Proposal: Initialization should not be required in precondition(false) case.

[Chris Lattner]

On Feb 12, 2016, at 9:27 AM, Amir Michail <a.michail at me.com> wrote:
>>> 
>>> What’s wrong with having the compiler explicitly check for “false”?
>> 
>> Weird special cases make the compiler less predictable.
> 
> True, but not having them requires deeper knowledge of the standard libraries.
> 
> In practice, just checking for “false” would solve this problem.

That is not what you’re actually proposing.  You are proposing that the compiler encode special knowledge of the precondition *library function* into the compiler, and teach it about a single special case.  We don’t like the compiler to have special cases like this for a large number of reasons, in particular, if we did this, someone would file a bug asking for *their* equivalent reimplementation of precondition to have the same magic blessed behavior. 

This is a slippery slope that leads to a lot of complexity downstream, it is better to keep the compiler simple and predictable.  Also, as other people have pointed out, this has already been solved for you: just use preconditionFailure.

-Chris