[External] : Re: Remainder in pattern matching

[Brian Goetz]

Yes, and this is a special case of a more general thing -- that while 
pattern declarations may have a lot in common with methods, they are not 
"just methods with multiple return" (e.g., they have a different set of 
characteristics at the declaration, they are intrinsically conditional, 
they are "invoked" differently.)  While their bodies may look 
method-like, and ultimately they boil down to methods, thinking "they 
are just methods" is likely to drag you to the wrong place.  Of course, 
its a balance between how similar and HOW DIFFERENT they are, and that's 
what we're looking for.

>> Another thing it gains is that it discourages people
>> from thinking they can use exceptions in dtors; having these laundered
>> through MatchException discourages using this as a side channel, though
>> that's a more minor thing.
> This is a stronger argument than you give it credit for being.
> Wrapping the exception adds a bit of friction to doing the wrong thing
> which will pay off in helping guide users to the intended behaviour.