Re: New pattern matching doc

[Brian Goetz]

It is possible, but I think it's too subtle.  Everything else about 
pattern matching and assignment goes out of its way to not throw on 
failure, and this would undermine both of those.  I think your earlier 
comment about "specifically ask for it" is right.  The exact syntax of 
"specifically asking" surely admits many possibilities, but I think this 
particular mode of asking seems a little too much (actually, too little.)

There's no need to introduce new `try-match` syntax to opt into 
assignment to partial patterns, you can just lean on rules that users 
already understand. You ask for it simply by catching or throwing the 
potential exception.

    try {
PartialPattern(var a) = blah;
    } catch (MatchFailException e) {
    }

Is that not sufficient?