Performance of pattern checker on OptCoercions

Richard Eisenberg eir at
Mon Dec 14 14:03:23 UTC 2015

On Dec 13, 2015, at 1:07 PM, George Karachalias <george.karachalias at> wrote:

> Sounds nice and I think it is much better than giving up guards completely. The only thing I
> don't like much is having so many different flags concerning the check because I don't want
> it to become "too complex" for users. I guess we have to live with it though :)

Yes. I'd like this to be simpler. Perhaps there is a way to combine all of this into one flag. I see 4 settings:

1. No guard match checking.
2. Check guards; bail and issue warning on tough cases.
3. Check guards; bail with no warning on tough cases.
4. Check guards at any cost.

We could have these be

1. -fwarn-pattern-guards=none
2. -fwarn-pattern-guards=try
3. -fwarn-pattern-guards=try-quiet
4. -fwarn-pattern-guards=do   -- there is no "try"

Is that simpler? Maybe.


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