Allow ambiguous types (with warning) by default

Edward Kmett ekmett at
Sun Dec 6 04:51:43 UTC 2015

So you are saying you want users to write a ton of code that happens to
have signatures that can never be called and only catch it when they go to
try to actually use it in a concrete situation much later?

I don't really show how this would be a better default.

When and if users see the problem later they have to worry about if they
are doing something wrong at the definition site or the call site. With the
status quo it complains at the right time that you aren't going to sit
there flailing around trying to fix a call site that can never be fixed.


On Sat, Dec 5, 2015 at 5:38 PM, David Feuer <david.feuer at> wrote:

> The ambiguity check produces errors that are quite surprising to the
> uninitiated. When the check is suppressed, the errors at use sites are
> typically much easier to grasp. On the other hand, there's obviously a lot
> of value to catching mistakes as soon as possible. Would it be possible to
> turn that into a warning by default?
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