[Grace-core] Gradual Typing for Generics

[Andrew P. Black]

On 15 Sep 2011, at 18:04, Kim Bruce wrote:

> On Sep 15, 2011, at 4:59 PM, Andrew P. Black wrote:
> 
>> 
>> If the type-checker can guarantee that a run-time type check will always fail, it's good to allow the programmer to be warned of this problem.  It's also good to allow the programmer to run the program anyway, and examine the dynamic error that is produced.  This error will provide a counterexample, and may make it a lot clearer why the program is wrong than any statically-produced textual error message
> 
> I think this is an implementation issue, but certainly sounds reasonable.  I believe Eclipse often asks if you want to try to run a program even if it has static errors (though most of the time that seems to fail when it actually attempts it).
> 
> Kim

I agree that It's an implementation issue _second_, but before that it's a semantic issue.  Is a program with a type error a program, or a non-program?  If we agree it's a program, and give it a semantics (like "Message-not-understood"), then it's possible for the implementation to run it (and, hopefully, produce  "MNU" as the answer!)  However, if we say that it's a non-program, then the implementation can't run it.

	Andrew