[racket] Unsafe version of require/typed?

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Fri Mar 20 16:45:10 EDT 2015

I think we should think the best of our users and not assume that we
know better than they do about what they need to do their work.

In this particular case, they can always opt out of tr entirely, lets
not forget.


On Fri, Mar 20, 2015 at 3:41 PM, Alexis King <lexi.lambda at gmail.com> wrote:
> This has been discussed before, and I think it’s a good idea, but I also think any such feature should be well-hidden. I’m sure that new users would use it frequently just to make the typechecker “shut up” when really their programs are unsound.
>> On Mar 20, 2015, at 12:30, Hendrik Boom <hendrik at topoi.pooq.com> wrote:
>> On Fri, Mar 20, 2015 at 03:20:38PM -0400, Eric Dong wrote:
>>> It would be nice if we could have an unsafe version of require/typed, which
>>> doesn't generate a contract, but simply "lies" to the type system about the
>>> type. This, of course, breaks the type system's guarantees, and causes UB
>>> if optimizations are one, but in some cases contracts cannot be generated
>>> (for example, for the "object-name" function), but one can create a safe
>>> type for it.
>>> Why can't there be a "require/typed/unsafe" form? It could save a lot of
>>> unnecessary asserts and casts, and unnecessary contract overhead.
>> Perhaps this model can provide guidance:
>> If I recall correctly, Modula 3, another garbage-collected, strongly
>> typed language, has unsafe interfaces and, separately, unsafe
>> implementations.
>> You can implement a safe (i.e., ordinary) interface with an unsafe
>> implementation.  This means that it is the implementer's
>> (not  the compiler's) responsibility to make sure that the the module
>> will perform all necessary run-time checks to make sure that it can
>> only be used safely, but the implementation can use unsafe language
>> features.
>> An unsafe interface, on the other hand, can only be used in an unsafe
>> implementation.
>> -- hendrik
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