[racket] Unsafe version of require/typed?

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