Polymorphic Data.Dynamic

At some point in the compilation process an expression acquires a fully-specified, possibly polymorphic, type. If we add an operation that join that type and that expresssion, say TypedAny, then we can implement the part of #4316 requested by mitar.

In GHCi we can evaluate HValues and also string them together with bind statements.

The function

applyDynamic :: TypedAny -> TypedAny -> Maybe TypedAny

includes in its implementation a dictionary lookup and possible dynamic object linking for class methods.

the function

fromDynamic :: TypedAny -> Maybe a

like applyDynamic, runs the typechecker at runtime to unify (and possibly link) the dynamic type (!TypedAny) and the static type (a).

*Conjecture * Since we already have typecase (classes), with type families, this feature provides/simulates dependent types.