[m-dev.] RTTI & breaching the abstraction barrier

[Ralph Becket]

This has been bugging me for a while, so I thought I'd mention it.

The type reflection stuff in std_util allows a programmer to pick
apart an object whose composition would normally be hidden because
the object's type is abstract.

What's worse, it seems that a sneaky programmer can also construct
objects of the abstract type and place them in circulation.  This
can cause problems.  For instance, set/1 is an abstract type
implemented as an ordered list; using construct/3 I can create an
instance of set/1 that does not satisfy this property.

Admittedly this would be an odd thing to do, but it is a hole.

Is this a hole to be plugged (I'd be interested in the mechanism)
or a necessary evil?  [Disclaimer: I think RTTI is a Good Thing!]

--
Ralph Becket      |      MSR Cambridge      |      rbeck at microsoft.com 
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