How do you force constructor signatures and static methods?

Question

Is there a way of forcing a (child) class to have constructors with particular signatures or particular static methods in C# or Java?

You can't obviously use interfaces for this, and I know that it will have a limited usage. One instance in which I do find it useful is when you want to enforce some design guideline, for example:

Exceptions
They should all have the four canonical constructors, but there is no way to enforce it. You have to rely on a tool like FxCop (C# case) to catch these.

Operators
There is no contract that specifies that two classes can be summed (with operator+ in C#)

Is there any design pattern to work around this limitation? What construct could be added to the language to overcome this limitation in future versions of C# or Java?

Answer 1

Not enforced at compile-time, but I have spent a lot of time looking at similar issues; a generic-enabled maths library, and an efficient (non-default) ctor API are both avaiable in MiscUtil. However, these are only checked at first-usage at runtime. In reality this isn't a big problem - your unit tests should find any missing operator / ctor very quickly. But it works, and very quickly...