A template is implicitly instantiated because of a "pointer conversion" on an argument. This was intended to include related-class conversions, but it also inadvertently includes conversions to void*, null pointer conversions, cv-qualification conversions and the identity conversion.

It is not clear whether a reinterpret_cast of a pointer should cause implicit instantiation.

Proposed resolution (10/01): Replace 13.9.2 [temp.inst] paragraph 4, up to the example, with the following:

A class template specialization is implicitly instantiated if the class type is used in a context that requires a completely-defined object type or if the completeness of the class type might affect the semantics of the program. [Note: in particular, if the semantics of an expression depend on the member or base class lists of a class template specialization, the class template specialization is implicitly generated. For instance, deleting a pointer to class type depends on whether or not the class declares a destructor, and conversion between pointer to class types depends on the inheritance relationship between the two classes involved. ]

This version differs from the previous version is its use of the word "might" in the first sentence.

(See also issue 212.)