Rationale (November, 2016):

The adoption of paper P0035R4 has rendered this issue moot.

According to 7.6.2.9 [expr.delete] paragraph 10, deletion of an array of a class with both sized and non-sized deallocation functions is not required to call the sized version if the destructor is trivial:

If deallocation function lookup finds both a usual deallocation function with only a pointer parameter and a usual deallocation function with both a pointer parameter and a size parameter, the function to be called is selected as follows:

• If the type is complete and if, for the second alternative (delete array) only, the operand is a pointer to a class type with a non-trivial destructor or a (possibly multi-dimensional) array thereof, the function with two parameters is selected.

• Otherwise, it is unspecified which of the two deallocation functions is selected.

However, if only a sized deallocation function is specified as a class-specific deallocation function, it is not clear how the size argument is to be determined if the class has a trivial destructor.