Proposed resolution:

Replace

-15- Effects: If InputIterator is an integral type, equivalent to

basic_string(static_cast<size_type>(begin), static_cast<value_type>(end))

with

-15- Effects: If InputIterator is an integral type, equivalent to

basic_string(static_cast<size_type>(begin), static_cast<value_type>(end), a)

The effects clause for the basic_string template ctor in 21.3.1, p15 leaves out the third argument of type Allocator. I believe this to be a mistake.