[GNATS 24964] Missing diagnostic for a private constructor

[jhsedg]

Customer bug ID

contract/test/specify-auto_error.test/specify-auto_error.cpp (and others), 24964.C, _24964.C

Description

​This is only in C++14 mode.
​
​class specify_precondition_old_postcondition_except {
​ specify_precondition_old_postcondition_except(
​ specify_precondition_old_postcondition_except const &);
​};
​specify_precondition_old_postcondition_except function();
​auto c = function();
​
​We do not generate the expected diagnostic.
​https://godbolt.org/z/z6YbcbxeT