In C++17, when class C has large alignment value, a special case of overload resolution rule kicks in for expression new C that causes the aligned version of operator new() to be called. The aligned new has two arguments: size and alignment. However, the new-expression has only one argument: the construct-expression for C(). This causes a false positive in core.CallAndMessage's check for matching number of arguments and number of parameters.
Update CXXAllocatorCall, which is a CallEvent sub-class for operator new calls within new-expressions, so that the number of arguments always matched the number of parameters.
Dunno, maybe we should instead abandon the idea of reserving a whole argument/parameter index for each of those implicit arguments that aren't even represented by an expression in the AST.
Side note: Ugh, we never supported passing size into operator new() calls, even though it's known in compile time. And now also alignment. They are currently symbolic (unconstrained) within allocator calls.