PODs, non-PODs, rvalue and lvalues

Question

Could anyone explain the details in terms of rvalues, lvalues, PODs, and non-PODs the reason why the first expression marked below is not ok while the secon

Answer 1

From Does C++ do value initialization of a POD typedef?, which quotes the Standard:

The expression T(), where T is a simple-type-specifier (7.1.5.2) for a non-array complete object type or the (possibly cv-qualified) void type, creates an rvalue of the specified type, which is value-initialized

Therefore int() is an rvalue and can't be assigned to, as you saw in your first case.

A() would not be a simlle-type-specifyer and thus A() yields an lvalue