False non-virtual dtor warning when passing structs or using nested classes

[warmsocks]

The following four test cases all cause Flint++ to generate the warning "Classes with virtual functions should not have a public non-virtual destructor" erroneously, I believe. In three of the cases a struct is being returned from or passed to a method. In the last one there is a class inside another class. Strangely the warnings go away if the line following the one causing the warning is deleted or commented out.

To reproduce, run flint++ in the same directory as the following four header files

$ ~/cpp/flint++_false_vdtors$ flint++ -l3
[Warning] cev.h:12: Classes with virtual functions should not have a public non-virtual destructor.
[Warning] no_ctor.h:12: Classes with virtual functions should not have a public non-virtual destructor.
[Warning] no_ctor.h:15: Classes with virtual functions should not have a public non-virtual destructor.
[Warning] pd.h:9: Classes with virtual functions should not have a public non-virtual destructor.
[Warning] struct_return.h:12: Classes with virtual functions should not have a public non-virtual destructor.

Lint Summary: 4 files
Errors: 0 Warnings: 5 Advice: 0

Estimated Lines of Code: 72

Instead, I would expect no warnings.

CentOS Linux release 7.6.1810 (Core)
g++ (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36)

#ifndef CEV_H
#define CEV_H

#include <time.h>

class A
{
public:
    A() {}
    virtual ~A() {}

    virtual struct timeval getLastUpdate() { timeval t; return t; } // [Warning] cev.h:12: Classes with virtual functions should not have a public non-virtual destructor.
    virtual void m() {} // Deleting or commenting out this line gets rid of the warning in the line above
};

#endif /* CEV_H */

#ifndef FOO_H
#define FOO_H

#include <sys/time.h>

struct Z { int i, j; };

class Foo 
{
public:
    virtual ~Foo() {}
    virtual void bar(struct timeval timestamp) {} // [Warning] no_ctor.h:12: Classes with virtual functions should not have a public non-virtual destructor.

    virtual void bar(Z z) {}         // No warning
    virtual void bar(struct Z& z) {} // [Warning] no_ctor.h:15: Classes with virtual functions should not have a public non-virtual destructor.
    virtual void baz() {}            // Removing this line gets rid of the warning for the line above
};

#endif /* FOO_H */

#ifndef STRUCT_RETURN_H
#define STRUCT_RETURN_H

#include <time.h>

class C
{
public:
    C() {}
    virtual ~C() {}

    virtual struct timeval getLastUpdate() { return {0,0}; } // [Warning] struct_return.h:12: Classes with virtual functions should not have a public non-virtual destructor.

    virtual bool foo(); // Deleting or commenting this line gets rid of the warning in the line above
};
#endif /* STRUCT_RETURN_H */

#ifndef PD_H
#define PD_H

class B
{
public:
    virtual ~B();

    class C // [Warning] pd.h:9: Classes with virtual functions should not have a public non-virtual destructor.
    {   
    public:
        C() {}
    };  

    virtual bool foo(); // Deleting or commenting this line gets rid of the warning in the line above
};
#endif /* PD_H */