Cannot generate `typeinfo` for `HardwareSerial` without at least one method default defined

[mathemaphysics]

Is your feature request related to a problem? Please describe.
Yes. In order to generate typeinfo for the HardwareSerial class (even with -frtti enabled), there must be a default empty definition somewhere of the HardwareSerial::begin(unsigned int) method (at least). I chose this one arbitrarily. Without these typeinfo symbols I can't dynamic_cast anything involving HardwareSerial.

Describe the solution you'd like
Add a HardwareSerial.cpp file with an empty definition of the previously mentioned begin method. Unfortunately the compiler won't take the hint from HardwareSerial.h in which

class HardwareSerial : public Stream
{
  public:
    virtual void begin(unsigned long);

};

becomes

class HardwareSerial : public Stream
{
  public:
    virtual void begin(unsigned long baudrate) {} // Now it's defined
};

because this is "inline" and apparently doesn't qualify as a sufficient indicator to allow RTTI to generate the typeinfo.

Describe alternatives you've considered
I've simply added my explicit default definition of HardwareSerial::begin(unsigned int) in another source file. This works, but it feels like this should be a part of the library because it serves as an abstract class.

Additional context
This issue isn't terribly important, but I will say that the ESP32 and ItsyBitsyM4 frameworks don't run into this problem at all. And it's an easy fix.

I can also submit the fix myself.