If a compilation unit has a class A:

MODULES_EXPORT class A : public Base<int> {};

and a class B through a header:

CORE_EXPORT class B : public Base<int> {};

there will be link errors in Windows because there will be strongly defined symbols for Base<int> that will collide with the exported symbols in blinkcore.dll.

I don't know if this is a compiler bug in Visual Studio or something else, but it triggers if jumbo compiling modules/webaudio because the class WindowAudioWorklet inherits from Supplement<LocalDOMWindow> in the way described above.