Yes- but not only are C# and Java faster to compile in general, they're easier to process small pieces of in isolation. C++ requires everything referenced to be

Yes- but not only are C# and Java faster to compile in general, they're easier to process small pieces of in isolation. C++ requires everything referenced to be declared previously even just to parse. (Modules should help here, at least, eventually.) But even then, parsing is often required to do complex Turing-complete processing of templates and constexpr, since that determines something's role in the grammar. This forces an accuracy vs performance tradeoff that modules don't help with at all. So it's not just a compile time problem that happens to affect IDEs, but also an IDE problem, because they can't take nearly as much advantage of the fact that they're only trying to analyze the code, not build it. And language extensions are hardly unfair. In practice they're used all over the place, and people expect them to work in their IDEs, especially when they're off in some header they didn't write. (Attributes help here, somewhat, when compiler vendors can move extensions into them.)