C++ has header file, which is extremely bad for compile time. You can engineer around it (for example, see Zapcc, which is 4x faster than clang) but it's so difficult most don't. Since Swift does not have header file, even if Swift is higher level Swift should be faster to compile. The fact that it isn't, IMO, indicates problems in Swift frontend (which is, NOT shared with clang, hence NOT the same compiler infrastructure).
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C++ has header file, which is extremely bad for compile time. You can engineer around it (for example, see Zapcc, which is 4x faster than clang) but it's so difficult most don't. Since Swift does not have header file, even if Swift is higher level Swift should be faster to compile. The fact that it isn't, IMO, indicates problems in Swift frontend (which is, NOT shared with clang, hence NOT the same compiler infrastructure).
Unfortunately the problem here happens to be of a theoretical nature and not something a few years of engineering can reasonably fix.