Clean build test failures?

Hello,

I’m seeing three recent test failures that don’t go away after a clean build, including deleting the module cache beforehand:

Failing Tests (3):
    Swift(macosx-x86_64) :: Serialization/Recovery/typedefs.swift
    Swift(macosx-x86_64) :: Serialization/extension-of-typealias.swift
    Swift(macosx-x86_64) :: IDE/print_module_comments.swift

Any idea what might be going on? This is Xcode 9C40b if it matters.

Thanks,
Dave