I agree, this and the long standing auto-balancing brackets bug takes away a lot of the joy from my work days ...
It would be great if someone could look into SR-10461, keeping in mind that it's not specific to the new SIMD types, but rather that it has to do with operators and generics. I think this build time regression, which is still in Xcode 10.2.1, needs some attention and priority.
cc @tkremenek