No longer able to type check expressions with Xcode 10.2 (caused by new SIMD API?)

[Jens]

@Martin

Interestingly, version B (but not version A) fails to compile in Xcode 10.1 as well if an import simd is added to the program:

# Version B with `import simd`
$ time swiftc main.swift 
main.swift:26:24: error: the compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions
    return 2*(3*a - b) + (4*c - d) // Typechecks quickly if A but sloooow if B.
           ~~~~~~~~~~~~^~~~~~~~~~~

real	0m14.559s
user	0m13.381s
sys	0m1.093s

Thanks for running that program on Xcode 10.1 (and macOS 10.14.4), interesting!

That makes one wonder what the results would be on a machine with macOS 10.14.3.
That is: Is version B not slow when compiled with Xcode 10.1 on macOS 10.14.3?

Perhaps the slow down in type checking has something to do with parts of Swift being in the OS as of macOS 10.14.4?