Swift can't decide if [String] is Equatable?

gistfile1.swift

import XCTest

class GenericThing<T: Equatable> {
    func foo(t: T) {
        NSLog("foo \(t)")
    }
}

func genericFunc<T: Equatable>(left: T, right: T) {
    NSLog("\(left) == \(right) ?: \(left == right)")
}

class GenericThingTest {
      // WHY DOES THIS NOT COMPILE?!?
      //let testObject = GenericThing<[String]>()

    func testThatShouldClearlyPass() {
        // BUT THIS DOES???
        genericFunc(["foo"], ["foo"])
        XCTAssert(true)
    }
}