Why do two distinct array literals equal each other in Swift?

Question

Why does the expression

import Foundation
["a", "b", "c"] == ["c", "b", "a"]

evaluate to true in a Swift playground?

(The expression evaluates to false when Foundation is not imported.)

Answer 1

Josh's answer is close, but not quite right. Option-click on the equals operator. Your literals are Foundation.CharacterSets.

public static func == (lhs: CharacterSet, rhs: CharacterSet) -> Bool

For literal resolution, the compiler is going to search

1. The module you're working in.
2. Your imports.
3. The Swift standard library. (Which has some special module-scope-disambiguation rule where implicitly-typed literals are Arrays, because that makes working with the language easier for the most part.)

Is this a bug of ambiguity? Yes. Is it resolvable? I doubt it. I bet it's broken because nobody has been able to get the performance to be good enough if it did an exhaustive search. But please, log a bug, find out, and report back!