Yeah, I think this behavior is deliberate, and it'd also be hard to do for non-literal types. (We'd need some kind of notion of structurally-equivalent expressions, which is not unreasonable but isn't something the compiler currently has.). @moiseev, @airspeedswift, thoughts?
Is including the same key in a dictionary literal a bug, and if so, can it be caught?
If the problem is in the name, which promises a dictionary literal (which this isn't due to key duplication), can it be solved by renaming to a more accurate `DictionaryStyleLiteral` or `DictionaryStyleTupleSequence` or `DictionaryStyleLiteralInitializable` sort of thing?