Hi:

From the source code of Index definition, it's simple.

But when I use the Cmd+Click to see the Index definition from xcode, it's totally different:

associatedtype Index : Comparable where Self.Index == Self.Indices.Element, Self.Indices.Element == Self.Indices.Index, Self.Indices.Index == Self.SubSequence.Index, Self.SubSequence.Index == Self.Indices.Indices.Element, Self.Indices.Indices.Element == Self.Indices.Indices.Index, Self.Indices.Indices.Index == Self.SubSequence.Indices.Element, Self.SubSequence.Indices.Element == Self.SubSequence.Indices.Index, Self.SubSequence.Indices.Index == Self.SubSequence.Indices.Indices.Element, Self.SubSequence.Indices.Indices.Element == Self.SubSequence.Indices.Indices.Index

I guess that the compiler should does something, but I can't find any clue from source code of Swift.

Can someone give me a hint？

Thanks！！！