Open Radar

 
Summary:
The Swift standard library is rife with generic types like T, U, C, and S. Due to the complexity of some of the declarations—I’ve seen some cases where the angle brackets are more than 70 characters apart—it’s often easy to forget what a given type means by the time you reach it. The standard library should instead favor longer names that better describe the type when viewed in isolation.

Steps to Reproduce:
1. Start typing join().
2. Forget what order the arguments go in.
3. Command-click to view the declaration.
4. Try to read the parameter list.

Expected Results:
The names of the types in the parameter list make it reasonably clear what each parameter’s type is—for instance, CollectionType and SequenceType, or even CollectionType and SequenceOfCollectionsType.

Actual Results:
The names of the types are C and S, which is briefer but more opaque.

Notes:
The specific convention I use here—CollectionType, for instance—might be rejected because it’s too similar to “Collection.Type”, but if so, please don’t throw out the baby with the bathwater. This is a case where brevity is hurting clarity.

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Engineering has determined that this issue behaves as intended based on the following:

We don't think verbosity of the sort requested improves things at all:

func join<
  ExtensibleCollectionType : ExtensibleCollection, 
  SequenceType : Sequence where SequenceType.GeneratorType.Element == ExtensibleCollectionType>
(separator: ExtensibleCollectionType, elements: SequenceType) -> ExtensibleCollectionType

Naming things according to their role is arguably less-bad, but we still don't think it helps with overall readability.  Others may disagree; this is a judgement call.
 
func join<
  Separator : ExtensibleCollection, 
  Fragments : Sequence where Fragments.GeneratorType.Element == Separator>
(separator: Separator, fragments: Fragments) -> Separator

We are now closing this bug report.

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