Description
| Previous ID | SR-4207 |
| Radar | rdar://23427259 |
| Original Reporter | @natecook1000 |
| Type | Bug |
| Status | Resolved |
| Resolution | Done |
Environment
Xcode 8.3b2
Additional Detail from JIRA
| Votes | 0 |
| Component/s | Compiler |
| Labels | Bug |
| Assignee | @slavapestov |
| Priority | Medium |
md5: 74d9820b2f361986d6c62b6fcddc6c05
is duplicated by:
- SR-9221 Superfluous senseless diagnostic on unsupported constrained extension of generic type
Issue Description:
You can currently write a generic function that uses a same-type constraint with an associated type and a protocol with a Self requirement, which typically can only be used as a constraint, not as a type. This can lead to some strange behavior:
func foo<S: Sequence where S.Iterator.Element == Equatable>(_ s: S) {
var iterator = s.makeIterator()
let x = iterator.next()!
// let y: Equatable = iterator.next()!
}Inside foo(_:), x is statically typed as Equatable, which you normally can't make happen. If you uncomment the line that declares y, which doesn't rely on type inference, you rightly get an error. foo(_:) isn't actually callable, since the same limitations prevent you from actually creating a sequence whose elements have the type Equatable, but the compiler should give an error when writing this function--the author almost certainly means to use the protocol in a "conforms to" relationship.