[SR-2493] Escaping and Type-aliases don't work together

[swift-ci]

Previous ID	SR-2493
Radar	None
Original Reporter	chriseidhof (JIRA User)
Type	Bug
Status	Resolved
Resolution	Duplicate

Additional Detail from JIRA

Votes	0
Component/s
Labels	Bug
Assignee	None
Priority	Medium

md5: de270f0eb69ba2760e8b414045a431b4

duplicates:

• SR-2316 typealias for block type not defaulting to @NoEscape

Issue Description:

I created a typealias for a sort descriptor:

typealias SortDescriptor<A> = (A, A) -> Bool

Now, when I try to create function that takes a sort descriptor and inverts it, the parameter should be marked as escaping, however, the compiler doesn't detect that, and worse, disallows it:

func invert<A>(_ x: SortDescriptor<A>) -> SortDescriptor<A> {
return { l, r in !x(l, r)
}

If I define the same function without the typealias, all is well:

// Exact same function, but now it needs to be marked as escaping... (which is correct)
func invert2<A>(_ x: @escaping (A,A) -> Bool) -> (A,A) -> Bool {
return { l, r in !x(l, r)
}

I can, however, call the first function just fine:

let gte: SortDescriptor<Int> = invert(<)

[swift-ci]

Comment by Chris Eidhof (JIRA)

Sorry about the messed up code samples, I have no clue how to convince JIRA to display it preformatted... The triple braces somehow disappear

[swift-ci]

Comment by Chris Eidhof (JIRA)

Btw, the generics are not the issue here, it's the same when you have a non-generic typealias, e.g. (Int,Int) -> Bool.