I'm trying to use Károly Lőrentey's B-tree based OrderedSet
in a project. However, I'm running into an issue where I can't declare an unqualified OrderedSet<T>
because the name conflicts between Foundation's NSOrderedSet
(imported as OrderedSet
in Swift 3) and BTree
's OrderedSet
.
let set = OrderedSet<Int>() // error: 'OrderedSet' is ambiguous for type lookup in this context // Found this candidate: Foundation.OrderedSet:3:14 // Found this candidate: BTree.OrderedSet:12:15
To resolve this conflict, you would normally qualify the name, and that would give you BTree.OrderedSet<T>
. However, the BTree
module also contains a class named BTree
. If I write BTree.OrderedSet
, Swift thinks that I'm referring to a type named OrderedSet
that is nested in the BTree.BTree
type.
let set = BTree.OrderedSet<Int>() // error: reference to generic type 'BTree' requires arguments in <...>
If I don't import BTree
, I can't use the BTree
name at all.
// no import BTree let set = BTree.OrderedSet<Int>() // error: use of undeclared type 'BTree'
How can I resolve this ambiguity between the BTree
type and the BTree
module?
The type can be disambiguated using the little-known import (class|struct|func|protocol|enum) Module.Symbol
syntax.
import struct BTree.OrderedSet
From this point on, OrderedSet unambiguously refers to the one in BTree.
If this would still be ambiguous or sub-optimal in some files, you can create a Swift file to rename imports using typealiases:
// a.swift import struct BTree.OrderedSet typealias BTreeOrderedSet<T> = BTree.OrderedSet<T>
// b.swift let foo = OrderedSet<Int>() // from Foundation let bar = BTreeOrderedSet<Int>() // from BTree
There was a new syntax discussed for Swift 3, but it fell through.
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