[swift-evolution] Fixing modules that contain a type with the same name

[Félix Cloutier]

Hello all,

I recently ran into a bug <http://stackoverflow.com/q/37892621/251153> that leaves me unable to fully-qualify the name of a type. If you import a module named Foo that also contains a type named Foo, attempts to fully-qualify any name in the Foo module will instead attempt to find something inside the Foo type. This bug has already been reported <https://bugs.swift.org/browse/SR-898>.

Here's an example with Károly Lőrentey's BTree module (which also contains a BTree type) that I encountered while trying to use the OrderedSet type:

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 solve this, you would normally write BTree.OrderedSet, but now Swift thinks that BTree is the BTree type, not the BTree module:

let set = BTree.OrderedSet<Int>()
// error: reference to generic type 'BTree' requires arguments in <...>
Any fix will require a change to the language, and as Jordan Rose stated on the bug, it "needs design", so I would like to bring up the issue and discuss possible solutions.

I can see several options (leaving "do nothing" aside, since I believe that this needs to be resolved):

Prevent modules from containing a type with the same name
Allow modules to be imported under different names (`import BTree as BTreeModule`, `import BTreeModule = BTree` or any similar syntax)
Create a new syntax that indicates that you're naming a module, not a type (like `_.BTree.OrderedSet`)

Thoughts?

Félix

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