swift - How to create Dictionary that can hold anything in Key? or all the possible type it capable to hold

Question

I want to create a Dictionary that does not limit the key type (like NSDictionary)

So I tried

var dict = Dictionary<Any, Int>()

and

var dict = Dictionary<AnyObject, Int>()

resulting

error: type 'Any' does not conform to protocol 'Hashable'
var dict = Dictionary<Any, Int>()
           ^
<REPL>:5:12: error: cannot convert the expression's type '<<error type>>' to type '$T1'
var dict = Dictionary<Any, Int>()
           ^~~~~~~~~~~~~~~~~~~~~~

OK, I will use Hashable

var dict = Dictionary<Hashable, Int>()

but

error: type 'Hashable' does not conform to protocol 'Equatable'
var dict = Dictionary<Hashable, Int>()
           ^
Swift.Equatable:2:8: note: '==' requirement refers to 'Self' type
  func ==(lhs: Self, rhs: Self) -> Bool
       ^
Swift.Hashable:1:10: note: type 'Hashable' does not conform to inherited protocol 'Equatable.Protocol'
protocol Hashable : Equatable
         ^
<REPL>:5:12: error: cannot convert the expression's type '<<error type>>' to type '$T1'
var dict = Dictionary<Hashable, Int>()
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~

So Hashable inherited from Equatable but it does not conform to Equatable??? I don't understand...

Anyway, keep trying

typealias KeyType = protocol<Hashable, Equatable> // KeyType is both Hashable and Equatable
var dict = Dictionary<KeyType, Int>() // now you happy?

with no luck

error: type 'KeyType' does not conform to protocol 'Equatable'
var dict = Dictionary<KeyType, Int>()
           ^
Swift.Equatable:2:8: note: '==' requirement refers to 'Self' type
  func ==(lhs: Self, rhs: Self) -> Bool
       ^
Swift.Hashable:1:10: note: type 'KeyType' does not conform to inherited protocol 'Equatable.Protocol'
protocol Hashable : Equatable
         ^
<REPL>:6:12: error: cannot convert the expression's type '<<error type>>' to type '$T1'
var dict = Dictionary<KeyType, Int>()
           ^~~~~~~~~~~~~~~~~~~~~~~~~~

I am so lost now, how can I make compiler happy with my code?

---

I want to use the dictionary like

var dict = Dictionary<Any, Int>()
dict[1] = 2
dict["key"] = 3
dict[SomeEnum.SomeValue] = 4

---

I know I can use Dictionary<NSObject, Int>, but it is not really what I want.

Answer 1

Swift 3 update

You can now use AnyHashable which is a type-erased hashable value, created exactly for scenarios like this:

var dict = Dictionary<AnyHashable, Int>()