I found an online Swift Playground, and here is a smaller test case that produces the "unable to type-check this expression in reasonable time" message:
print("a" + "b" + "c" + 11 + "d")
...if you reduce it even further to:
print("a" + "b" + "c" + 11)
...the error message is:
<stdin>:3:23: error: binary operator '+' cannot be applied to operands of type 'String' and 'Int'
print("a" + "b" + "c" + 11)
~~~~~~~~~~~~~~~ ^ ~~
<stdin>:3:23: note: overloads for '+' exist with these partially matching parameter lists: (Int, Int), (String, String)
...it still falls down on with the "reasonable time" error on this tiny example, even if you fully specify the types:
let a:String = "a"
let b:String = "b"
let c:String = "c"
let d:String = "d"
let e:String = "e"
let n:Int = 11
print(a + b + c + n + d + e)
...is that pointing to a problem with type-checking or overload resolution more than type inference? Is there a way in Swift to annotate the types of sub-expressions in-line, so you could try something like:
The slow-down here isn't just from picking the correct `+` overloads, but also the various types that `"a"` could be (e.g. `String`, `Substring`, `Character`, or something like a `SQLQuery` type, depending on what libraries you have imported)
let a:String = "a" as String
let b:String = "b" as String
let c:String = "c" as String
let d:String = "d" as String
let e:String = "e" as String
let n:Int = 11 as Int
print((a + b + c) + n + d + e)
...has the long timeout, while:
let a:String = "a" as String
let b:String = "b" as String
let c:String = "c" as String
let d:String = "d" as String
let e:String = "e" as String
let n:Int = 11 as Int
print((a + b + c) as String + n + d + e)
