[swift-users] Request advice on closed range operator

[Peter van der Linden]

Hi,
I'm a swift novice, possibly asking an elementary question.
I noticed that in some cases, a closed range produces a compiler error 
message.

If you add whitespace before and after the closed range operator (in the 
example below), the error message goes away.
If you delete whitespace before and after the closed range operator, the 
error message also goes away.

If you have a space before the closed range operator, but not one after, 
you get an error message.
If you have a space after the closed range operator, but not one before, 
you get an error message.
Below is a small example that demonstrates the error.  Can anyone 
explain more about this?  I find it unusual that adding white space 
between two tokens can cause the compiler to emit an error message.   
Should I file a bug about this?

Thanks
   Peter

pvdl$ swift
Welcome to Apple Swift version 2.1.1 (swiftlang-700.1.101.15 
clang-700.1.81). Type :help for assistance.
   1>         let s1 = "foo"
   2.         let i = s1.startIndex
   3.         let j = s1.startIndex.advancedBy(1)
s1: String = "foo"
i: Index = {
   _base = {
     _position = 0
     _core = {
       _baseAddress = 0x000000010054d680
       _countAndFlags = 3
       _owner = nil
     }
   }
   _lengthUTF16 = 1
}
j: Index = {
   _base = {
     _position = 1
     _core = {
       _baseAddress = 0x000000010054d680
       _countAndFlags = 3
       _owner = nil
     }
   }
   _lengthUTF16 = 1
}
   4> var s2 = s1[ i ...j ]
repl.swift:4:16: error: expected ',' separator
var s2 = s1[ i ...j ]
                ^
               ,

   4>         var s2 = s1[ i...j ]
s2: String = "fo"
   5>         var s3 = s1[ i... j ]
repl.swift:5:27: error: expected ',' separator
         var s3 = s1[ i... j ]
                           ^
                          ,