Added $ for openarrays. Fixes #7940.

lib/system.nim

@@ -3443,6 +3443,14 @@ when not defined(nimNoArrayToString):
     ## generic ``$`` operator for arrays that is lifted from the components
     collectionToString(x, "[", ", ", "]")
 
+proc `$`*[T](x: openarray[T]): string =
+  ## generic ``$`` operator for openarrays that is lifted from the components
+  ## of `x`. Example:
+  ##
+  ## .. code-block:: nim
+  ##   $(@[23, 45].toOpenArray(0, 1)) == "[23, 45]"
+  collectionToString(x, "[", ", ", "]")
+
 proc quit*(errormsg: string, errorcode = QuitFailure) {.noReturn.} =
   ## a shorthand for ``echo(errormsg); quit(errorcode)``.
   echo(errormsg)

tests/system/toString.nim

@@ -6,6 +6,7 @@ doAssert "@[23, 45]" == $(@[23, 45])
 doAssert "[32, 45]" == $([32, 45])
 doAssert """@["", "foo", "bar"]""" == $(@["", "foo", "bar"])
 doAssert """["", "foo", "bar"]""" ==  $(["", "foo", "bar"])
+doAssert """["", "foo", "bar"]""" ==  $(@["", "foo", "bar"].toOpenArray(0, 2))
 
 # bug #2395
 let alphaSet: set[char] = {'a'..'c'}