Moved toOpenArray above its usage

ranges/typedranges.nim

@@ -132,10 +132,12 @@ proc `[]=`*[T, U, V](r: MutRange[T], s: HSlice[U, V], v: openarray[T]) =
   else:
     raise newException(RangeError, "different lengths for slice assignment")
 
+template toOpenArray*[T](r: Range[T]): auto =
+  # TODO: Casting through an {.unchecked.} array would be more appropriate
+  # here, but currently this results in internal compiler error.
+  toOpenArray(cast[ptr array[10000000, T]](r.start)[], 0, r.high)
+
 proc `[]=`*[T, U, V](r: MutRange[T], s: HSlice[U, V], v: Range[T]) {.inline.} =
   r[s] = toOpenArray(v)
 
 proc baseAddr*[T](r: Range[T]): ptr T {.inline.} = r.start
-
-template toOpenArray*[T](r: Range[T]): auto =
-  toOpenArray(cast[ptr array[10000000, T]](r.start)[], 0, r.high)

tests/ttypedranges.nim

@@ -13,3 +13,9 @@ suite "Typed ranges":
     var s = newSeq[int]()
     for a in r: s.add(a)
     check s == @[1, 2, 3, 4, 5]
+
+  test "subrange":
+    var a = newRange[int](5)
+    let b = toRange(@[1, 2, 3])
+    a[1 .. 3] = b
+    check a.toSeq == @[0, 1, 2, 3, 0]