 
 import Swift
 import StdlibUnittest
+
+#if _runtime(_ObjC)
+// FIXME: Foundation leaks through StdlibUnittest.  It adds some conformances
+// that overload resolution picks up in this code.
+import Foundation
+#endif
 
 
 // CHECK: testing...

  
  expectEqual(
    String.UTF8Index(abc.startIndex, within: abc.utf8).successor(),
    String.UTF8Index(abc.successor(abc.startIndex), within: abc.utf8))

  let diverseCharacters = summer + winter + winter + summer
  let s = diverseCharacters.unicodeScalars

  // Test all valid subranges si0..<si1 of positions in s.  ds is
  // always si0.distance(to: si1)
  for si0 in s.indices {
    for (ds, si1) in s.indices[si0..<s.endIndex].enumerated() {
      
      // Map those unicode scalar indices into utf8 indices
      let u8i1 = si1.samePosition(in: u8)
