Swift: Tests for Substring.

Author: geoffw0

swift/ql/test/library-tests/dataflow/taint/libraries/string.swift

@@ -648,3 +648,32 @@ func furtherTaintThroughCallbacks() {
   let result6 = try? tainted.withContiguousStorageIfAvailable(callbackWithTaintedPointer)
   sink(arg: result6!) // $ tainted=612
 }
+
+func testSubstringMembers() {
+  let clean = ""
+  let tainted = source2()
+
+  let sub1 = tainted[..<tainted.index(tainted.endIndex, offsetBy: -5)]
+  sink(arg: sub1) // $ tainted=654
+  sink(arg: sub1.base) // $ MISSING: tainted=
+  sink(arg: sub1.utf8) // $ MISSING: tainted=
+  sink(arg: sub1.capitalized) // $ tainted=654
+  sink(arg: sub1.description) // $ tainted=654
+
+  var sub2 = tainted[tainted.index(tainted.startIndex, offsetBy: 5)...]
+  sink(arg: sub2) // $ tainted=654
+  let result1 = sub2.withUTF8({
+    buffer in
+    sink(arg: buffer[0]) // $ MISSING: tainted=
+    return source()
+  })
+  sink(arg: result1) // $ MISSING: tainted=
+
+  let sub3 = Substring(sub2.utf8)
+  sink(arg: sub3) // $ MISSING: tainted=
+
+  var sub4 = clean.prefix(10)
+  sink(arg: sub4)
+  sub4.replaceSubrange(..<clean.endIndex, with: sub1)
+  sink(arg: sub4) // $ MISSING: tainted=
+}