Swift: Add taint test of try.

Author: geoffw0

swift/ql/test/library-tests/dataflow/taint/try.swift

@@ -0,0 +1,19 @@
+func clean() throws -> String { return ""; }
+func source() throws -> String { return ""; }
+func sink(arg: String) {}
+
+func taintThroughTry() {
+	do
+	{
+		sink(arg: try clean())
+		sink(arg: try source()) // tainted [NOT DETECTED]
+	} catch {
+		// ...
+	}
+
+	sink(arg: try! clean())
+	sink(arg: try! source()) // tainted [NOT DETECTED]
+
+	sink(arg: (try? clean())!)
+	sink(arg: (try? source())!) // tainted [NOT DETECTED]
+}