Add test case for leak fixed by my SILGenPattern work.

The problem here was that we were performing a copy_on_success and then not
destroying that copy. We now do destroy that copy on master. This test will make
sure that we do not regress.

rdar://43076139

Author: gottesmm

test/Interpreter/patternmatch_on_enum_protocol_leak.swift

@@ -0,0 +1,46 @@
+// RUN: %target-run-simple-swift
+
+// REQUIRES: executable_test
+
+import StdlibUnittest
+
+// Make sure that in the following code we do not leak the case of the enum.
+
+protocol MyProtocol {}
+
+// An enum that wraps LeakingClass
+enum LeakingEnum1: MyProtocol {
+case eNone1
+case eLeakingClass1(LifetimeTracked)
+}
+
+// An enum that wraps LeakingClass
+enum LeakingEnum2 : MyProtocol {
+case eNone2
+case eLeakingClass2(LifetimeTracked)
+}
+
+var Tests = TestSuite("patternmatch_on_enum_protocol_leak")
+
+Tests.test("dontLeak") {
+  do {
+    let leakingClass = LifetimeTracked(0)
+    let leakEnum = LeakingEnum1.eLeakingClass1(leakingClass)
+    let control: MyProtocol = leakEnum
+
+    // This switch case order, interleaving LeakingEnum1 and LeakingEnum2 cases triggers the leak.
+    switch control
+    {
+    case LeakingEnum1.eNone1:               break
+    case LeakingEnum2.eNone2:               break
+
+    case LeakingEnum1.eLeakingClass1:       break
+    case LeakingEnum2.eLeakingClass2:       break
+
+    default:                                break
+    }
+  }
+  expectEqual(0, LifetimeTracked.instances)
+}
+
+runAllTests()