Add test for ROOT-10689.

test/CodeGeneration/Lambda.C

@@ -0,0 +1,21 @@
+//------------------------------------------------------------------------------
+// CLING - the C++ LLVM-based InterpreterG :)
+//
+// This file is dual-licensed: you can choose to license it under the University
+// of Illinois Open Source License or the GNU Lesser General Public License. See
+// LICENSE.TXT for details.
+//------------------------------------------------------------------------------
+
+// RUN: cat %s | %cling | FileCheck %s
+
+// Check that lambda mangling is stable across transactions (ROOT-10689)
+
+.rawInput 1
+extern "C" int printf(const char*,...);
+template <class F> void call(F &f) { f(); }
+auto l1 = []() -> int { printf("ONE\n"); return 42; }; auto l2 = []() -> long { printf("TWO\n"); return 17; };
+.rawInput 0
+call(l1); call(l2); // CHECK: ONE
+// CHECK-NEXT: TWO
+call(l2);
+// CHECK-NEXT: TWO