Index: lib/AST/ItaniumMangle.cpp
===================================================================
--- lib/AST/ItaniumMangle.cpp
+++ lib/AST/ItaniumMangle.cpp
@@ -4300,7 +4300,9 @@
   // Compute 'L'.
   // parmDepth does not include the declaring function prototype.
   // FunctionTypeDepth does account for that.
-  assert(parmDepth < FunctionTypeDepth.getDepth());
+  assert(parmDepth < FunctionTypeDepth.getDepth() ||
+         (parmDepth == FunctionTypeDepth.getDepth() &&
+          !FunctionTypeDepth.isInResultType()));
   unsigned nestingDepth = FunctionTypeDepth.getDepth() - parmDepth;
   if (FunctionTypeDepth.isInResultType())
     nestingDepth--;