Index: lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
===================================================================
--- lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
+++ lib/StaticAnalyzer/Core/SimpleConstraintManager.cpp
@@ -64,8 +64,12 @@
   }
 
   switch (Cond.getSubKind()) {
-  default:
-    llvm_unreachable("'Assume' not implemented for this NonLoc");
+  default: {
+    SmallString<64> buf;
+    llvm::raw_svector_ostream out(buf);
+    out << "'Assume' not implemented for this NonLoc: " << Cond << "\n";
+    llvm_unreachable(out.str().data());
+  }
 
   case nonloc::SymbolValKind: {
     nonloc::SymbolVal SV = Cond.castAs<nonloc::SymbolVal>();