Index: lib/ASTMatchers/ASTMatchFinder.cpp
===================================================================
--- lib/ASTMatchers/ASTMatchFinder.cpp
+++ lib/ASTMatchers/ASTMatchFinder.cpp
@@ -676,13 +676,17 @@
       //  c) there is a bug in the AST, and the node is not reachable
       // Usually the traversal scope is the whole AST, which precludes b.
       // Bugs are common enough that it's worthwhile asserting when we can.
-      assert((Node.get<TranslationUnitDecl>() ||
-              /* Traversal scope is limited if none of the bounds are the TU */
-              llvm::none_of(ActiveASTContext->getTraversalScope(),
-                            [](Decl *D) {
-                              return D->getKind() == Decl::TranslationUnit;
-                            })) &&
-             "Found node that is not in the complete parent map!");
+#ifndef NDEBUG
+      if (!Node.get<TranslationUnitDecl>() &&
+          /* Traversal scope is full AST if any of the bounds are the TU */
+          llvm::any_of(ActiveASTContext->getTraversalScope(), [](Decl *D) {
+            return D->getKind() == Decl::TranslationUnit;
+          })) {
+        llvm::errs() << "Tried to match orphan node:\n";
+        Node.dump(llvm::errs(), ActiveASTContext->getSourceManager());
+        llvm_unreachable("Parent map should be complete!");
+      }
+#endif
       return false;
     }
     if (Parents.size() == 1) {