[Concepts] Fix ast dump for immediately declared constraint.

Reviewed By: nridge

Differential Revision: https://reviews.llvm.org/D84461
diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index 91b9848..5b6c608 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -1994,7 +1994,7 @@
       dumpBareDeclRef(TC->getFoundDecl());
       OS << ")";
     }
-    Visit(TC->getImmediatelyDeclaredConstraint());
+    AddChild([=] { Visit(TC->getImmediatelyDeclaredConstraint()); });
   } else if (D->wasDeclaredWithTypename())
     OS << " typename";
   else