Dump more info before crashing.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 1ab9dd05258e425f46f1bf51d444096dedb6b7af..ff46fbfa70fdca4a158ef4ad7afe01569dab0700 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -6418,6 +6418,23 @@ bool Function::TestParameterType(
     Heap::Space space) const {
   AbstractType& other_param_type =
       AbstractType::Handle(other.ParameterTypeAt(other_parameter_position));
+
+  // TODO(regis): Remove this debugging code.
+  if (other_param_type.IsNull()) {
+    const Class& owner = Class::Handle(Owner());
+    const Class& other_owner = Class::Handle(other.Owner());
+    THR_Print("*** null other_param_type ***\n");
+    THR_Print("parameter_position: %" Pd "\n", parameter_position);
+    THR_Print("other_parameter_position: %" Pd "\n", other_parameter_position);
+    THR_Print("function: %s\n", ToCString());
+    THR_Print("function owner: %s\n", owner.ToCString());
+    THR_Print("other function: %s\n", other.ToCString());
+    THR_Print("other function owner: %s\n", other_owner.ToCString());
+    AbstractType& param_type =
+        AbstractType::Handle(ParameterTypeAt(parameter_position));
+    THR_Print("param_type: %s\n", param_type.ToCString());
+  }
+
   if (!other_param_type.IsInstantiated()) {
     other_param_type =
         other_param_type.InstantiateFrom(other_type_arguments,
@@ -6432,6 +6449,21 @@ bool Function::TestParameterType(
   }
   AbstractType& param_type =
       AbstractType::Handle(ParameterTypeAt(parameter_position));
+
+  // TODO(regis): Remove this debugging code.
+  if (param_type.IsNull()) {
+    const Class& owner = Class::Handle(Owner());
+    const Class& other_owner = Class::Handle(other.Owner());
+    THR_Print("*** null param_type ***\n");
+    THR_Print("parameter_position: %" Pd "\n", parameter_position);
+    THR_Print("other_parameter_position: %" Pd "\n", other_parameter_position);
+    THR_Print("function: %s\n", ToCString());
+    THR_Print("function owner: %s\n", owner.ToCString());
+    THR_Print("other function: %s\n", other.ToCString());
+    THR_Print("other function owner: %s\n", other_owner.ToCString());
+    THR_Print("other_param_type: %s\n", other_param_type.ToCString());
+  }
+
   if (!param_type.IsInstantiated()) {
     param_type = param_type.InstantiateFrom(type_arguments,
                                             bound_error,