Add FrozenError#receiver

Similar to NameError#receiver, this returns the object on which
the modification was attempted.  This is useful as it can pinpoint
exactly what is frozen.  In many cases when a FrozenError is
raised, you cannot determine from the context which object is
frozen that you attempted to modify.

Users of the current rb_error_frozen C function will have to switch
to using rb_error_frozen_object or the new rb_frozen_error_raise
in order to set the receiver of the FrozenError.

To allow the receiver to be set from Ruby, support an optional
second argument to FrozenError#initialize.

Implements [Feature #15751]

1 files changed, 1 insertions, 1 deletions

diff --git a/eval.c b/eval.c
index 48473c79e2..e778d074dd 100644
--- a/eval.c
+++ b/eval.c
@@ -454,7 +454,7 @@ rb_class_modify_check(VALUE klass)
 		goto noclass;
 	    }
 	}
-	rb_error_frozen(desc);
+	rb_frozen_error_raise(klass, "can't modify frozen %s", desc);
     }
 }