need protection against broken Isabelle rellization
The commit 8a7974cf broke the Isabelle realizations of set.Set and set.FSet. It should not have been accepted in master branch. We need to reinforce the protection against broken realizations
The commit 8a7974cf broke the Isabelle realizations of set.Set and set.FSet. It should not have been accepted in master branch. We need to reinforce the protection against broken realizations