@UlrikeFischer @DavidCarlisle I read your comments to Denis' question, and have a doubt. I knew one should not put arbitrary content through and `\edef`. However, I was never sure about what the L3 e- and x-type corresponded to. `interface3` says "Functions which are not “protected” are fully expanded inside an e-type or x-type
expansion. In contrast, “protected” functions are not expanded within e and x expansions." I took that as e and x expansions corresponded to `\protected@edef`. Is this a different meaning of "protected" there?