So I got a report from an user saying that when pursuit is used against a ditto impersonating gengar, does not display the super effective message. Tested this in the simulator and the result is below. This is the screenshot. Probably in-game testing is required for this.
well this shouldn't be happening :v looks like it's a thing with BattleSituation::sendBack where the transformed mon is changed back to its regular form before the pursuit check is called so if like a mew on PO transformed into a non dark-weak mon it will still take SE pursuit damage on switching
Fuzzysqurl sent out Ditto! Fuzzysqurl2 sent out Gengar! The foe's Ditto transformed into Gengar! Start of turn 1 The foe's Ditto is being sent back! Gengar used Pursuit! It's super effective! The foe's Ditto lost 56% of its health! [...] The foe's Ditto transformed into Gengar! Start of turn 7 The foe's Ditto is being sent back! Gengar used Pursuit! It's super effective! The foe's Ditto lost 43% of its health! The foe's Ditto fainted! Fixed. And confirmed nothing breaks if the pokemon is KOed by pursuit. It still changes to its original form properly.