mathlib

a0b6bab2 - split(logic/nonempty): Split off `logic.basic` (#10762)

split(logic/nonempty): Split off `logic.basic` (#10762) This moves the lemmas about `nonempty` to a new file `logic.basic` I'm crediting Johannes for 79483182abffcac3a1ddd7098d47a475e75a5ed2