1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Section S. Variable A:Prop. Variable W:A. Remark T: A -> A. intro Z. rename W into Z_. rename Z into W. rename Z_ into Z. exact Z. Qed. (* bug : Error: Unbound reference: In environment A : Prop W : A Z : A The reference 2 is free *) End S.