trace added in a failing invocation of auto :-(

diff --git a/matita/matita/contribs/lambdadelta/basic_2/unwind/sstas.ma b/matita/matita/contribs/lambdadelta/basic_2/unwind/sstas.ma
index c504e4edc1dfd5fbf99745a33b82ade43434e1ac..93e63853f520e2c15b0bd37831ad08032269d87f 100644 (file)
--- a/matita/matita/contribs/lambdadelta/basic_2/unwind/sstas.ma
+++ b/matita/matita/contribs/lambdadelta/basic_2/unwind/sstas.ma
@@ -48,7 +48,7 @@ qed-.
 (* Basic properties *********************************************************)
 
 lemma ssta_sstas: ∀h,g,L,T,U,l. ⦃h, L⦄ ⊢ T •[g, l+1] U → ⦃h, L⦄ ⊢ T •*[g] U.
-/3 width=2/ qed.
+/3 width=2 by R_to_star, ex_intro/ qed. (**) (* auto fails without trace *)
 
 lemma sstas_strap1: ∀h,g,L,T1,T2,U2,l. ⦃h, L⦄ ⊢ T1 •*[g] T2 → ⦃h, L⦄ ⊢ T2 •[g,l+1] U2 →
                     ⦃h, L⦄ ⊢ T1 •*[g] U2.