以下是此在线课程https://softwarefoundations.cis.upenn.edu/plf-current/StlcProp.html#lab222中出现的证明.
Proof with eauto.
remember (@empty ty) as Gamma.
intros t t' T HT. generalize dependent t'.
induction HT;
intros t' HE; subst Gamma; subst;
try solve [inversion HE; subst; auto].
- (* T_App *)
inversion HE; subst...
(* Most of the cases are immediate by induction,
and [eauto] takes care of them *)
+ (* ST_AppAbs *)
apply substitution_preserves_typing with T11...
inversion HT1...
Qed.
椭圆在这一行中做了什么？
apply substitution_preserves_typing with T11...