lean4-htt/tests/lean/change2.lean

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open tactic nat expr option
attribute [simp]
lemma succ_eq_add (n : nat) : succ n = n + 0 + 1 :=
rfl
example (a b : nat) : a = b → succ (succ a) = succ (b + 1) :=
by do intro `Heq,
get_local `a >>= subst,
trace_state,
dsimp_target,
trace "---- after dsimp ----",
trace_state,
t ← target,
match (is_eq t) with
| (some (lhs, rhs)) := do pr ← mk_app `eq.refl [lhs], exact pr
| none := failed
end