open tactic

example (a : nat) : a = a :=
by do
   define "x" (expr.const "nat" []),
   trace "---- after assert ----",
   trace_state,
   focus (do trace "--- inside focus tac ---", trace_state), -- SHOULD FAIL HERE
   trace "---- after focus tac ----",
   trace_state,
   x ← get_local "x",
   mk_app ("eq" <.> "refl") [x] >>= exact,
   return ()


definition tst2 (a : nat) : a = a :=
by do
   define "x" (expr.const "nat" []),
   trace "---- after assert ----",
   trace_state,
   focus (do trace "--- inside focus tac ---", trace_state, assumption),
   trace "---- after focus tac ----",
   trace_state,
   x ← get_local "x",
   mk_app ("eq" <.> "refl") [x] >>= exact,
   return ()