[isabelle-dev] auto raises a TYPE exception

[Johannes Hölzl]

Hi,

In Isabelle2013 as well as the current development revision (#0a7b4e0384d0)
the following call to "auto" raises a TYPE exception in envir.ML

---- 8< ----
theory Scratch
  imports Main
begin

class test =
  fixes P :: "'a set ⇒ bool"

lemma
  shows P_UNIV [intro]: "P UNIV"
    and P_Int [intro]: "P S ⟹ P T ⟹ P (S ∩ T)"
    and P_Union [intro]: "∀S∈K. P S ⟹ P (⋃ K)"
    and P_INT [intro]: "finite A ⟹ ∀x∈A. P (B x) ⟹ P (⋂x∈A. B x)"
    sorry

lemma
  fixes Q :: "'b ⇒ bool" and f :: "'a::test ⇒ 'b"
  shows "(∃S. P S ∧ x ∈ S ∧ (∀xa∈S. Q (f xa)))"
  apply (auto simp only:)
  oops

------------

It looks like the problem is somewhere in the call to Classical.inst0_step_tac in nodup_depth_tac (clasimp.ML):

----  clasimp.ML  ----

fun nodup_depth_tac ctxt m i st =
  SELECT_GOAL
    (Classical.safe_steps_tac ctxt 1 THEN_ELSE
      (DEPTH_SOLVE (nodup_depth_tac ctxt m 1),
        Classical.inst0_step_tac ctxt 1 APPEND COND (K (m = 0)) no_tac
          (slow_step_tac' ctxt 1 THEN DEPTH_SOLVE (nodup_depth_tac ctxt (m - 1) 1)))) i st;

-----------------------

Dmitriy and I tried to simplify the testcase by replicating the goal on
which inst0_step_tac is called but could not replicated the failure.

* Has anybody a idea what is causing this exception?

* Any helpful tips how to continue to debug this bug?

* How can I activate backtraces in ML to get an better understand of the
problem? I tried declare [[ML_trace = true]] but I didn't get a
backtrace.


Greetings,
  Johannes