7a58da1181
eval_expr creates auxiliary definitions in the VM. These auxiliary definitions are gone after the VM finishes. We store vm_obj's in the attribute_manager. Before this commit, Lean was crashing in the following scenario: 1- A new caching_user_attribute is defined, and the user data structure contains closures. 2- The closures are created using eval_expr. 3- When reusing the cached values, the system crashes when trying to apply a closure created using eval_expr. The closure points to an auxiliary definition that has already been deleted. The new test exposes the problem. This is not a hypothetical scenario, the new test is based on the Lean - Mathematica integration being developed by @rlewis1988. The fix consists in making sure we do not cache anything if the VM environment has been updated by eval_expr. I believe this is acceptable behavior. eval_expr is a very low level tactic, and I don't see a good motivation for invoking it when constructing the cache. BTW, the test can be relaxed if the vm_attr does not contain closures. However, it doesn't seem to pay off. Another potential fix would be to propagate the definitions created by eval_expr to the main environment. However, I think this is not acceptable. We will be flooding the main environment with useless temporary definitions created by `eval_expr`. This commit also stores the environment at caching time, and make sure the cache is only reused if the current environment is a descendant of the the one at caching time. This is fixing a different potential bug.
26 lines
798 B
Text
26 lines
798 B
Text
open tactic
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meta def my_attr : caching_user_attribute (name → bool) :=
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{ name := "my_attr",
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descr := "my attr",
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mk_cache := λ ls, do {
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els ← list_name.to_expr ls,
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c ← to_expr `(λ n : name, (name.cases_on n ff (λ _ _, to_bool (n ∈ %%els)) (λ _ _, ff) : bool)),
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eval_expr (name → bool) c
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},
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dependencies := []
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}
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run_command attribute.register `my_attr
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meta def my_tac : tactic unit :=
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do f ← caching_user_attribute.get_cache my_attr,
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trace (f `foo),
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return ()
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@[my_attr] def bla := 10
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run_command my_tac
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@[my_attr] def foo := 10 -- Cache was invalided
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run_command my_tac -- Add closure to the cache containing auxiliary function created by eval_expr
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run_command my_tac -- Cache should be flushed since the auxiliary function is gone
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