[isabelle-dev] jEdit: Inconsistent behaviour with skipped by-proofs

[Makarius]

On Mon, 3 Dec 2012, Makarius wrote:

> On Tue, 13 Nov 2012, Lars Noschinski wrote:
>
>> Hi,
>> 
>> sometimes, I am encountering some erraneous behaviour of qed when a 
>> structured proof contains some facts for which the final "by" step failed.
>> 
>> Before the closing block the output buffer reads:
>>
>>   goal:
>>   No subgoals!
>> 
>> But qed then fails with an error message:
>> 
>> Failed to finish proof:
>> goal (4 subgoals):
>> {(x, w), (y, w), (w, x), (w, y)} ⊆ edges sG
>>  1. (x, w) ∈ edges (Abs_graph (insert w (verts G), insert (x, w) (insert 
>> (w, x) (insert (w, y) (insert (y, w) (edges G - {(x, y), (y, x)})))), fst, 
>> snd))
>>  2. (y, w) ∈ edges (Abs_graph (insert w (verts G), insert (x, w) (insert 
>> (w, x) (insert (w, y) (insert (y, w) (edges G - {(x, y), (y, x)})))), fst, 
>> snd))
>>  3. (w, x) ∈ edges (Abs_graph (insert w (verts G), insert (x, w) (insert 
>> (w, x) (insert (w, y) (insert (y, w) (edges G - {(x, y), (y, x)})))), fst, 
>> snd))
>>  4. (w, y) ∈ edges (Abs_graph (insert w (verts G), insert (x, w) (insert 
>> (w, x) (insert (w, y) (insert (y, w) (edges G - {(x, y), (y, x)})))), fst, 
>> snd))
>> 
>> The subgoals in this message are the remaining goals of a failed qed-step 
>> earlier in this proof.
>
> This is probably an effect of the implicit propagation of exceptions 
> between task groups, which is essential in batch mode to get all 
> exceptions together in the end.  Here it gets in the way, because the 
> "hopping" of failures from one task to another duplicates them in the 
> document view.

I have made some iterations on it leading up to Isabelle/a7484a7b6c8a, so 
there is a chance that it works smoothly for the release.

There is some danger here of provoking odd effects, like loosing errors 
that are not officially identified by the position information of the 
document model.

Please keep an eye on it for the coming release.


 	Makarius