#16532: Weak morphism created with register_coercion can result in invalid
coercion
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Reporter: tscrim | Owner: tscrim
Type: defect | Status: new
Priority: critical | Milestone: sage-6.3
Component: coercion | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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First noted on #15475. Given `UniqueRepresentation` parents `A, B` and a
coercion `phi : A -> B` that was constructed/registered in the `__init__`
of `A` by using `register_coercion`. Next suppose that `B` becomes garbage
collected, and then so does `phi`. Then `B` is recreated. Expecting there
to be a coercion map from `A -> B`, the user becomes very surprised when
Sage responds with an errors saying there is no coercion map.
Right now I'm too tired to come up with a minimal example, but is this a
case of misuse or should we have morphisms passed to `register_coercion`
carry strong references? Other ideas?
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Ticket URL: <http://trac.sagemath.org/ticket/16532>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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