Unions of subsets of a fixed open set X are not known to be subsets of X

[tscrim]

See the following:

sage: T = Manifold(2, 'T', start_index=1)
sage: U0 = T.open_subset("U0", latex_name="U_0")
sage: Uh = T.open_subset("Uh", latex_name="U_h")
sage: T.declare_union(U0, Uh)
sage: I0h = U0.intersection(Uh, name="I0h", latex_name="I_{0h}")
sage: X1 = I0h.open_subset('X1', "X_1")
sage: X2 = I0h.open_subset('X2', "X_2")
sage: X3 = I0h.open_subset('X3', "X_3")
sage: X1.union(X2).is_subset(I0h)
False

This means I cannot declare I0h as the union of 3 subsets.

CC: @egourgoulhon @mjungmath

Component: manifolds

Author: Eric Gourgoulhon

Branch/Commit: bbe5d11

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/30401

[egourgoulhon]

Commit: bbe5d11

[egourgoulhon]

New commits:

bbe5d11

Fix bug in union of manifold subsets (Trac #30401)

[egourgoulhon]

Branch: public/manifolds/union_subsets_30401

[egourgoulhon]

Author: Eric Gourgoulhon

[tscrim]

Reviewer: Travis Scrimshaw

[tscrim]

comment:3

Thank you.

[egourgoulhon]

comment:4

Thanks for having reported the bug and performed the review.

[vbraun]

Changed branch from public/manifolds/union_subsets_30401 to bbe5d11