Bug in tableaux.random_element

[BruceWestbury]

This gives a tableau of the correct shape but incorrect evaluation (aka weight)

sage: ST = SemistandardTableaux(shape=[4,4,4],eval=[1]*12)
sage: ST.cardinality()
462
sage: ST.random_element()
[[1, 4, 4, 5], [5, 5, 6, 6], [6, 11, 11, 12]]

CC: @tscrim @sagetrac-sage-combinat @simon-king-jena @nthiery

Component: combinatorics

Keywords: category framework, tableaux

Issue created by migration from https://trac.sagemath.org/ticket/25575

[darijgr]

comment:1

The problem is that sage.combinat.tableau.SemistandardTableaux_shape_weight inherits the random_element code from SemistandardTableaux_shape. We really need to talk about this issue, since it appears to be universal -- it's clear that if Parent X represents a subset of Parent Y, then the ElementClass of X should inherit from the ElementClass of Y, but it feels wrong that Parent X itself inherits from Parent Y. All sorts of other methods like _list_ and an_element can be equally affected by this.

[darijgr]

Changed keywords from none to category framework, tableaux