Error in testing whether a scalar field belongs to a module of differential forms

[egourgoulhon]

In Sage 8.8.beta1, as well as in Sage 8.6 and 8.7, we have

sage: M = Manifold(2, 'M')
sage: X.<x,y> = M.chart()
sage: f = M.scalar_field(x)
sage: f in M.diff_form_module(0)  # OK
True
sage: f in M.diff_form_module(1)  # Bang!
...
AttributeError: 'list' object has no attribute '_sage_'

Full log is attached.

CC: @DeRhamSource

Component: geometry

Keywords: differential forms

Author: Eric Gourgoulhon

Branch/Commit: df21950

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/27658

[egourgoulhon]

Description changed:

--- 
+++ 
@@ -10,3 +10,4 @@
 ...
 AttributeError: 'list' object has no attribute '_sage_'
 ```
+Full log is attached.

[egourgoulhon]

comment:1

Attachment: error.log

[egourgoulhon]

comment:3

Please review.

---

New commits:

d97d665

Fix coercion of scalar fields in modules of differential forms (trac #27658)

[egourgoulhon]

Branch: public/manifolds/fix_bug_27658

[egourgoulhon]

Commit: d97d665

[tscrim]

comment:4

#27658 -> :trac:`27658` and author name => positive review.

[tscrim]

Reviewer: Travis Scrimshaw

[sagetrac-git]

Changed commit from d97d665 to df21950

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

df21950

Fix reference to Trac ticket in doctest