as_vector and subfunctions broken

[Garth Wells]

The below UFL code breaks. The problem was introduced in changeset 941,

   http://bazaar.launchpad.net/~ufl-core/ufl/main/revision/941

element = VectorElement("Lagrange", triangle, 1)
scalar = FiniteElement("Lagrange", triangle, 1)
f = Coefficient(element)

# Works
#vs = Coefficient(scalar)
#v0 = as_vector([vs, 0.0, 0.0])
#L = dot(f, v0)*dx

# Breaks
v = TestFunction(element)
v0 = as_vector([v[0], 0.0, 0.0])
L = dot(f, v0)*dx

[Garth Wells (garth-wells)]

Looks like problem was introduced in

     ufl/algorithms/formtransformations.py

[Marie Rognes (meg-simula)]

This is the same issue as in Bug #676853