Can't `assemble` with `EquationBC` objects

[wence-]

It is not possible to assemble (at least a matrix) with EquationBC boundary conditions through the "front door" assemble interface:

from firedrake import *

mesh = UnitSquareMesh(2, 2)

V = FunctionSpace(mesh, "CG", 1)

u = TrialFunction(V)
v = TestFunction(V)

a = - dot(grad(v), grad(u)) * dx

g = Function(V).assign(1)
e2 = as_vector([0., 1.])
a1 = (-dot(grad(v), e2) * dot(grad(u), e2) + v * u) * ds(1)
L1 = Constant(0) * v * ds(1)
bbc = DirichletBC(V, g, ((1, 3), (1, 4)))
u = Function(V)
bc1 = EquationBC(a1 == L1, u, 1, bcs=[bbc])

assemble(a, bcs=bc1)
=> AttributeError: 'Matrix' object has no attribute 'dat'

assemble(a, bcs=[bc1])
=> AttributeError: 'EquationBC' object has no attribute 'integrals'

If one is not supposed to use equation bcs like this, we need a proper error. I notice this because I am refactoring assembly in preparation for insertion into mixed dats/matrices directly (as an option). The equation bcs stuff is such a rat's nest, I have no confidence in my correctness.

[ksagiyam]

Thanks. This one is now fixed here (waiting for Jenkins to complete):
https://github.com/firedrakeproject/firedrake/tree/fix_equation_bc