from ngsolve import *
from netgen.occ import *

maxh = 0.1
outer = Circle((0.0, 0.0), 1).Face()
#geo = Glue([inner, mid, outer])

mesh = Mesh(OCCGeometry(outer, dim=2).GenerateMesh(maxh=maxh))
#mesh = Mesh(OCCGeometry(geo, dim=2).GenerateMesh(maxh=maxh))

fes = L2(mesh, order = 2)

v = fes.TestFunction()

f = CoefficientFunction(1)
f0 = CoefficientFunction(0)

F0 = GridFunction(fes)
F0.Set(f0)

LinearForm(f * v * dx) # Works, non-zero LinearForm
LinearForm(F0 * v * dx) # Works, zero LinearForm
LinearForm(f0 * v * dx) # Does not work
LinearForm(0 * v * dx) # Equivalent, does not work