symbolic bridge tries to apply chain rule to index values

[kpeeters]

{x,y,z}::Coordinate;
{i,j,k}::Indices(values={x,y,z});
\partial{#}::PartialDerivative;
F_{i j}::Depends(x,y,z);
ex:=\partial_{i}{F_{i k}} + m**2 A_{k};
evaluate(ex);

produces an output which contains chain rule expression of the type Derivative(DN(x), x) because the indices get passed along as arguments.

[kpeeters]

Fixed by 2d8a0e4