Derivative is incorrectly set to 0 for some summation expressions.

[BodeTobias]

While experimenting with symbolic derivation by matrices, I came across the following strange behavior. Do I need a special function to sum up two expressions or is it a bug?

Code

import sympy as sym
sym.init_printing()

E = sym.MatrixSymbol('E', 3, 3)

print((sym.Trace(E)**2 + 0).diff(E))
print((sym.Trace(E)**2 + 1).diff(E))

Output

(2*Trace(E))*I
0

[oscarbenjamin]

More simply:

In [7]: E = MatrixSymbol('E', 3, 3)

In [8]: Trace(E).diff(E)
Out[8]: 𝕀

In [9]: (Trace(E) + 1).diff(E)
Out[9]: 𝟘

[sylee957]

I found some difference in results of Derivative(Trace(E) + 1, E).doit() and ArrayDerivative(Trace(E) + 1, E).doit(), so that may be able to point out some bug in the implementation.