17701: diff(f,t) should work even with Function objects

src/sage/calculus/functional.py

@@ -125,7 +125,21 @@ def derivative(f, *args, **kwds):
         80*u^3*v^3
         sage: derivative(f, [u, v, v])
         80*u^3*v^3
+
+    Using function objects is possible::
+
+        sage: diff(sin,x)
+        cos(x)
+        sage: f = function('f')
+        sage: diff(f,x)
+        D[0](f)(x)
+        sage: _ = var("a,b,c")
+        sage: diff(f,a,b,c)
+        D[0, 1, 2](f)(a, b, c)
     """
+    from sage.symbolic.function import Function
+    if isinstance(f, Function):
+        f = f(*args)
     try:
         return f.derivative(*args, **kwds)
     except AttributeError:

src/sage/symbolic/integration/integral.py

@@ -580,7 +580,7 @@ def integrate(expression, v=None, a=None, b=None, algorithm=None, hold=False):
         sage: integrate(sin)
         Traceback (most recent call last):
         ...
-        TypeError
+        TypeError: Could not coerce into SR: "sin" of type <class 'sage.functions.trig.Function_sin'>
 
         sage: integrate(sin(x), x)
         -cos(x)

src/sage/symbolic/ring.pyx

@@ -285,7 +285,7 @@ cdef class SymbolicRing(CommutativeRing):
         elif isinstance(x, (RingElement, Matrix)):
             GEx_construct_pyobject(exp, x)
         else:
-            raise TypeError
+            raise TypeError('Could not coerce into SR: "{0}" of type {1}'.format(repr(x), type(x)))
 
         return new_Expression_from_GEx(self, exp)