bus error when trying to construct a piecewise discontinuous Fun

check this simple example:

using ApproxFun
d = PiecewiseSegment([-1,0,1.])
i = Fun(d) # identity
abs(i), sign(i) # work
Fun(sign, d) # crashes Julia with Bus error: 10

(i should not also that there is almost no documentation of PiecewiseSegment. is this not supposed to be used? i would in fact need it in my actual problem, in order to implement fast interpolation and integration of piecewise defined functions with known locations of discontinuities)

Start by running the provided PiecewiseSegment and Fun example to reproduce the bus error, then inspect the PiecewiseSegment and discontinuous Fun construction paths. Done means the example no longer crashes Julia and the piecewise sign function can be constructed; the payload names no files or tests to run.