Track assignment and invocation within attribute chains more thoroughly.
Record assignments affecting the whole attribute chain, not just immediate
assignments.
1a=4 2 3deff(x): 4defg(y,x=x): 5defh(a,z,x=x,y=y): 6returnx,y,z,a# parameter a overrides global scope 7returnh 8returng 9 10result=f(1)(2)(5,3) 11assertresult==(1,2,3,5)