firedrakeproject/firedrake — pull request #93 by wence- (2013-11-26 15:41:56+00:00)
Title: Raise error if trying to assemble on MFS + VFS

Assembling forms on MixedFunctionSpaces composed in part of a
VectorFunctionSpace is currently unimplemented so raise a useful error message
instead of going ahead and trying to build a kernel that does the wrong thing.