Method dispatch error for show(io, ::UnionType)?

[rened]

A git bisect is pointing to 14bb4c2 as the source of the following error, where show(io, x::DataType) is invoked for an x of type UnionType, although a show(io, ::UnionType) exists:

Pkg.add("Images")
Pkg.checkout("Images")
Pkg.test("Images")
INFO: Computing test dependencies for Images...
INFO: No packages to install, update or removeINFO: Testing Images
Warning: New definition
    convert(Type{Images.Image{Cdest<:ERROR: LoadError: LoadError: LoadError: LoadError: type UnionType has no field name
 in show at show.jl:78
 in show at expr.jl:56
 in show at show.jl:83 (repeats 2 times)
 in include at ./boot.jl:252
 in include_from_node1 at ./loading.jl:133
 in include at ./boot.jl:252
 in include_from_node1 at ./loading.jl:133
 in reload_path at ./loading.jl:157
 in _require at ./loading.jl:69
 in require at ./loading.jl:52
 in include at ./boot.jl:252
 in include_from_node1 at ./loading.jl:133
 in include at ./boot.jl:252
 in include_from_node1 at loading.jl:133
 in process_options at ./client.jl:310
 in _start at ./client.jl:409
while loading /Users/rene/.julia/v0.4/Images/src/core.jl, in expression starting on line 246
while loading /Users/rene/.julia/v0.4/Images/src/Images.jl, in expression starting on line 35
while loading /Users/rene/.julia/v0.4/Images/test/colortypes.jl, in expression starting on line 1
while loading /Users/rene/.julia/v0.4/Images/test/runtests.jl, in expression starting on line 3