struct of structs via ext mapper(was Re: [Swift-user] single structs for ext mapper.)

[Ben Clifford]

looks like its trying to map a path for the out structure itself, which 
probably shouldn't be happening.

as a workaround you might try adding a made-up filename for out itself, 
in addition to the members of out. no idea if that will work or not but 
worth a try.

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