D-Programming-Language/dmd — pull request #3365 by CyberShadow (2014-03-07 14:55:51+00:00)
Title: fix Issue 4757 - A forward reference error with return of inner defined struct

https://d.puremagic.com/issues/show_bug.cgi?id=4757

It looks like semantic3 of nested structs was done too eagerly. It appears to be redundant.