D-Programming-Language/phobos — pull request #2463 by schuetzm (2014-08-25 19:17:07+00:00)
Title: std.typecons.Proxy needs to import std.traits.isArray

... because it is a mixin template which is evaluated at the place of
instantiation, where isArray is likely not available.

See here:
http://forum.dlang.org/thread/olvhztchmyxbedqmfanm@forum.dlang.org