Win 7 x64
Broken in master build on 1/10/2015 (hash unknown)
Short description of error
When hiding parts of the scene with Alt+B to get to hard to reach areas, snapping still acts as if the invisible portions of the mesh are there. Makes Alt+B functionally useless for retopology, despite being one of the areas where it would be most useful.
Exact steps for others to reproduce the error
Hide part of a mesh with Alt+B where one part of the mesh would normally occlude another. Attempt to snap verts to only the visible portion of the mesh.