raco: tdd commit for uwescience/myria-web#263
raco: tdd commit for uwescience/myria-web#263

Because of a bug in the type checking, we could accidentally traverse a binary tree in
exponential time instead of linear. The bug was checking the type of the same side
twice instead of checking both sides. This test should expose the bug, which
will be fixed later.

uwescience/raco,uwescience/raco,uwescience/raco,uwescience/raco,uwescience/raco