Automatic Decoder derivation hangs when used across files about circe

[travisbrown]

This now compiles in seconds (in 0.8.0 and earlier). There are a lot of things that changed in #247 and I don't remember at the moment which pieces are most likely responsible for clearing this up, but I'm going to go ahead and close the issue since it's not a problem any more.

[travisbrown]

Hey @maxaf, sorry this issue slipped by me (I was camping when it arrived and somehow never noticed it). Feel free to bother me on Gitter or Twitter or here if I ever just let something sit for weeks.

The good news is that I just confirmed that I can reproduce this issue in 0.3.0 and that it's fixed in 0.4.0 (not head or the snapshot, which aren't updated yet, but I'm hoping to have the release out tonight).

[maxaf]

Thanks & no worries! I worked around the (still unknown to me) root cause by rearranging my compilation units. 0.4.0 looks awesome, looking forward to it!

Through a form of differential diagnosis I've pursued this issue and the general slowness of compiling any derived circe instances. The main insight was that compilation performance tanks when target directories are located on a slow file system. In my case this was a VirtualBox shared directory inside a Vagrant-managed VBox instance. I gained back more than 40% of compilation time by moving target directories to a faster file system by way of an sbt plugin.

Could you explain in a nutshell what the root cause of this issue was? I never thought that placing code in one file or another might affect anything apart from restrictions on deriving from a sealed type.