Make Compile Fail on Non-Exhaustive Match in SBT

You can add -Xfatal-warnings to Scalac's options. That way any warning will be treated as an error.

In sbt, you can achieve that with:

scalacOptions += "-Xfatal-warnings"

Since scalac 2.13.2 there's a fairly granular control of warnings. To get what OP asks:

scalacOptions += "-Wconf:cat=other-match-analysis:error"

Detailed howto by Lukas Rytz.