Scala Inliner and Optimizer | @lightbend

TL;DR Don’t enable the optimizer during development: it breaks incremental compilation, and it makes the compiler slower. Only enable it for testing, on CI, and to build releases. Enable method-local optimizations with -opt:l:method. This option is safe for binary compatibility, but typically doesn’t improve performance on its own. Enable inlining in addition to method-local optimizations with -op