[modersky]

It's currently about as fast as Scala 2.12, which means it compiles at roughly 3000 lines/sec. However, it supports more aggressive incremental compilation than Scala 2 so at least in my projects, which are typically 50K to 100K lines, most compiles are under a second, and I rarely see compile times over 5 seconds.

There's ongoing performance work to make both Scala 2 and Scala 3 faster than they are now. A lot of what people perceive as slow compile times are actually other factors (such as inefficient macros or slow build tools).

[jvican]

> However, it supports more aggressive incremental compilation than Scala 2

I'm not sure what you mean here... but Scala 2 and Dotty have the same incremental compiler, and their independent bridges feature overall the same quality (which is high and heavily battle tested, for those interested).

[modersky]

It has to do with what kind of dependencies the incremental compiler wrapper (e.g. zinc) can extract from the baseline compiler (e.g nsc or dotc). The Scala 3 compiler dotc handles that itself, which has the potential to achieve better accuracy. But I am not sure how much it matters in practice. We'll find out.

[jvican]

> which has the potential to achieve better accuracy

The quality of the used names extraction affects accuracy, but not compile speed. I must say, Dotty and Scala are extracting about the same amount of dependencies, with some corner cases being covered better in Dotty (for example, changes in constant values).

I don't see a way Dotty can become a faster incremental compiler that doesn't involve adding the incrementality in the compiler.

[Cyph0n]

I'm not sure if you noticed, but you are replying to the designer of Scala.

[JiminHsieh]

I think jvican noticed this. jvican is the engineer from Scala Center which is supported by EPFL.

Edit: typo

[Cyph0n]

Oh, my bad then haha!