Do not rewrite { (a: Int) => ... } to { a: Int => ... }

[smarter]

The latter syntax is removed from Dotty due to its irregularity:

scala> def foo : Int => Int = { a: Int => a }
1 |def foo : Int => Int = { a: Int => a }
  |                         ^^^^^^
  |parentheses are required around the parameter of a lambda
  |This construct can be rewritten automatically under -language:Scala2 -rewrite.

[niktrop]

@smarter Thank you for the contribution, it will be included in the coming 2019.3 release. Please sign our contributor license agreement: https://www.jetbrains.com/agreements/cla/

I also created a ticket for the actual fix of deprecated syntax:
https://youtrack.jetbrains.com/issue/SCL-16540

[neko-kai]

@niktrop @smarter
This is a dotty-only change that hasn't went through a SIP yet and may well be reverted. I'd prefer to have an option to ignore the deprecation/rewrite.

[dwijnand]

You mean keep the rewrite? The deprecation you'll only see if you compile it with Dotty, so not a intellij-scala change.

[niktrop]

@neko-kai
Right now only warning for syntax with parentheses is removed. If we'll add an inspection for deprecated syntax without parentheses, it will be configurable.

[neko-kai]

@niktrop Got it, thank you! 👍
@dwijnand Yeah, that's what I mean

[SrTobi]

I created the inspection for SCL-16540 and turned it off by default for now. Is there an official link/github-issue for this change in dotty so I can put that into the Description of the inspection?

[smarter]

Is there an official link/github-issue for this change in dotty so I can put that into the Description of the inspection?

PR is scala/scala3#7156, it looks like we don't have a documentation page for that change currently.