Wrong rewrite of a partial function passed to a symbolic operator

[OndrejSpanel]

Compiler version

3..4.1-RC2

Minimized code

Use -indent -rewrite on following code:

@main
def main: Unit = {

  object reactions {
    def += (f: PartialFunction[String, Unit]) = ???
  }

  reactions += {
    case a =>
    case b =>
  }
}

Output

@main
def main: Unit =

  object reactions:
    def += (f: PartialFunction[String, Unit]) = ???

  reactions += :
    case a =>
    case b =>

Compiling this results in following error:

C:\Dev\Sandbox\src\main\scala\Main.scala:7:16
expression expected but : found
reactions += :

Expectation

The output of "-indent", "-rewrite" should compile without errors

Note

This pattern is common when using Scala Swing.

[OndrejSpanel]

A similar pattern is also often seen in parser / combinators, where partial function follows ^^.

[LucySMartin]

I'm having a look at this. No promises, very new to this stuff, but I've reproduced and found a good looking spot to try some changes.

[LucySMartin]

I've raised #20043 - I think it fixes this