nullary methods(methods that take no arguments) that return lambdas depend on whether an empty pair of parens are used

[scabug]

This line compiles

class B{ def b  :(Char)=>Unit = ((c:Char) => ()) };  val f:(Char)=>Unit = new B().b

While this line wont

class B{ def b():(Char)=>Unit = ((c:Char) => ()) };  val f:(Char)=>Unit = new B().b

Because B.b will be thought to return a ()=> (Char)=> () instead of a (Char)=> (). This behavior is not present when the return types are not lambdas, and it is masked with the caller uses parens, as that executes the returned lambda, which then returns the expected one.

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-9327?orig=1
Reporter: mako yass (makoConstruct)
Affected Versions: 2.11.4, 2.11.6
Duplicates #7187

[som-snytt]

Fixed in the linked ticket, but life goes on and 2.13.8 warns

       warning: Auto-application to `()` is deprecated. Supply the empty argument list `()` explicitly to invoke method b,
       or remove the empty argument list from its definition (Java-defined methods are exempt).
       In Scala 3, an unapplied method like this will be eta-expanded into a function.