Tweak tryParameterless to use readapt #24078

Original file line number	Diff line number	Diff line change
Expand Up		@@ -4274,16 +4274,15 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
		typr.println(i"adapt overloaded $ref with alternatives ${altDenots map (_.info)}%\n\n %")

		/** Search for an alternative that does not take parameters.
	* If there is one, return it, otherwise emit an error.
	* If there is one, return it, otherwise return the error tree.
		*/
		def tryParameterless(alts: List[TermRef])(error: => tpd.Tree): Tree =
		alts.filter(_.info.isParameterless) match
	case alt :: Nil => readaptSimplified(tree.withType(alt))
	case _ =>
	if altDenots.exists(_.info.paramInfoss == ListOfNil) then
	typed(untpd.Apply(untpd.TypedSplice(tree), Nil), pt, locked)
	else
	error
	case alt :: Nil => readaptSimplified(tree.withType(alt))
	case _ =>
	altDenots.find(_.info.paramInfoss == ListOfNil) match
	case Some(alt) => readaptSimplified(tree.withType(alt.symbol.denot.termRef))
	case _ => error

		def altRef(alt: SingleDenotation) = TermRef(ref.prefix, ref.name, alt)
		val alts = altDenots.map(altRef)
Expand Down Expand Up		@@ -4976,6 +4975,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
		case _ => NoType
		case _ => NoType

	// begin adapt1
		tree match {
		case _: MemberDef \| _: PackageDef \| _: Import \| _: WithoutTypeOrPos[?] \| _: Closure => tree
		case _ => tree.tpe.widen match {
Expand Down

32 changes: 32 additions & 0 deletions tests/neg/i21207.scala

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Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,32 @@

	abstract class P {
	def foo1(): Int = 1
	def foo2(x: Int): Int = 22
	def g4(s: String): String = s * 4
	}

	class C extends P {
	def foo1(x: Int): Int = 11
	def foo2(): Int = 2

	def foo3(): Int = 3
	def foo3(x: Int): Int = 33

	def g4(): Int = 4
	}

	object Test extends App {
	val c = new C
	println(c.foo1) // error was omitted because of nullary fallback during ambiguous overload resolution
	println(c.foo2) // error, add parens
	println(c.foo3) // error
	println(c.g4) // error
	val s: String = c.g4 // error missing arg, expected type picks method
	println(s)
	}

	/* Scala 2 warns for all three selections:
	warning: Auto-application to `()` is deprecated. Supply the empty argument list `()` explicitly to invoke method foo1,
	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. [quickfixable]
	*/

8 changes: 8 additions & 0 deletions tests/warn/i21207/Over.java

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Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,8 @@

	interface I {
	default int f() { return 42; }
	}

	public class Over implements I {
	public int f(int i) { return 42 + i; }
	}

17 changes: 17 additions & 0 deletions tests/warn/i21207/usage.scala

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Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,17 @@
	//> using options -source:3.0-migration

	// Hope to see a migration warning! with quickfix.

	class P {
	def g(): Int = 42
	}
	class C extends P {
	def g(i: Int): Int = 42 + i
	}

	object Test extends App {
	val over = Over()
	println(over.f) // nowarn Java
	val c = C()
	println(c.g) // warn migration
	}

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