Allow implicit parameters in extractors

Author: mbovel

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -1581,7 +1581,7 @@ trait Applications extends Compatibility {
               val newAcc =
                 params match
                   case param :: _ if param.isType => true
-                  case param :: _ if param.isTerm && !param.isOneOf(GivenOrImplicit) => false
+                  case param :: _ if param.isTerm && !param.is(Given) => false
                   case _ => acc
               hasTrailingTypeParams(paramss.tail, newAcc)
 

tests/pos/i23499.scala

@@ -0,0 +1,18 @@
+def summonsTest =
+  given Type[String] = ???
+  val opt1: Option[Wrapper[String]] = Wrapper.unapply[String] // ok
+  val opt2 = Wrapper.unapply[String]
+  opt2.map(_.getValue)
+
+def patternMatchTest =
+  Type[String] match
+    case Wrapper(v) => v.getValue // was an error
+
+type Type[A] = Class[A] // any rhs would work here
+object Type:
+  def apply[A]: Type[A] = ???
+
+trait Wrapper[T]:
+  def getValue: T = ???
+object Wrapper:
+  def unapply[T](implicit ev: Type[T]): Option[Wrapper[T]] = None