Teach typedConstructorPattern to ignore non-redefining unapplies

In pos/t12250.scala Foo defines an unapply which doesn't redefine the
synthetic one.  Thus unapply is overloaded.  In the pattern being typed,
the synthetic one is indeed the one seeked, so despite being overloaded,
we should convertToCaseConstructor.

src/compiler/scala/tools/nsc/typechecker/PatternTypers.scala

@@ -97,9 +97,9 @@ trait PatternTypers {
       // Dueling test cases: pos/overloaded-unapply.scala, run/case-class-23.scala, pos/t5022.scala
       // A case class with 23+ params has no unapply method.
       // A case class constructor may be overloaded with unapply methods in the companion.
-      // A case class maybe have its own custom unapply (so non-synthetic) scala/bug#11252
-      // Unapply methods aren't `isCaseApplyOrUnapply` in Scala 3 tasty/run/src-2/tastytest/TestColour.scala
-      else if (canElide && caseClass.isCase && !member.isOverloaded && (member == NoSymbol || member.isSynthetic))
+      // A case class may have its own custom unapply (so non-synthetic) pos/t11252.scala
+      // A case class may have its own custom unapply unrelated to deconstructing pos/t12250.scala
+      else if (canElide && caseClass.isCase && (!member.isOverloaded && (member == NoSymbol || member.isSynthetic) || member.alternatives.exists(_.isSynthetic) && caseClass.tpe =:= pt))
         logResult(s"convertToCaseConstructor($fun, $caseClass, pt=$pt)")(convertToCaseConstructor(fun, caseClass, pt))
       else if (!reallyExists(member))
         CaseClassConstructorError(fun, s"${fun.symbol} is not a case class, nor does it have a valid unapply/unapplySeq member")

test/files/pos/t12250.scala

@@ -0,0 +1,11 @@
+// scalac: -Werror
+final case class Foo(value: String)
+
+object Foo {
+  def unapply(str: String): Option[Foo] = Some(Foo(str))
+
+  def extract(id: Foo): String =
+    id match {
+      case Foo(a) => a
+    }
+}