Only evaluate transparent inline unapply once

Fixes scala#19369

Author: nicolasstucki

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

@@ -1446,7 +1446,9 @@ trait Applications extends Compatibility {
             unapplyArgType
 
         val dummyArg = dummyTreeOfType(ownType)
-        val unapplyApp = typedExpr(untpd.TypedSplice(Apply(unapplyFn, dummyArg :: Nil)))
+        val unapplyApp = withMode(Mode.NoInline) { // transparent inline unapplies are exapnded when indexing the pattern see `indexPattern` in Typer.
+          typedExpr(untpd.TypedSplice(Apply(unapplyFn, dummyArg :: Nil)))
+        }
         def unapplyImplicits(unapp: Tree): List[Tree] = {
           val res = List.newBuilder[Tree]
           def loop(unapp: Tree): Unit = unapp match {

tests/pos-macros/i19369/Macro_1.scala

@@ -0,0 +1,11 @@
+import scala.quoted._
+
+object Unapplier:
+  transparent inline def unapply(arg: Any): Option[Int] = ${unapplyImpl('arg)}
+
+  def unapplyImpl(using Quotes)(argExpr: Expr[Any]): Expr[Option[Int]] =
+    executionCount += 1
+    assert(executionCount == 1, "macro should only expand once")
+    '{Some(1)}
+
+  private var executionCount = 0

tests/pos-macros/i19369/Test_2.scala

@@ -0,0 +1,2 @@
+@main def main() =
+  val Unapplier(result) = Some(5)