Add POC of selector DSL

modules/parser-gen/src/main/scala/playground/parsergen/demo.scala

@@ -0,0 +1,52 @@
+case class Foo(bars: List[Bar]) {
+  def select[A](f: Foo.Selector => Selection[A]): List[A] = f(Foo.Selector(List(this))).path
+}
+
+object Foo {
+
+  case class Selector(path: List[Foo]) extends Selection[Foo] {
+    def bars: Bar.Selector = Bar.Selector(path.flatMap(_.bars))
+  }
+
+}
+
+case class Bar(baz: Option[Baz])
+
+object Bar {
+
+  case class Selector(path: List[Bar]) extends Selection[Bar] {
+    def baz: Baz.Selector = Baz.Selector(path.flatMap(_.baz))
+
+  }
+
+}
+
+case class Baz(names: List[Identifier])
+
+object Baz {
+
+  case class Selector(path: List[Baz]) extends Selection[Baz] {
+    def names: Identifier.Selector = Identifier.Selector(path.flatMap(_.names))
+  }
+
+}
+
+case class Identifier(value: String)
+
+object Identifier {
+
+  case class Selector(path: List[Identifier]) extends Selection[Identifier]
+}
+
+trait Selection[A] {
+  def path: List[A]
+}
+
+@main def demo = {
+  import util.chaining.*
+
+  Foo(List(Bar(Some(Baz(List("a", "b").map(Identifier.apply)))))).select(_.bars.baz).pipe(println)
+  Foo(List(Bar(Some(Baz(List("a", "b").map(Identifier.apply))))))
+    .select(_.bars.baz.names)
+    .pipe(println)
+}

modules/treesitter/src/main/scala/playground/treesitter4s/std/Selection.scala

@@ -0,0 +1,5 @@
+package playground.treesitter4s.std
+
+trait Selection[A] {
+  def path: List[A]
+}