[chore]: Add regression tests for #23237 (#23405)

Adds regression tests for #23237 to prevent reintroducing regression
from #21744

Author: WojciechMazur

tests/pos/i23237a.scala

@@ -0,0 +1,29 @@
+sealed trait Dim
+trait _2D extends Dim
+trait _3D extends Dim
+
+sealed abstract class IntVector[D]
+object IntVector{
+  def apply[D](d: Array[Int]): IntVector[D] = ???
+  def apply(x: Int, y: Int): IntVector2D = IntVector2D(x, y)
+  def apply(x: Int, y: Int, z: Int): IntVector3D = IntVector3D(x, y, z)
+}
+case class IntVector2D(i: Int, j: Int) extends IntVector[_2D]
+case class IntVector3D(i: Int, j: Int, k: Int) extends IntVector[_3D]
+
+type DiscreteImage[D, A] = DiscreteField[D, DiscreteImageDomain, A]
+class DiscreteField[D, DDomain[D] <: DiscreteDomain[D], A](val domain: DDomain[D], val data: IndexedSeq[A])  extends PartialFunction[PointId, A] {
+  override def apply(v1: PointId) = ???
+  override def isDefinedAt(ptId: PointId) = ???
+}
+object DiscreteField{
+    implicit class DiscreteImageOps[D, A](discreteField: DiscreteField[D, DiscreteImageDomain, A]) {
+      def apply(idx: IntVector[D]): A = ???
+      def isDefinedAt(idx: IntVector[D]): Boolean = ???
+  }
+}
+trait DiscreteDomain[D]
+trait DiscreteImageDomain[D] extends DiscreteDomain[D]
+final case class PointId(id: Int) extends AnyVal
+
+def test[S](img: DiscreteImage[_3D, S]) = img(IntVector(1, 2, 3))

tests/pos/i23237b.scala

@@ -0,0 +1,23 @@
+object types{
+  final case class vec2(x: Float, y: Float)
+  final case class vec4(x: Float, y: Float, z: Float, w: Float)
+  object vec4:
+    def apply(xy: vec2, z: Float, w: Float): vec4 = vec4(xy.x, xy.y, z, w)
+
+  opaque type Shader[In, Out] = In => Out
+  object Shader:
+    inline def apply[In, Out](f: In => Out): Shader[In, Out] = f
+    inline def apply[In](f: In => Unit): Shader[In, Unit]    = f
+    inline def apply(body: => Any): Shader[Unit, Unit] = (_: Unit) => body
+}
+import types.*
+
+class GLSLEnvTests {
+  case class FragEnv(UV: vec2)
+
+  inline def fragment: Shader[FragEnv, vec4] =
+    Shader { env =>
+      val x = env.UV
+      vec4(env.UV, 0.0f, 1.0f)
+    }
+}