Add prototype conversion with dependent functions support

Author: nicolasstucki

tests/pos/conversion-function-prototype.scala

@@ -0,0 +1,67 @@
+package scala
+
+
+object ConversionFunction {
+
+  opaque type ConversionFunction[+F <: Nothing => Any] = F
+
+  def apply[F <: Nothing => Any](f: F): ConversionFunction[F] = f
+  def get[F <: Nothing => Any](using f: ConversionFunction[F]): F = f
+
+}
+
+given [F <: Nothing => Any] as Conversion/*Function*/[F, ConversionFunction[F]] = (x: F) => ConversionFunction.apply(x)
+
+type ConversionFunction[+F <: Nothing => Any] =
+  ConversionFunction.ConversionFunction[F]
+
+type Conversion2[T, U] =
+  ConversionFunction.ConversionFunction[T => U]
+
+object Test {
+
+  {
+    given Conversion2[Int, String] = (x: Int) => x.toString
+    // val a: String = 3
+    val a: String = ConversionFunction.get[3 => String].apply(3)
+  }
+
+  {
+    given ConversionFunction[Int => String] = (x: Int) => x.toString
+    // val a: String = 3
+    val a: String = ConversionFunction.get[3 => String].apply(3)
+  }
+
+  {
+    given ConversionFunction[(x: Int) => x.type] = ConversionFunction((x: Int) => x)
+    // val a: String = 3
+    val a: Int = ConversionFunction.get[3 => Int].apply(3)
+  }
+
+
+  {
+    trait X {
+      type T
+      def t: T
+    }
+    val x: X = ???
+
+    given ConversionFunction[(x: X) => x.T] = (x: X) => x.t
+    // val a: String = 3
+    val a: x.T = ConversionFunction.get[(x: X) => x.T].apply(x)
+  }
+
+
+  {
+    trait X {
+      type T
+      def t: T
+    }
+    val x: X = ???
+
+    given ConversionFunction[(x: X) => x.T] = ConversionFunction(_.t)
+    // val a: String = 3
+    val a: x.T = ConversionFunction.get[(x: X) => x.T].apply(x)
+  }
+
+}