Merge pull request #8523 from dotty-staging/add-prototye-conversion-with-dependent-functions-suport

Add prototype conversion with dependent functions support

Author: odersky

tests/pos/conversion-function-prototype.scala

@@ -0,0 +1,42 @@
+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
+
+}
+
+type ConversionFunction[+F <: Nothing => Any] =
+  ConversionFunction.ConversionFunction[F]
+
+object Test {
+
+  {
+    given ConversionFunction[Int => String] = ConversionFunction(_.toString)
+    // val a: String = 3
+    val a: String = ConversionFunction.get[3 => String].apply(3)
+  }
+
+  trait X {
+    type T
+    def t: T
+  }
+  val x: X = ???
+
+  {
+    given ConversionFunction[(x: X) => x.T] = ConversionFunction((x: X) => x.t)
+    // val a: x.T = x
+    val a: x.T = ConversionFunction.get[(x: X) => x.T].apply(x)
+  }
+
+  {
+    given ConversionFunction[(x: X) => x.T] = ConversionFunction(_.t)
+    // val a: x.T = x
+    val a: x.T = ConversionFunction.get[(x: X) => x.T].apply(x)
+  }
+
+}