Fix: SubtypeCustom[A] should behave like subtype of A (#1328)

* Add test validating that passing a `Subtype[String]` and a `SubtypeCustom[String]` to a function asking for a `String` does compile

* clean

* Fix: `SubtypeCustom[A]` should behave like subtype of `A`

* Add missing `override`

core-tests/shared/src/test/scala-3/zio/prelude/NewtypeSpecTypes.scala

@@ -88,10 +88,10 @@ object NewtypeSpecTypes {
   Pin(1000, 1001, 9998, 9999)
 
   object Palindrome extends NewtypeCustom[String] {
-    protected def validate(value: String) =
+    override protected def validate(value: String) =
       PalindromeValidator.validate(value)
 
-    protected inline def validateInline(inline value: String) =
+    override protected inline def validateInline(inline value: String) =
       ${ PalindromeValidator.validateInlineImpl('value) }
   }
 
@@ -106,6 +106,15 @@ object NewtypeSpecTypes {
     def unsafeWrap(s: String): Type = wrap(s)
   }
 
+  type NonEmptyString = NonEmptyString.Type
+  object NonEmptyString extends SubtypeCustom[String] {
+    override protected def validate(value: String) =
+      NonEmptyStringValidator.validate(value)
+
+    override protected inline def validateInline(inline value: String) =
+      ${ NonEmptyStringValidator.validateInlineImpl('value) }
+  }
+
   // These should compile
   GithubHeaderKey("X-Github-Request-Id")
   GithubHeaderKey("X-GitHub-Request-Id")
@@ -125,4 +134,9 @@ object NewtypeSpecTypes {
   GmailEmail("[email protected]")
   GmailEmail("[email protected]")
   GmailEmail("[email protected]")
+
+  def takeString(s: String): Unit = ()
+  // These should compile
+  takeString(GithubHeaderKey("X-Github-Request-Id"))
+  takeString(NonEmptyString("Hello"))
 }

core-tests/shared/src/test/scala-3/zio/prelude/validators.scala

@@ -6,3 +6,9 @@ object PalindromeValidator
     extends Validator[String](str =>
       if (str.reverse == str) Right(()) else Left(AssertionError.Failure("isPalindrome"))
     )
+
+object NonEmptyStringValidator
+    extends Validator[String]((s: String) =>
+      if (s.isBlank) Left(AssertionError.failure("NonEmptyString cannot be empty"))
+      else Right(())
+    )

core/shared/src/main/scala-3/zio/prelude/Newtype.scala

@@ -127,7 +127,7 @@ abstract class NewtypeCustom[A] {
 }
 
 abstract class SubtypeCustom[A] extends NewtypeCustom[A] {
-  type Base <: A
+  override type Type <: A
 }
 
 abstract class Newtype[A] extends NewtypeCustom[A] {