Add reflect TypeRepr.dealiasKeepOpaques (#18583)

From #18562

Author: smarter

compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala

@@ -1790,6 +1790,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
         def widenTermRefByName: TypeRepr = self.widenTermRefExpr
         def widenByName: TypeRepr = self.widenExpr
         def dealias: TypeRepr = self.dealias
+        def dealiasKeepOpaques: TypeRepr = self.dealiasKeepOpaques
         def simplified: TypeRepr = self.simplified
         def classSymbol: Option[Symbol] =
           if self.classSymbol.exists then Some(self.classSymbol.asClass)

library/src/scala/quoted/Quotes.scala

@@ -2652,6 +2652,9 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
         /** Follow aliases, annotated types until type is no longer alias type, annotated type. */
         def dealias: TypeRepr
 
+        /** Follow non-opaque aliases, annotated types until type is no longer alias type, annotated type. */
+        def dealiasKeepOpaques: TypeRepr
+
         /** A simplified version of this type which is equivalent wrt =:= to this type.
         *  Reduces typerefs, applied match types, and and or types.
         */

project/MiMaFilters.scala

@@ -9,6 +9,7 @@ object MiMaFilters {
     ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule.ValOrDefDefMethods"),
     ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#defnModule.FunctionClass"),
     ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#defnModule.PolyFunctionClass"),
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#TypeReprMethods.dealiasKeepOpaques"),
   )
   val TastyCore: Seq[ProblemFilter] = Seq(
     ProblemFilters.exclude[DirectMissingMethodProblem]("dotty.tools.tasty.TastyFormat.EXPLICITtpt"),

tests/run-macros/tasty-dealiasKeepOpaques.check

@@ -0,0 +1,10 @@
+java.lang.String
+java.lang.String
+scala.collection.immutable.List[Test_2$package.A]
+scala.collection.immutable.List[scala.Int]
+Test_2$package.OA
+Test_2$package.OB
+Test_2$package.OC[scala.Int]
+Test_2$package.OA
+Test_2$package.OB
+Test_2$package.OC[scala.Int]

tests/run-macros/tasty-dealiasKeepOpaques/Macro_1.scala

@@ -0,0 +1,8 @@
+import scala.quoted.*
+
+inline def dealiasKeepOpaques[T]: String = ${ impl[T] }
+
+def impl[T: Type](using Quotes) : Expr[String] = {
+  import quotes.reflect.*
+  Expr(TypeRepr.of[T].dealiasKeepOpaques.show)
+}

tests/run-macros/tasty-dealiasKeepOpaques/Test_2.scala

@@ -0,0 +1,29 @@
+type A = String
+type B = List[A]
+type C[X] = List[X]
+
+opaque type OA = String
+object OA:
+  def test = println(dealiasKeepOpaques[OA])
+
+opaque type OB = List[A]
+object OB:
+  def test = println(dealiasKeepOpaques[OB])
+
+opaque type OC[X] = List[X]
+object OC:
+  def test = println(dealiasKeepOpaques[OC[Int]])
+
+
+@main def Test: Unit = {
+  println(dealiasKeepOpaques[String])
+  println(dealiasKeepOpaques[A])
+  println(dealiasKeepOpaques[B])
+  println(dealiasKeepOpaques[C[Int]])
+  println(dealiasKeepOpaques[OA])
+  println(dealiasKeepOpaques[OB])
+  println(dealiasKeepOpaques[OC[Int]])
+  OA.test
+  OB.test
+  OC.test
+}