Merge pull request #6112 from dotty-staging/add-tasty-type-dealias

Add TASYTy Reflect type dealias

Author: nicolasstucki

compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala

@@ -994,6 +994,8 @@ class KernelImpl(val rootContext: core.Contexts.Context, val rootPosition: util.
     */
   def Type_widen(self: Type)(implicit ctx: Context): Type = self.widen
 
+  def Type_dealias(self: Type)(implicit ctx: Context): Type = self.dealias
+
   def Type_classSymbol(self: Type)(implicit ctx: Context): Option[ClassSymbol] =
     if (self.classSymbol.exists) Some(self.classSymbol.asClass) else None
 

library/src/scala/tasty/reflect/Kernel.scala

@@ -796,6 +796,12 @@ trait Kernel {
     */
   def Type_widen(self: Type)(implicit ctx: Context): Type
 
+  /** Follow aliases and dereferences LazyRefs, annotated types and instantiated
+   *  TypeVars until type is no longer alias type, annotated type, LazyRef,
+   *  or instantiated type variable.
+   */
+  def Type_dealias(self: Type)(implicit ctx: Context): Type
+
   def Type_classSymbol(self: Type)(implicit ctx: Context): Option[ClassSymbol]
 
   def Type_typeSymbol(self: Type)(implicit ctx: Context): Symbol

library/src/scala/tasty/reflect/TypeOrBoundsOps.scala

@@ -11,6 +11,13 @@ trait TypeOrBoundsOps extends Core {
     def =:=(that: Type)(implicit ctx: Context): Boolean = kernel.`Type_=:=`(self)(that)
     def <:<(that: Type)(implicit ctx: Context): Boolean = kernel.`Type_<:<`(self)(that)
     def widen(implicit ctx: Context): Type = kernel.Type_widen(self)
+
+    /** Follow aliases and dereferences LazyRefs, annotated types and instantiated
+     *  TypeVars until type is no longer alias type, annotated type, LazyRef,
+     *  or instantiated type variable.
+     */
+    def dealias(implicit ctx: Context): Type = kernel.Type_dealias(self)
+
     def classSymbol(implicit ctx: Context): Option[ClassSymbol] = kernel.Type_classSymbol(self)
     def typeSymbol(implicit ctx: Context): Symbol = kernel.Type_typeSymbol(self)
     def isSingleton(implicit ctx: Context): Boolean = kernel.Type_isSingleton(self)

tests/run/tasty-dealias.check

@@ -0,0 +1,4 @@
+lang.String
+lang.String
+immutable.List[A]
+immutable.List[scala.Int]

tests/run/tasty-dealias/quoted_1.scala

@@ -0,0 +1,12 @@
+import scala.quoted._
+import scala.tasty._
+
+object Macros {
+
+  inline def dealias[T]: String = ${ impl('[T]) }
+
+  def impl[T](x: quoted.Type[T])(implicit reflect: Reflection): Expr[String] = {
+    import reflect._
+    x.unseal.tpe.dealias.showCode.toExpr
+  }
+}

tests/run/tasty-dealias/quoted_2.scala

@@ -0,0 +1,15 @@
+
+import Macros.dealias
+
+object Test {
+
+  def main(args: Array[String]): Unit = {
+    type A = String
+    type B = List[A]
+    type C[X] = List[X]
+    println(dealias[String])
+    println(dealias[A])
+    println(dealias[B])
+    println(dealias[C[Int]])
+  }
+}