Merge pull request #8957 from dotty-staging/fix-#8879

Fix #8879: Add Reflection.Type.select

Author: nicolasstucki

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

@@ -1215,6 +1215,9 @@ class ReflectionCompilerInterface(val rootContext: core.Contexts.Context) extend
     tpNoRefinement != self && defn.isNonRefinedFunction(tpNoRefinement)
   }
 
+  def Type_select(self: Type)(sym: Symbol)(using ctx: Context): Type =
+    self.select(sym)
+
   type ConstantType = Types.ConstantType
 
   def isInstanceOfConstantType(using ctx: Context): IsInstanceOf[ConstantType] = new {

library/src/scala/tasty/Reflection.scala

@@ -1678,6 +1678,9 @@ class Reflection(private[scala] val internal: CompilerInterface) { self =>
      *  @see `isFunctionType`
      */
     def isDependentFunctionType(using ctx: Context): Boolean = internal.Type_isDependentFunctionType(self)
+
+    /** The type <this . sym>, reduced if possible */
+    def select(sym: Symbol)(using ctx: Context): Type = internal.Type_select(self)(sym)
   }
 
   given (using ctx: Context) as IsInstanceOf[Type] = internal.isInstanceOfType

library/src/scala/tasty/reflect/CompilerInterface.scala

@@ -885,7 +885,6 @@ trait CompilerInterface {
    */
   def Type_isFunctionType(self: Type)(using ctx: Context): Boolean
 
-
   /** Is this type an context function type?
    *
    *  @see `Type_isFunctionType`
@@ -904,6 +903,9 @@ trait CompilerInterface {
    */
   def Type_isDependentFunctionType(self: Type)(using ctx: Context): Boolean
 
+  /** The type <this . sym>, reduced if possible */
+  def Type_select(self: Type)(sym: Symbol)(using ctx: Context): Type
+
   /** A singleton type representing a known constant value */
   type ConstantType <: Type
 

tests/pos-macros/i8879/Macro_1.scala

@@ -0,0 +1,23 @@
+case class Foo[A](a: A)
+
+object Test {
+
+  import scala.quoted._
+
+  def impl[T](t: T)(using qctx: QuoteContext, tt: Type[T]): Expr[Any] = {
+
+    import qctx.tasty._
+    import util._
+
+    val foo = typeOf[Foo[String]]
+    val symbol = foo.typeSymbol.field("a")
+    val a = foo.select(symbol)
+    assert(a <:< defn.StringType)
+
+    '{???}
+  }
+
+
+  inline def apply[T](inline t: T) = ${ Test.impl('t )}
+
+}

tests/pos-macros/i8879/Test_2.scala

@@ -0,0 +1,6 @@
+
+object Run {
+  def test(): Unit = {
+    Test[Foo[String]](Foo("moo"))
+  }
+}