Dealias type references when healing types in quotes (#17049)

We where only doing the dealiasing if the type had no prefix but missed
it if the type reference was on some path.

Fixes #17037

Author: nicolasstucki

compiler/src/dotty/tools/dotc/transform/PCPCheckAndHeal.scala

@@ -192,11 +192,9 @@ class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(
         case tp: TypeRef =>
           tp.prefix match
             case NoPrefix if level > levelOf(tp.symbol) && !tp.typeSymbol.hasAnnotation(defn.QuotedRuntime_SplicedTypeAnnot) =>
-              val tp1 = tp.dealias
-              if tp1 != tp then apply(tp1)
-              else tryHeal(tp.symbol, tp, pos)
+              tryHealTypeOfType(tp.symbol, tp, pos)
             case prefix: ThisType if !tp.symbol.isStatic && level > levelOf(prefix.cls) =>
-              tryHeal(tp.symbol, tp, pos)
+              tryHealTypeOfType(tp.symbol, tp, pos)
             case prefix: TermRef if tp.symbol.isTypeSplice =>
               prefix.symbol.info.argInfos match
                 case (tb: TypeBounds) :: _ =>
@@ -205,7 +203,7 @@ class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(
               // Heal explicit type splice in the code
               if level > 0 then getQuoteTypeTags.getTagRef(prefix) else tp
             case prefix: TermRef if !prefix.symbol.isStatic && level > levelOf(prefix.symbol) =>
-              tryHeal(prefix.symbol, tp, pos)
+              tryHealTypeOfType(prefix.symbol, tp, pos)
             case _ =>
               mapOver(tp)
         case tp @ TermRef(NoPrefix, _) if !tp.symbol.isStatic && level > levelOf(tp.symbol) =>
@@ -217,6 +215,17 @@ class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(
           derivedAnnotatedType(tp, apply(tp.parent), tp.annot.derivedAnnotation(newAnnotTree))
         case _ =>
           mapOver(tp)
+
+    /** Try to dealias or heal reference to type `T` used in a higher level than its definition.
+     *  Returns a reference to a type tag generated by `QuoteTypeTags` that contains a
+     *  reference to a type alias containing the equivalent of `${summon[quoted.Type[T]]}`.
+     *  Emits and error if `T` cannot be healed and returns `T`.
+     */
+    private def tryHealTypeOfType(sym: Symbol, tp: TypeRef, pos: SrcPos)(using Context): Type = {
+      val tp1 = tp.dealias
+      if tp1 != tp then apply(tp1)
+      else tryHeal(tp.symbol, tp, pos)
+    }
   }
 
   /** Check phase consistency of terms and heal inconsistent type references. */

tests/pos-macros/i17037.scala

@@ -0,0 +1,8 @@
+import scala.quoted.*
+
+class Foo:
+  type Bar = Int
+
+def macroImpl(using Quotes) =
+  val foo = new Foo
+  Type.of[foo.Bar]

tests/pos-macros/i17037b.scala

@@ -0,0 +1,10 @@
+import scala.quoted.*
+
+class Foo:
+  type Bar = Int
+
+def macroImpl(using Quotes) =
+  val foo = Foo()
+  Type.of[foo.Bar] match
+    case '[foo.Bar] => '{true}
+    case _ => '{false}

tests/pos-macros/i17037c.scala

@@ -0,0 +1,7 @@
+import scala.quoted.*
+
+class Foo:
+  type Bar = Int
+  def macroImpl(using Quotes) =
+    val foo = new Foo
+    Type.of[this.Bar]