Fix spliced-captured this

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -717,9 +717,12 @@ class TreePickler(pickler: TastyPickler, attributes: Attributes) {
             writeNat(idx)
             pickleType(tree.tpe, richTypes = true)
             args.foreach { arg =>
-              arg.tpe match
-                case _: TermRef if arg.isType => writeByte(EXPLICITtpt)
-                case _ =>
+              if arg.isType then
+                // Add EXPLICITtpt if the type can represent a type or a term.
+                // This is only needed if the tree of the type would be unpickled as a term tree.
+                arg.tpe match
+                  case _: TermRef | _: ThisType => writeByte(EXPLICITtpt)
+                  case _ =>
               pickleTree(arg)
             }
           }

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

@@ -203,6 +203,16 @@ class PickleQuotes extends MacroTransform {
   private def getPicklableHoleType(tpe: Type, isStagedClasses: Symbol => Boolean)(using Context) =
     new TypeOps.AvoidMap {
       def toAvoid(tp: NamedType) = !isStagedClasses(tp.typeSymbol) && !isStaticPrefix(tp)
+      override def apply(tp: Type): Type = tp match
+        case tp: ThisType if tp.typeSymbol.isLocal =>
+          // ThisType is only used inside a class.
+          // In general, either they don't appear in the type to be avoided, or
+          // it must be a class that encloses the block whose type is to be avoided.
+          // However, as we may be extracting a splice that contains a reference to
+          // a local class, we need to be careful to avoid the ThisType of the local
+          // class.
+          super.apply(tp.widen)
+        case _ => super.apply(tp)
     }.apply(tpe)
 }
 

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

@@ -167,14 +167,15 @@ class Splicing extends MacroTransform:
    *  ```
    */
   private class SpliceTransformer(spliceOwner: Symbol, isCaptured: Symbol => Boolean) extends Transformer:
-    private var refBindingMap = mutable.LinkedHashMap.empty[Symbol, (Tree, Symbol)]
+    private var refTermBindingMap = mutable.LinkedHashMap.empty[Symbol, (Tree, Symbol)]
+    private var refTypeBindingMap = mutable.LinkedHashMap.empty[Symbol, (Tree, Symbol)]
     /** Reference to the `Quotes` instance of the current level 1 splice */
     private var quotes: Tree | Null = null // TODO: add to the context
 
     def transformSplice(tree: tpd.Tree, tpe: Type, holeIdx: Int)(using Context): tpd.Tree =
       assert(level == 0)
       val newTree = transform(tree)
-      val (refs, bindings) = refBindingMap.values.toList.unzip
+      val (refs, bindings) = (refTypeBindingMap.values ++ refTermBindingMap.values).toList.unzip
       val bindingsTypes = bindings.map(_.termRef.widenTermRefExpr)
       val methType = MethodType(bindingsTypes, newTree.tpe)
       val meth = newSymbol(spliceOwner, nme.ANON_FUN, Synthetic | Method, methType)
@@ -212,6 +213,11 @@ class Splicing extends MacroTransform:
         case _: TypeTree | _: SingletonTypeTree =>
           if containsCapturedType(tree.tpe) && level >= 1 then getTagRefFor(tree)
           else tree
+        case _: This =>
+          if isCaptured(tree.symbol) then
+            val tag = getTagRefFor(tree)
+            spliced(tag.tpe)(capturedTerm(tree))
+          else super.transform(tree)
         case tree @ Assign(lhs: RefTree, rhs) =>
           if isCaptured(lhs.symbol) then transformSplicedAssign(tree)
           else super.transform(tree)
@@ -302,7 +308,7 @@ class Splicing extends MacroTransform:
         Param,
         defn.QuotedExprClass.typeRef.appliedTo(tpe),
       )
-      val bindingSym = refBindingMap.getOrElseUpdate(tree.symbol, (tree, newBinding))._2
+      val bindingSym = refTermBindingMap.getOrElseUpdate(tree.symbol, (tree, newBinding))._2
       ref(bindingSym)
 
     private def newQuotedTypeClassBinding(tpe: Type)(using Context) =
@@ -314,14 +320,14 @@ class Splicing extends MacroTransform:
       )
 
     private def capturedType(tree: Tree)(using Context): Symbol =
-      refBindingMap.getOrElseUpdate(tree.symbol, (TypeTree(tree.tpe), newQuotedTypeClassBinding(tree.tpe)))._2
+      refTypeBindingMap.getOrElseUpdate(tree.symbol, (TypeTree(tree.tpe), newQuotedTypeClassBinding(tree.tpe)))._2
 
     private def capturedPartTypes(quote: Quote)(using Context): Tree =
       val (tags, body1) = inContextWithQuoteTypeTags {
         val capturePartTypes = new TypeMap {
           def apply(tp: Type) = tp match {
             case typeRef: TypeRef if containsCapturedType(typeRef) =>
-              val termRef = refBindingMap
+              val termRef = refTypeBindingMap
                 .getOrElseUpdate(typeRef.symbol, (TypeTree(typeRef), newQuotedTypeClassBinding(typeRef)))._2.termRef
               val tagRef = getTagRef(termRef)
               tagRef

tests/pos-macros/this-type-capture/Macro_1.scala

@@ -0,0 +1,37 @@
+import scala.quoted.*
+
+object Macro:
+  inline def generateCode: Unit = ${ testThisPaths }
+
+  def testThisPaths(using Quotes): Expr[Unit] =
+    '{
+      trait E extends G:
+        type V
+        val f: F
+        ${ val expr = '{ println(this) }; expr }
+        ${ val expr = '{ println(f) }; expr }
+        ${ val expr = '{ println(this.f) }; expr }
+        ${ val expr = '{ println(??? : this.type) }; expr }
+        ${ val expr = '{ println(??? : V) }; expr }
+        ${ val expr = '{ println(??? : this.V) }; expr }
+        ${ val expr = '{ println(??? : this.f.V) }; expr }
+        ${ val expr = '{ println(??? : this.f.type) }; expr }
+        ${
+          val expr = '{
+            println(this)
+            println(f)
+            println(this.f)
+            println(??? : this.type)
+            println(??? : V)
+            println(??? : this.V)
+            println(??? : this.f.V)
+            println(??? : this.f.type)
+          }
+          expr
+        }
+      trait F:
+        type V
+    }
+
+trait G:
+  val f: Any

tests/pos-macros/this-type-capture/Test_2.scala

@@ -0,0 +1 @@
+@main def test = Macro.generateCode