Fix mapping and pickling of non-trivial annotated types

`Annotation.mapWith` maps an `Annotation` with a type map `tm`. Before actually applying `tm` to the annotation’s `tree`, it first checks if `tm` would result in any change by traversing the annotation’s arguments, and checking if the mapped type of any any tree is different. This optimization had two problems: it didn’t include type parameters, and used `frozen_=:=`  to compare types, which failed to detected some changes. This commit changes `Annotation.arguments` to also include type parameters, and changes `Annotation.MapWith` to use `==` to compare types instead of `frozen_=:=`.

Furthermore, in case of changes, the symbol in the annotation's tree should be copied to make sure that the same symbol is not used for different trees. This commit achieves this by using a custom `TreeTypeMap` with an overridden `withMappedSyms` method where `Symbols.mapSymbols` is called with the argument `mapAlways = true`.

Finally, positions of trees that appear only inside `AnnotatedType` were not pickled. This commit also fixes this.

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -134,10 +134,10 @@ trait TreeInfo[T <: Untyped] { self: Trees.Instance[T] =>
       case _ => argss
     loop(tree, Nil)
 
-  /** All term arguments of an application in a single flattened list */
+  /** All type and term arguments of an application in a single flattened list */
   def allArguments(tree: Tree): List[Tree] = unsplice(tree) match {
     case Apply(fn, args) => allArguments(fn) ::: args
-    case TypeApply(fn, _) => allArguments(fn)
+    case TypeApply(fn, args) => allArguments(fn) ::: args
     case Block(_, expr) => allArguments(expr)
     case _ => Nil
   }

compiler/src/dotty/tools/dotc/core/Annotations.scala

@@ -3,8 +3,9 @@ package dotc
 package core
 
 import Symbols.*, Types.*, Contexts.*, Constants.*, Phases.*
-import ast.tpd, tpd.*
-import util.Spans.Span
+import ast.{tpd, untpd, TreeTypeMap}
+import tpd.*
+import util.Spans.{Span, NoSpan}
 import printing.{Showable, Printer}
 import printing.Texts.Text
 
@@ -30,7 +31,7 @@ object Annotations {
     def derivedAnnotation(tree: Tree)(using Context): Annotation =
       if (tree eq this.tree) this else Annotation(tree)
 
-    /** All arguments to this annotation in a single flat list */
+    /** All type and term arguments to this annotation in a single flat list */
     def arguments(using Context): List[Tree] = tpd.allArguments(tree)
 
     def argument(i: Int)(using Context): Option[Tree] = {
@@ -57,15 +58,25 @@ object Annotations {
       val args = arguments
       if args.isEmpty then this
       else
+        // Checks if `tm` would result in any change by applying it to types
+        // inside the annotations' arguments and checking if the resulting types
+        // are different.
         val findDiff = new TreeAccumulator[Type]:
           def apply(x: Type, tree: Tree)(using Context): Type =
             if tm.isRange(x) then x
             else
               val tp1 = tm(tree.tpe)
-              foldOver(if tp1 frozen_=:= tree.tpe then x else tp1, tree)
+              foldOver(if tp1 == tree.tpe then x else tp1, tree)
         val diff = findDiff(NoType, args)
         if tm.isRange(diff) then EmptyAnnotation
-        else if diff.exists then derivedAnnotation(tm.mapOver(tree))
+        else if diff.exists then
+          // In case of changes, the symbol in the annotation's tree should be
+          // copied so that the same symbol is not used for different trees.
+          val ttm =
+            new TreeTypeMap(typeMap = tm):
+              final override def withMappedSyms(syms: List[Symbol]): TreeTypeMap =
+                withMappedSyms(syms, mapSymbols(syms, this, mapAlways = true))
+          derivedAnnotation(ttm.transform(tree))
         else this
 
     /** Does this annotation refer to a parameter of `tl`? */

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

@@ -33,6 +33,7 @@ object PositionPickler:
       pickler: TastyPickler,
       addrOfTree: TreeToAddr,
       treeAnnots: untpd.MemberDef => List[tpd.Tree],
+      typeAnnots: List[tpd.Tree],
       relativePathReference: String,
       source: SourceFile,
       roots: List[Tree],
@@ -136,6 +137,9 @@ object PositionPickler:
     }
     for (root <- roots)
       traverse(root, NoSource)
+
+    for annotTree <- typeAnnots do
+      traverse(annotTree, NoSource)
   end picklePositions
 end PositionPickler
 

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

@@ -40,6 +40,10 @@ class TreePickler(pickler: TastyPickler, attributes: Attributes) {
    */
   private val annotTrees = util.EqHashMap[untpd.MemberDef, mutable.ListBuffer[Tree]]()
 
+  /** A set of annotation trees appearing in annotated types.
+   */
+  private val annotatedTypeTrees = mutable.ListBuffer[Tree]()
+
   /** A map from member definitions to their doc comments, so that later
    *  parallel comment pickling does not need to access symbols of trees (which
    *  would involve accessing symbols of named types and possibly changing phases
@@ -56,6 +60,8 @@ class TreePickler(pickler: TastyPickler, attributes: Attributes) {
     val ts = annotTrees.lookup(tree)
     if ts == null then Nil else ts.toList
 
+  def typeAnnots: List[Tree] = annotatedTypeTrees.toList
+
   def docString(tree: untpd.MemberDef): Option[Comment] =
     Option(docStrings.lookup(tree))
 
@@ -266,6 +272,7 @@ class TreePickler(pickler: TastyPickler, attributes: Attributes) {
     case tpe: AnnotatedType =>
       writeByte(ANNOTATEDtype)
       withLength { pickleType(tpe.parent, richTypes); pickleTree(tpe.annot.tree) }
+      annotatedTypeTrees += tpe.annot.tree
     case tpe: AndType =>
       writeByte(ANDtype)
       withLength { pickleType(tpe.tp1, richTypes); pickleType(tpe.tp2, richTypes) }

compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala

@@ -224,7 +224,7 @@ object PickledQuotes {
     if tree.span.exists then
       val positionWarnings = new mutable.ListBuffer[Message]()
       val reference = ctx.settings.sourceroot.value
-      PositionPickler.picklePositions(pickler, treePkl.buf.addrOfTree, treePkl.treeAnnots, reference,
+      PositionPickler.picklePositions(pickler, treePkl.buf.addrOfTree, treePkl.treeAnnots, treePkl.typeAnnots, reference,
         ctx.compilationUnit.source, tree :: Nil, positionWarnings)
       positionWarnings.foreach(report.warning(_))
 

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

@@ -143,7 +143,7 @@ class Pickler extends Phase {
           if tree.span.exists then
             val reference = ctx.settings.sourceroot.value
             PositionPickler.picklePositions(
-                pickler, treePkl.buf.addrOfTree, treePkl.treeAnnots, reference,
+                pickler, treePkl.buf.addrOfTree, treePkl.treeAnnots, treePkl.typeAnnots, reference,
                 unit.source, tree :: Nil, positionWarnings,
                 scratch.positionBuffer, scratch.pickledIndices)
 

tests/pos/annot-17939.scala

@@ -0,0 +1,7 @@
+class qualified[T](f: T => Boolean) extends annotation.StaticAnnotation
+
+class Box[T](val x: T)
+class Box2(val x: Int)
+
+class A(a: String @qualified((x: Int) => Box(3).x == 3)) // crash
+class A2(a2: String @qualified((x: Int) => Box2(3).x == 3)) // works

tests/pos/annot-17939b.scala

@@ -0,0 +1,10 @@
+import scala.annotation.Annotation
+class myRefined(f: ? => Boolean) extends Annotation
+
+def test(axes: Int) = true
+
+trait Tensor:
+  def mean(axes: Int): Int @myRefined(_ => test(axes))
+
+class TensorImpl() extends Tensor:
+  def mean(axes: Int) = ???

tests/pos/annot-18064.scala

@@ -0,0 +1,9 @@
+//> using options "-Xprint:typer"
+
+class myAnnot[T]() extends annotation.Annotation
+
+trait Tensor[T]:
+  def add: Tensor[T] @myAnnot[T]()
+
+class TensorImpl[A]() extends Tensor[A]:
+  def add /* : Tensor[A] @myAnnot[A] */ = this

tests/pos/annot-19846.scala

@@ -0,0 +1,8 @@
+class qualified[T](predicate: T => Boolean) extends annotation.StaticAnnotation
+
+class EqualPair(val x: Int, val y: Int @qualified[Int](it => it == x))
+
+@main def main =
+  val p = EqualPair(42, 42)
+  val y = p.y
+  println(42)

tests/pos/annot-19846b.scala

@@ -0,0 +1,7 @@
+class lambdaAnnot(g: () => Int) extends annotation.StaticAnnotation
+
+def f(x: Int): Int @lambdaAnnot(() => x) = x
+
+object Test:
+  val y: Int = ???
+  val z /* : Int @lambdaAnnot(() => y) */ = f(y)

tests/pos/annot-5789.scala

@@ -0,0 +1,10 @@
+class Annot[T] extends scala.annotation.Annotation
+
+class D[T](val f: Int@Annot[T])
+
+object A{
+  def main(a:Array[String]) = {
+    val c = new D[Int](1)
+    c.f
+  }
+}

tests/printing/annot-18064.check

@@ -0,0 +1,16 @@
+[[syntax trees at end of                     typer]] // tests/printing/annot-18064.scala
+package <empty> {
+  class myAnnot[T >: Nothing <: Any]() extends annotation.Annotation() {
+    T
+  }
+  trait Tensor[T >: Nothing <: Any]() extends Object {
+    T
+    def add: Tensor[Tensor.this.T] @myAnnot[T]
+  }
+  class TensorImpl[A >: Nothing <: Any]() extends Object(), Tensor[
+    TensorImpl.this.A] {
+    A
+    def add: Tensor[A] @myAnnot[A] = this
+  }
+}
+

tests/printing/annot-18064.scala

@@ -0,0 +1,9 @@
+//> using options "-Xprint:typer"
+
+class myAnnot[T]() extends annotation.Annotation
+
+trait Tensor[T]:
+  def add: Tensor[T] @myAnnot[T]()
+
+class TensorImpl[A]() extends Tensor[A]:
+  def add /* : Tensor[A] @myAnnot[A] */ = this

tests/printing/annot-19846b.check

@@ -0,0 +1,33 @@
+[[syntax trees at end of                     typer]] // tests/printing/annot-19846b.scala
+package <empty> {
+  class lambdaAnnot(g: () => Int) extends scala.annotation.Annotation(),
+    annotation.StaticAnnotation {
+    private[this] val g: () => Int
+  }
+  final lazy module val Test: Test = new Test()
+  final module class Test() extends Object() { this: Test.type =>
+    val y: Int = ???
+    val z:
+      Int @lambdaAnnot(
+        {
+          def $anonfun(): Int = Test.y
+          closure($anonfun)
+        }
+      )
+     = f(Test.y)
+  }
+  final lazy module val annot-19846b$package: annot-19846b$package =
+    new annot-19846b$package()
+  final module class annot-19846b$package() extends Object() {
+    this: annot-19846b$package.type =>
+    def f(x: Int):
+      Int @lambdaAnnot(
+        {
+          def $anonfun(): Int = x
+          closure($anonfun)
+        }
+      )
+     = x
+  }
+}
+

tests/printing/annot-19846b.scala

@@ -0,0 +1,7 @@
+class lambdaAnnot(g: () => Int) extends annotation.StaticAnnotation
+
+def f(x: Int): Int @lambdaAnnot(() => x) = x
+
+object Test:
+  val y: Int = ???
+  val z /* : Int @lambdaAnnot(() => y) */ = f(y)