Lift arguments of explicitly constructed annotations (#22553)

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

@@ -166,6 +166,36 @@ object Mode {
    */
   val ForceInline: Mode = newMode(29, "ForceInline")
 
+  /** Are we typing the argument of an annotation?
+   *
+   *  This mode is used through [[Applications.isAnnotConstr]] to avoid lifting
+   *  arguments of annotation constructors. This mode is disabled in nested
+   *  applications (from [[ProtoTypes.typedArg]]) and in "explicit" annotation
+   *  constructors applications (annotation classes constructed with `new`).
+   *
+   *  In the following example:
+   *
+   *  ```scala
+   *  @annot(y = new annot(y = Array("World"), x = 1), x = 2)
+   *  ```
+   *
+   *  the mode will be set when typing `@annot(...)` but not when typing
+   *  `new annot(...)`, such that the arguments of the former are not lifted but
+   *  the arguments of the later can be:
+   *
+   *  ```scala
+   *  @annot(x = 2, y = {
+   *    val y$3: Array[String] =
+   *      Array.apply[String](["World" : String]*)(
+   *        scala.reflect.ClassTag.apply[String](classOf[String]))
+   *    new annot(x = 1, y = y$3)
+   *  })
+   *  ```
+   *
+   *  See #22035, #22526, #22553 and `dependent-annot-default-args.scala`.
+   */
+  val InAnnotation: Mode = newMode(30, "InAnnotation")
+
   /** Skip inlining of methods. */
   val NoInline: Mode = newMode(31, "NoInline")
 }

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -694,9 +694,11 @@ trait Applications extends Compatibility {
       sym.is(JavaDefined) && sym.isConstructor && sym.owner.is(JavaAnnotation)
 
 
-    /** Is `sym` a constructor of an annotation? */
-    def isAnnotConstr(sym: Symbol): Boolean =
-      sym.isConstructor && sym.owner.isAnnotation
+    /** Is `sym` a constructor of an annotation class, and are we in an
+     *  annotation? If so, we don't lift arguments. See [[Mode.InAnnotation]].
+     */
+    protected final def isAnnotConstr(sym: Symbol): Boolean =
+      ctx.mode.is(Mode.InAnnotation) && sym.isConstructor && sym.owner.isAnnotation
 
     /** Match re-ordered arguments against formal parameters
      *  @param n   The position of the first parameter in formals in `methType`.
@@ -994,9 +996,7 @@ trait Applications extends Compatibility {
                 case (arg: NamedArg, _) => arg
                 case (arg, name)        => NamedArg(name, arg)
               }
-          else if isAnnotConstr(methRef.symbol) then
-            typedArgs
-          else if !sameSeq(args, orderedArgs) && !typedArgs.forall(isSafeArg) then
+          else if !isAnnotConstr(methRef.symbol) && !sameSeq(args, orderedArgs) && !typedArgs.forall(isSafeArg) then
             // need to lift arguments to maintain evaluation order in the
             // presence of argument reorderings.
             // (never do this for Java annotation constructors, hence the 'else if')

compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala

@@ -536,8 +536,8 @@ object ProtoTypes {
     def typedArg(arg: untpd.Tree, formal: Type)(using Context): Tree = {
       val wideFormal = formal.widenExpr
       val argCtx =
-        if wideFormal eq formal then ctx
-        else ctx.withNotNullInfos(ctx.notNullInfos.retractMutables)
+        if wideFormal eq formal then ctx.retractMode(Mode.InAnnotation)
+        else ctx.retractMode(Mode.InAnnotation).withNotNullInfos(ctx.notNullInfos.retractMutables)
       val locked = ctx.typerState.ownedVars
       val targ = cacheTypedArg(arg,
         typer.typedUnadapted(_, wideFormal, locked)(using argCtx),

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2779,7 +2779,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
     def isInner(owner: Symbol) = owner == sym || sym.is(Param) && owner == sym.owner
     val outer = ctx.outersIterator.dropWhile(c => isInner(c.owner)).next()
     def local: FreshContext = outer.fresh.setOwner(newLocalDummy(sym.owner))
-    sym.owner.infoOrCompleter match
+    val ctx0 = sym.owner.infoOrCompleter match
       case completer: Namer#Completer
       if sym.is(Param) && completer.completerTypeParams(sym).nonEmpty =>
         // Create a new local context with a dummy owner and a scope containing the
@@ -2788,6 +2788,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         local.setScope(newScopeWith(completer.completerTypeParams(sym)*))
       case _ =>
         if outer.owner.isClass then local else outer
+    ctx0.addMode(Mode.InAnnotation)
 
   def completeAnnotations(mdef: untpd.MemberDef, sym: Symbol)(using Context): Unit = {
     // necessary to force annotation trees to be computed.
@@ -2802,7 +2803,8 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   }
 
   def typedAnnotation(annot: untpd.Tree)(using Context): Tree =
-    checkAnnotClass(checkAnnotArgs(typed(annot)))
+    val typedAnnot = withMode(Mode.InAnnotation)(typed(annot))
+    checkAnnotClass(checkAnnotArgs(typedAnnot))
 
   def registerNowarn(tree: Tree, mdef: untpd.Tree)(using Context): Unit =
     val annot = Annotations.Annotation(tree)
@@ -3335,7 +3337,8 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   end typedPackageDef
 
   def typedAnnotated(tree: untpd.Annotated, pt: Type)(using Context): Tree = {
-    val annot1 = checkAnnotClass(typedExpr(tree.annot))
+    val annot0 = withMode(Mode.InAnnotation)(typedExpr(tree.annot))
+    val annot1 = checkAnnotClass(annot0)
     val annotCls = Annotations.annotClass(annot1)
     if annotCls == defn.NowarnAnnot then
       registerNowarn(annot1, tree)

tests/printing/dependent-annot-default-args.check

@@ -23,15 +23,16 @@ package <empty> {
     new dependent-annot-default-args$package()
   final module class dependent-annot-default-args$package() extends Object() {
     this: dependent-annot-default-args$package.type =>
-    def f(x: Int): Int @annot(x) = x
+    def f(x: Any): Any @annot(x) = x
     def f2(x: Int):
       Int @annot2(
         y = Array.apply[Any](["Hello",x : Any]*)(scala.reflect.ClassTag.Any))
      = x
+    def f3(x: Any, y: Any): Any @annot(x = x, y = y) = x
     def test: Unit =
       {
         val y: Int = ???
-        val z: Int @annot(y) = f(y)
+        val z: Any @annot(y) = f(y)
         val z2:
           Int @annot2(
             y = Array.apply[Any](["Hello",y : Any]*)(scala.reflect.ClassTag.Any)
@@ -41,6 +42,78 @@ package <empty> {
         @annot2(
           y = Array.apply[Any](["Hello",y : Any]*)(scala.reflect.ClassTag.Any))
           val z4: Int = 45
+        val z5: annot =
+          {
+            val y$1: Array[String] =
+              Array.apply[String](["World" : String]*)(
+                scala.reflect.ClassTag.apply[String](classOf[String]))
+            new annot(x = 1, y = y$1)
+          }
+        val z6: annot2 =
+          {
+            val y$2: Array[Any] =
+              Array.apply[Any](["World" : Any]*)(scala.reflect.ClassTag.Any)
+            new annot2(x = 1, y = y$2)
+          }
+        @annot(x = 2,
+          y =
+            {
+              val y$3: Array[String] =
+                Array.apply[String](["World" : String]*)(
+                  scala.reflect.ClassTag.apply[String](classOf[String]))
+              new annot(x = 1, y = y$3)
+            }
+        ) val z7: Int = 45
+        @annot(x = 4,
+          y =
+            3:
+              Int @annot(x = 1,
+                y =
+                  Array.apply[String](["World" : String]*)(
+                    scala.reflect.ClassTag.apply[String](classOf[String]))
+              )
+        ) val z8: Int = 45
+        val z9:
+          Int @annot(x = 2,
+            y =
+              {
+                val y$4: Array[String] =
+                  Array.apply[String](["World" : String]*)(
+                    scala.reflect.ClassTag.apply[String](classOf[String]))
+                new annot(x = 1, y = y$4)
+              }
+          )
+         = 46
+        @annot(x = 4,
+          y =
+            3:
+              Int @annot(x = 1,
+                y =
+                  Array.apply[String](["World" : String]*)(
+                    scala.reflect.ClassTag.apply[String](classOf[String]))
+              )
+        ) val z10: Int = 45
+        val z11: Any @annot(annot) =
+          f(
+            {
+              val y$5: Array[String] =
+                Array.apply[String](["World" : String]*)(
+                  scala.reflect.ClassTag.apply[String](classOf[String]))
+              new annot(x = 1, y = y$5)
+            }
+          )
+        val z12: Any @annot(x = x, y = y) =
+          f3(
+            Array.apply[String](["World" : String]*)(
+              scala.reflect.ClassTag.apply[String](classOf[String])),
+          1)
+        val z13: Any @annot(x = x, y = y) =
+          {
+            val y$6: Array[String] =
+              Array.apply[String](["World" : String]*)(
+                scala.reflect.ClassTag.apply[String](classOf[String]))
+            f3(x = 1, y = y$6)
+          }
         ()
       }
   }

tests/printing/dependent-annot-default-args.scala

@@ -1,8 +1,9 @@
 class annot(x: Any, y: Any = 42) extends annotation.Annotation
 class annot2(x: Any = -1, y: Array[Any] = Array("Hello")) extends annotation.Annotation
 
-def f(x: Int): Int @annot(x) = x
+def f(x: Any): Any @annot(x) = x
 def f2(x: Int): Int @annot2(y = Array("Hello", x)) = x
+def f3(x: Any, y: Any): Any @annot(y=y, x=x) = x
 
 def test =
   val y: Int = ???
@@ -13,3 +14,14 @@ def test =
   @annot(44) val z3 = 45
   @annot2(y = Array("Hello", y)) val z4 = 45
 
+  // Arguments are still lifted if the annotation class is instantiated
+  // explicitly. See #22526.
+  val z5 = new annot(y = Array("World"), x = 1)
+  val z6 = new annot2(y = Array("World"), x = 1)
+  @annot(y = new annot(y = Array("World"), x = 1), x = 2) val z7 = 45
+  @annot(y = 3: Int @annot(y = Array("World"), x = 1), x = 4) val z8 = 45
+  val z9: Int @annot(y = new annot(y = Array("World"), x = 1), x = 2)  = 46
+  @annot(y = 3: Int @annot(y = Array("World"), x = 1), x = 4) val z10 = 45
+  val z11 = f(new annot(y = Array("World"), x = 1))
+  val z12 = f3(Array("World"), 1)
+  val z13 = f3(y=Array("World"), x=1)