Merge pull request #13474 from dotty-staging/dep-annots

Remove anomalies and gaps in handling annotations

Author: odersky

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

@@ -113,11 +113,11 @@ trait TreeInfo[T >: Untyped <: Type] { self: Trees.Instance[T] =>
     case _ => 0
   }
 
-  /** The (last) list of arguments of an application */
-  def arguments(tree: Tree): List[Tree] = unsplice(tree) match {
-    case Apply(_, args) => args
-    case TypeApply(fn, _) => arguments(fn)
-    case Block(_, expr) => arguments(expr)
+  /** All 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 Block(_, expr) => allArguments(expr)
     case _ => Nil
   }
 

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

@@ -7,14 +7,17 @@ import StdNames._
 import dotty.tools.dotc.ast.tpd
 import scala.util.Try
 import util.Spans.Span
+import printing.{Showable, Printer}
+import printing.Texts.Text
+import annotation.internal.sharable
 
 object Annotations {
 
   def annotClass(tree: Tree)(using Context) =
     if (tree.symbol.isConstructor) tree.symbol.owner
     else tree.tpe.typeSymbol
 
-  abstract class Annotation {
+  abstract class Annotation extends Showable {
     def tree(using Context): Tree
 
     def symbol(using Context): Symbol = annotClass(tree)
@@ -26,7 +29,8 @@ object Annotations {
     def derivedAnnotation(tree: Tree)(using Context): Annotation =
       if (tree eq this.tree) this else Annotation(tree)
 
-    def arguments(using Context): List[Tree] = ast.tpd.arguments(tree)
+    /** All arguments to this annotation in a single flat list */
+    def arguments(using Context): List[Tree] = ast.tpd.allArguments(tree)
 
     def argument(i: Int)(using Context): Option[Tree] = {
       val args = arguments
@@ -44,15 +48,48 @@ object Annotations {
     /** The tree evaluation has finished. */
     def isEvaluated: Boolean = true
 
+    /** Normally, type map over all tree nodes of this annotation, but can
+     *  be overridden. Returns EmptyAnnotation if type type map produces a range
+     *  type, since ranges cannot be types of trees.
+     */
+    def mapWith(tm: TypeMap)(using Context) =
+      val args = arguments
+      if args.isEmpty then this
+      else
+        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 =:= 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 this
+
+    /** Does this annotation refer to a parameter of `tl`? */
+    def refersToParamOf(tl: TermLambda)(using Context): Boolean =
+      val args = arguments
+      if args.isEmpty then false
+      else tree.existsSubTree {
+        case id: Ident => id.tpe match
+          case TermParamRef(tl1, _) => tl eq tl1
+          case _ => false
+        case _ => false
+      }
+
+    /** A string representation of the annotation. Overridden in BodyAnnotation.
+     */
+    def toText(printer: Printer): Text = printer.annotText(this)
+
     def ensureCompleted(using Context): Unit = tree
 
     def sameAnnotation(that: Annotation)(using Context): Boolean =
       symbol == that.symbol && tree.sameTree(that.tree)
   }
 
-  case class ConcreteAnnotation(t: Tree) extends Annotation {
+  case class ConcreteAnnotation(t: Tree) extends Annotation:
     def tree(using Context): Tree = t
-  }
 
   abstract class LazyAnnotation extends Annotation {
     protected var mySym: Symbol | (Context ?=> Symbol)
@@ -98,6 +135,7 @@ object Annotations {
       if (tree eq this.tree) this else ConcreteBodyAnnotation(tree)
     override def arguments(using Context): List[Tree] = Nil
     override def ensureCompleted(using Context): Unit = ()
+    override def toText(printer: Printer): Text = "@Body"
   }
 
   class ConcreteBodyAnnotation(body: Tree) extends BodyAnnotation {
@@ -194,6 +232,8 @@ object Annotations {
       apply(defn.SourceFileAnnot, Literal(Constant(path)))
   }
 
+  @sharable val EmptyAnnotation = Annotation(EmptyTree)
+
   def ThrowsAnnotation(cls: ClassSymbol)(using Context): Annotation = {
     val tref = cls.typeRef
     Annotation(defn.ThrowsAnnot.typeRef.appliedTo(tref), Ident(tref))

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

@@ -162,9 +162,13 @@ object TypeOps:
         // with Nulls (which have no base classes). Under -Yexplicit-nulls, we take
         // corrective steps, so no widening is wanted.
         simplify(l, theMap) | simplify(r, theMap)
-      case AnnotatedType(parent, annot)
-      if annot.symbol == defn.UncheckedVarianceAnnot && !ctx.mode.is(Mode.Type) && !theMap.isInstanceOf[SimplifyKeepUnchecked] =>
-        simplify(parent, theMap)
+      case tp @ AnnotatedType(parent, annot) =>
+        val parent1 = simplify(parent, theMap)
+        if annot.symbol == defn.UncheckedVarianceAnnot
+            && !ctx.mode.is(Mode.Type)
+            && !theMap.isInstanceOf[SimplifyKeepUnchecked]
+        then parent1
+        else tp.derivedAnnotatedType(parent1, annot)
       case _: MatchType =>
         val normed = tp.tryNormalize
         if (normed.exists) normed else mapOver

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

@@ -3604,6 +3604,9 @@ object Types {
           case tp: AppliedType => tp.fold(status, compute(_, _, theAcc))
           case tp: TypeVar if !tp.isInstantiated => combine(status, Provisional)
           case tp: TermParamRef if tp.binder eq thisLambdaType => TrueDeps
+          case AnnotatedType(parent, ann) =>
+            if ann.refersToParamOf(thisLambdaType) then TrueDeps
+            else compute(status, parent, theAcc)
           case _: ThisType | _: BoundType | NoPrefix => status
           case _ =>
             (if theAcc != null then theAcc else DepAcc()).foldOver(status, tp)
@@ -3656,8 +3659,10 @@ object Types {
       if (isResultDependent) {
         val dropDependencies = new ApproximatingTypeMap {
           def apply(tp: Type) = tp match {
-            case tp @ TermParamRef(thisLambdaType, _) =>
+            case tp @ TermParamRef(`thisLambdaType`, _) =>
               range(defn.NothingType, atVariance(1)(apply(tp.underlying)))
+            case AnnotatedType(parent, ann) if ann.refersToParamOf(thisLambdaType) =>
+              mapOver(parent)
             case _ => mapOver(tp)
           }
         }
@@ -5380,6 +5385,8 @@ object Types {
       variance = saved
       derivedLambdaType(tp)(ptypes1, this(restpe))
 
+    def isRange(tp: Type): Boolean = tp.isInstanceOf[Range]
+
     /** Map this function over given type */
     def mapOver(tp: Type): Type = {
       record(s"TypeMap mapOver ${getClass}")
@@ -5423,8 +5430,9 @@ object Types {
 
         case tp @ AnnotatedType(underlying, annot) =>
           val underlying1 = this(underlying)
-          if (underlying1 eq underlying) tp
-          else derivedAnnotatedType(tp, underlying1, mapOver(annot))
+          val annot1 = annot.mapWith(this)
+          if annot1 eq EmptyAnnotation then underlying1
+          else derivedAnnotatedType(tp, underlying1, annot1)
 
         case _: ThisType
           | _: BoundType
@@ -5496,9 +5504,6 @@ object Types {
       else newScopeWith(elems1: _*)
     }
 
-    def mapOver(annot: Annotation): Annotation =
-      annot.derivedAnnotation(mapOver(annot.tree))
-
     def mapOver(tree: Tree): Tree = treeTypeMap(tree)
 
     /** Can be overridden. By default, only the prefix is mapped. */
@@ -5545,8 +5550,6 @@ object Types {
 
     protected def emptyRange = range(defn.NothingType, defn.AnyType)
 
-    protected def isRange(tp: Type): Boolean = tp.isInstanceOf[Range]
-
     protected def lower(tp: Type): Type = tp match {
       case tp: Range => tp.lo
       case _ => tp

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -539,7 +539,10 @@ class PlainPrinter(_ctx: Context) extends Printer {
     case _ => literalText(String.valueOf(const.value))
   }
 
-  def toText(annot: Annotation): Text = s"@${annot.symbol.name}" // for now
+  /** Usual target for `Annotation#toText`, overridden in RefinedPrinter */
+  def annotText(annot: Annotation): Text = s"@${annot.symbol.name}"
+
+  def toText(annot: Annotation): Text = annot.toText(this)
 
   def toText(param: LambdaParam): Text =
     varianceSign(param.paramVariance)
@@ -570,7 +573,7 @@ class PlainPrinter(_ctx: Context) extends Printer {
         Text()
 
     nodeName ~ "(" ~ elems ~ tpSuffix ~ ")" ~ (Str(tree.sourcePos.toString) provided printDebug)
-  }.close // todo: override in refined printer
+  }.close
 
   def toText(pos: SourcePosition): Text =
     if (!pos.exists) "<no position>"

compiler/src/dotty/tools/dotc/printing/Printer.scala

@@ -119,6 +119,9 @@ abstract class Printer {
   /** A description of sym's location */
   def extendedLocationText(sym: Symbol): Text
 
+  /** Textual description of regular annotation in terms of its tree */
+  def annotText(annot: Annotation): Text
+
   /** Textual representation of denotation */
   def toText(denot: Denotation): Text
 

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -21,7 +21,7 @@ import typer.ProtoTypes._
 import Trees._
 import TypeApplications._
 import Decorators._
-import NameKinds.WildcardParamName
+import NameKinds.{WildcardParamName, DefaultGetterName}
 import util.Chars.isOperatorPart
 import transform.TypeUtils._
 import transform.SymUtils._
@@ -607,7 +607,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       case tree: Template =>
         toTextTemplate(tree)
       case Annotated(arg, annot) =>
-        toTextLocal(arg) ~~ annotText(annot)
+        toTextLocal(arg) ~~ toText(annot)
       case EmptyTree =>
         "<empty>"
       case TypedSplice(t) =>
@@ -964,14 +964,18 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
     keywordStr("package ") ~ toTextPackageId(tree.pid) ~ bodyText
   }
 
+  /** Textual representation of an instance creation expression without the leading `new` */
   protected def constrText(tree: untpd.Tree): Text = toTextLocal(tree).stripPrefix(keywordStr("new ")) // DD
 
-  protected def annotText(tree: untpd.Tree): Text = "@" ~ constrText(tree) // DD
-
-  override def annotsText(sym: Symbol): Text =
-    Text(sym.annotations.map(ann =>
-      if ann.symbol == defn.BodyAnnot then Str(simpleNameString(ann.symbol))
-      else annotText(ann.tree)))
+  protected def annotText(sym: Symbol, tree: untpd.Tree): Text =
+    def recur(t: untpd.Tree): Text = t match
+      case Apply(fn, Nil) => recur(fn)
+      case Apply(fn, args) =>
+        val explicitArgs = args.filterNot(_.symbol.name.is(DefaultGetterName))
+        recur(fn) ~ "(" ~ toTextGlobal(explicitArgs, ", ") ~ ")"
+      case TypeApply(fn, args) => recur(fn) ~ "[" ~ toTextGlobal(args, ", ") ~ "]"
+      case _ => s"@${sym.orElse(tree.symbol).name}"
+    recur(tree)
 
   protected def modText(mods: untpd.Modifiers, sym: Symbol, kw: String, isType: Boolean): Text = { // DD
     val suppressKw = if (enclDefIsClass) mods.isAllOf(LocalParam) else mods.is(Param)
@@ -984,12 +988,16 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
     if (rawFlags.is(Param)) flagMask = flagMask &~ Given &~ Erased
     val flags = rawFlags & flagMask
     var flagsText = toTextFlags(sym, flags)
-    val annotations =
-      if (sym.exists) sym.annotations.filterNot(ann => dropAnnotForModText(ann.symbol)).map(_.tree)
-      else mods.annotations.filterNot(tree => dropAnnotForModText(tree.symbol))
-    Text(annotations.map(annotText), " ") ~~ flagsText ~~ (Str(kw) provided !suppressKw)
+    val annotTexts =
+      if sym.exists then
+        sym.annotations.filterNot(ann => dropAnnotForModText(ann.symbol)).map(toText)
+      else
+        mods.annotations.filterNot(tree => dropAnnotForModText(tree.symbol)).map(annotText(NoSymbol, _))
+    Text(annotTexts, " ") ~~ flagsText ~~ (Str(kw) provided !suppressKw)
   }
 
+  override def annotText(annot: Annotation): Text = annotText(annot.symbol, annot.tree)
+
   def optText(name: Name)(encl: Text => Text): Text =
     if (name.isEmpty) "" else encl(toText(name))
 

tests/neg/annot-printing.check

@@ -0,0 +1,7 @@
+-- [E007] Type Mismatch Error: tests/neg/annot-printing.scala:5:46 -----------------------------------------------------
+5 |def x: Int @nowarn @main @Foo @Bar("hello") = "abc" // error
+  |                                              ^^^^^
+  |                                              Found:    ("abc" : String)
+  |                                              Required: Int @nowarn() @main @Foo @Bar("hello")
+
+longer explanation available when compiling with `-explain`

tests/neg/annot-printing.scala

@@ -0,0 +1,6 @@
+import scala.annotation.*
+class Foo() extends Annotation
+class Bar(s: String) extends Annotation
+
+def x: Int @nowarn @main @Foo @Bar("hello") = "abc" // error
+

tests/pos/dependent-annot.scala

@@ -0,0 +1,7 @@
+class C
+class ann(x: Any*) extends annotation.Annotation
+
+def f(y: C, z: C) =
+  def g(): C @ann(y, z) = ???
+  val ac: ((x: C) => Array[String @ann(x)]) = ???
+  val dc = ac(g())