Add hasAttachment method

Author: odersky

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

@@ -9,9 +9,9 @@ import dotty.tools.dotc.core.TypeError
 import scala.annotation.tailrec
 
 /** A TreeMap that maintains the necessary infrastructure to support
- *  contxtual implicit searches (type-scope implicits are supported anyway).
+ *  contextual implicit searches (type-scope implicits are supported anyway).
  *
- *  This incudes impicits defined in scope as well as imported implicits.
+ *  This incudes implicits defined in scope as well as imported implicits.
  */
 class TreeMapWithImplicits extends tpd.TreeMap {
   import tpd._

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

@@ -437,7 +437,7 @@ object Trees {
     extends GenericApply[T] {
     type ThisTree[-T >: Untyped] = Apply[T]
 
-    def isGivenApply = getAttachment(untpd.ApplyGiven).nonEmpty
+    def isGivenApply = hasAttachment(untpd.ApplyGiven)
     def setGivenApply() = { pushAttachment(untpd.ApplyGiven, ()); this }
   }
 

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

@@ -298,7 +298,7 @@ object TypeTestsCasts {
 
         if (sym.isTypeTest) {
           val argType = tree.args.head.tpe
-          val isTrusted = tree.getAttachment(PatternMatcher.TrustedTypeTestKey).nonEmpty
+          val isTrusted = tree.hasAttachment(PatternMatcher.TrustedTypeTestKey)
           if (!isTrusted && !checkable(expr.tpe, argType, tree.span))
             ctx.warning(i"the type test for $argType cannot be checked at runtime", tree.sourcePos)
           transformTypeTest(expr, tree.args.head.tpe, flagUnrelated = true)

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

@@ -282,7 +282,7 @@ trait TypeAssigner {
    */
   def accessibleSelectionType(tree: untpd.RefTree, qual1: Tree)(implicit ctx: Context): Type = {
     val ownType = selectionType(tree, qual1)
-    if (tree.getAttachment(desugar.SuppressAccessCheck).isDefined) ownType
+    if (tree.hasAttachment(desugar.SuppressAccessCheck)) ownType
     else ensureAccessible(ownType, qual1.isInstanceOf[Super], tree.sourcePos)
   }
 

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

@@ -2437,7 +2437,7 @@ class Typer extends Namer
     }
 
     def isSyntheticApply(tree: Tree): Boolean = tree match {
-      case tree: Select => tree.getAttachment(InsertedApply).isDefined
+      case tree: Select => tree.hasAttachment(InsertedApply)
       case _ => false
     }
 
@@ -2459,7 +2459,7 @@ class Typer extends Namer
     else pt match {
       case pt @ FunProto(Nil, _)
       if tree.symbol.allOverriddenSymbols.exists(_.info.isNullaryMethod) &&
-         tree.getAttachment(DroppedEmptyArgs).isEmpty =>
+         !tree.hasAttachment(DroppedEmptyArgs) =>
         tree.putAttachment(DroppedEmptyArgs, ())
         pt.markAsDropped()
         tree

compiler/src/dotty/tools/dotc/util/Attachment.scala

@@ -23,6 +23,14 @@ object Attachment {
       else nx.getAttachment[V](key)
     }
 
+    /** Does an attachment corresponding to `key` exist? */
+    final def hasAttachment[V](key: Key[V]): Boolean = {
+      val nx = next
+      if (nx == null) false
+      else if (nx.key eq key) true
+      else nx.hasAttachment[V](key)
+    }
+
     /** The attachment corresponding to `key`.
      *  @throws NoSuchElementException  if no attachment with key exists
      */
@@ -107,7 +115,7 @@ object Attachment {
     }
 
     final def pushAttachment[V](key: Key[V], value: V): Unit = {
-      assert(!getAttachment(key).isDefined, s"duplicate attachment for key $key")
+      assert(!hasAttachment(key), s"duplicate attachment for key $key")
       next = new Link(key, value, next)
     }
 

compiler/test/dotty/tools/dotc/ast/AttachmentsTest.scala

@@ -51,9 +51,9 @@ class AttachmentsTests extends DottyTest {
 
         val copy = tpd.cpy.TypeDef(clazz)(rhs = tpd.EmptyTree)
         assertTrue("A copy should have been returned", clazz ne copy)
-        assertTrue("Attachment should be present", copy.getAttachment(StickyTestKey).isDefined)
-        assertTrue("Attachment shouldn't be present", copy.getAttachment(TestKey).isEmpty)
-        assertTrue("Attachment should be present", copy.getAttachment(StickyTestKey2).isDefined)
+        assertTrue("Attachment should be present", copy.hasAttachment(StickyTestKey))
+        assertTrue("Attachment shouldn't be present", !copy.hasAttachment(TestKey))
+        assertTrue("Attachment should be present", copy.hasAttachment(StickyTestKey2))
 
       case _ =>
         fail