Methods for filtering annotations carrying meta information.

Author: odersky

src/dotty/tools/dotc/core/SymDenotations.scala

@@ -215,6 +215,10 @@ object SymDenotations {
     final def transformAnnotations(f: Annotation => Annotation)(implicit ctx: Context): Unit =
       annotations = annotations.mapConserve(f)
 
+    /** Keep only those annotations that satisfy `p` */
+    final def filterAnnotations(p: Annotation => Boolean)(implicit ctx: Context): Unit =
+      annotations = annotations.filterConserve(p)
+
     /** Optionally, the annotation matching the given class symbol */
     final def getAnnotation(cls: Symbol)(implicit ctx: Context): Option[Annotation] =
       dropOtherAnnotations(annotations, cls) match {
@@ -230,9 +234,9 @@ object SymDenotations {
     final def removeAnnotation(cls: Symbol)(implicit ctx: Context): Unit =
       annotations = myAnnotations.filterNot(_ matches cls)
 
-    /** Copy all annotations from given symbol by adding them to this symbol */
-    final def addAnnotations(from: Symbol)(implicit ctx: Context): Unit =
-      from.annotations.foreach(addAnnotation)
+    /** Add all given annotations to this symbol */
+    final def addAnnotations(annots: TraversableOnce[Annotation])(implicit ctx: Context): Unit =
+      annots.foreach(addAnnotation)
 
     @tailrec
     private def dropOtherAnnotations(anns: List[Annotation], cls: Symbol)(implicit ctx: Context): List[Annotation] = anns match {

src/dotty/tools/dotc/transform/ExtensionMethods.scala

@@ -117,7 +117,7 @@ class ExtensionMethods extends MiniPhaseTransform with DenotTransformer with Ful
       imeth.flags | Final &~ (Override | Protected | AbsOverride),
       fullyParameterizedType(imeth.info, imeth.owner.asClass),
       privateWithin = imeth.privateWithin, coord = imeth.coord)
-    extensionMeth.addAnnotations(from = imeth)(ctx.withPhase(thisTransformer))
+    extensionMeth.addAnnotations(imeth.annotations)(ctx.withPhase(thisTransformer))
       // need to change phase to add tailrec annotation which gets removed from original method in the same phase.
     extensionMeth
   }

src/dotty/tools/dotc/transform/MixinOps.scala

@@ -19,7 +19,7 @@ class MixinOps(cls: ClassSymbol, thisTransform: DenotTransformer)(implicit ctx:
       name = member.name.stripScala2LocalSuffix,
       flags = member.flags &~ Deferred,
       info = cls.thisType.memberInfo(member)).enteredAfter(thisTransform).asTerm
-    res.addAnnotations(member)
+    res.addAnnotations(member.annotations)
     res
   }
 

src/dotty/tools/dotc/transform/SymUtils.scala

@@ -11,6 +11,7 @@ import Names._
 import StdNames._
 import NameOps._
 import Flags._
+import Annotations._
 import language.implicitConversions
 
 object SymUtils {
@@ -90,4 +91,12 @@ class SymUtils(val self: Symbol) extends AnyVal {
 
   def implClass(implicit ctx: Context): Symbol =
     self.owner.info.decl(self.name.implClassName).symbol
+
+  def annotationsCarrying(meta: ClassSymbol)(implicit ctx: Context): List[Annotation] =
+    self.annotations.filter(_.symbol.hasAnnotation(meta))
+
+  def withAnnotationsCarrying(from: Symbol, meta: ClassSymbol)(implicit ctx: Context): self.type = {
+    self.addAnnotations(from.annotationsCarrying(meta))
+    self
+  }
 }