Moved meta annotations to annotation.meta, plus.

It took me a long time to find a trivial error while adjusting the
annotation packages, so I spent even longer trying to make sure next
time it would take me less time. It's the usual business of eliminating
duplication and unnecessary indirection.

Behavioral note: there was no consistency or deducible reasoning
regarding when annotation checks would be performed against the
typeSymbol directly (thus excluding annotation subclasses) or when they
would do a subclass check. I saw no reason it shouldn't always be a
subclass check; if the annotation isn't supposed to be subclassed it
should be final, and if it is, then the subclasses had probably better
not stop exhibiting the behavior of the base class.

Example: this now draws deprecated warnings, but did not before.

  class bippy extends deprecated("hi mom", "burma shave")

  @bippy def f = 5

(The deprecation message isn't printed so we're not there yet, but
closer.)

There is some new internal documentation on annotations, sadly lacking
in my famous ascii diagrams, and some new conveniences. Review by rytz.

1 files changed, 55 insertions, 40 deletions

diff --git a/src/compiler/scala/reflect/internal/Definitions.scala b/src/compiler/scala/reflect/internal/Definitions.scala
index e3b149e0d6..d816ba247d 100644
--- a/src/compiler/scala/reflect/internal/Definitions.scala
+++ b/src/compiler/scala/reflect/internal/Definitions.scala
@@ -183,30 +183,6 @@ trait Definitions extends reflect.api.StandardDefinitions {
     lazy val ThrowableClass                 = getClass(sn.Throwable)
     lazy val UninitializedErrorClass        = getClass("scala.UninitializedFieldError")
 
-    // annotations
-    lazy val AnnotationClass            = getClass("scala.annotation.Annotation")
-    lazy val ClassfileAnnotationClass   = getClass("scala.annotation.ClassfileAnnotation")
-    lazy val StaticAnnotationClass      = getClass("scala.annotation.StaticAnnotation")
-    lazy val uncheckedStableClass       = getClass("scala.annotation.unchecked.uncheckedStable")
-    lazy val uncheckedVarianceClass     = getClass("scala.annotation.unchecked.uncheckedVariance")
-    lazy val UncheckedClass             = getClass("scala.unchecked")
-    lazy val ThrowsClass                = getClass("scala.throws")
-    lazy val TailrecClass               = getClass("scala.annotation.tailrec")
-    lazy val SwitchClass                = getClass("scala.annotation.switch")
-    lazy val ElidableMethodClass        = getClass("scala.annotation.elidable")
-    lazy val ImplicitNotFoundClass      = getClass("scala.annotation.implicitNotFound")
-    lazy val VarargsClass               = getClass("scala.annotation.varargs")
-    lazy val FieldTargetClass           = getClass("scala.beans.meta.field")
-    lazy val GetterTargetClass          = getClass("scala.beans.meta.getter")
-    lazy val SetterTargetClass          = getClass("scala.beans.meta.setter")
-    lazy val BeanGetterTargetClass      = getClass("scala.beans.meta.beanGetter")
-    lazy val BeanSetterTargetClass      = getClass("scala.beans.meta.beanSetter")
-    lazy val ParamTargetClass           = getClass("scala.beans.meta.param")
-    lazy val ScalaInlineClass           = getClass("scala.inline")
-    lazy val ScalaNoInlineClass         = getClass("scala.noinline")
-    lazy val SpecializedClass           = getClass("scala.specialized")
-    lazy val BridgeClass                = getClass("scala.annotation.bridge")
-
     // fundamental reference classes
     lazy val ScalaObjectClass           = getMember(ScalaPackageClass, tpnme.ScalaObject)
     lazy val PartialFunctionClass       = getClass("scala.PartialFunction")
@@ -256,6 +232,8 @@ trait Definitions extends reflect.api.StandardDefinitions {
     lazy val ArrowAssocClass  = getClass("scala.Predef.ArrowAssoc")
     lazy val StringAdd_+      = getMember(StringAddClass, nme.PLUS)
     lazy val NotNullClass     = getClass("scala.NotNull")
+    lazy val ScalaNumberClass           = getClass("scala.math.ScalaNumber")
+    lazy val TraitSetterAnnotationClass = getClass("scala.runtime.TraitSetter")
     lazy val DelayedInitClass = getClass("scala.DelayedInit")
       def delayedInitMethod = getMember(DelayedInitClass, nme.delayedInit)
       // a dummy value that communicates that a delayedInit call is compiler-generated
@@ -606,22 +584,59 @@ trait Definitions extends reflect.api.StandardDefinitions {
       def BoxedUnit_UNIT = getMember(BoxedUnitModule, "UNIT")
       def BoxedUnit_TYPE = getMember(BoxedUnitModule, "TYPE")
 
-    // special attributes
-    lazy val BeanPropertyAttr: Symbol           = getClass(sn.BeanProperty)
-    lazy val BooleanBeanPropertyAttr: Symbol    = getClass(sn.BooleanBeanProperty)
-    lazy val CloneableAttr: Symbol              = getClass("scala.cloneable")
-    lazy val DeprecatedAttr: Symbol             = getClass("scala.deprecated")
-    lazy val DeprecatedNameAttr: Symbol         = getClass("scala.deprecatedName")
-    lazy val MigrationAnnotationClass: Symbol   = getClass("scala.annotation.migration")
-    lazy val NativeAttr: Symbol                 = getClass("scala.native")
-    lazy val RemoteAttr: Symbol                 = getClass("scala.remote")
-    lazy val ScalaNumberClass: Symbol           = getClass("scala.math.ScalaNumber")
-    lazy val ScalaStrictFPAttr: Symbol          = getClass("scala.annotation.strictfp")
-    lazy val SerialVersionUIDAttr: Symbol       = getClass("scala.SerialVersionUID")
-    lazy val SerializableAttr: Symbol           = getClass("scala.annotation.serializable") // @serializable is deprecated
-    lazy val TraitSetterAnnotationClass: Symbol = getClass("scala.runtime.TraitSetter")
-    lazy val TransientAttr: Symbol              = getClass("scala.transient")
-    lazy val VolatileAttr: Symbol               = getClass("scala.volatile")
+    // Annotation base classes
+    lazy val AnnotationClass            = getClass("scala.annotation.Annotation")
+    lazy val ClassfileAnnotationClass   = getClass("scala.annotation.ClassfileAnnotation")
+    lazy val StaticAnnotationClass      = getClass("scala.annotation.StaticAnnotation")
+
+    // Annotations
+    lazy val BridgeClass                = getClass("scala.annotation.bridge")
+    lazy val ElidableMethodClass        = getClass("scala.annotation.elidable")
+    lazy val ImplicitNotFoundClass      = getClass("scala.annotation.implicitNotFound")
+    lazy val MigrationAnnotationClass   = getClass("scala.annotation.migration")
+    lazy val ScalaStrictFPAttr          = getClass("scala.annotation.strictfp")
+    lazy val SerializableAttr           = getClass("scala.annotation.serializable") // @serializable is deprecated
+    lazy val SwitchClass                = getClass("scala.annotation.switch")
+    lazy val TailrecClass               = getClass("scala.annotation.tailrec")
+    lazy val VarargsClass               = getClass("scala.annotation.varargs")
+    lazy val uncheckedStableClass       = getClass("scala.annotation.unchecked.uncheckedStable")
+    lazy val uncheckedVarianceClass     = getClass("scala.annotation.unchecked.uncheckedVariance")
+
+    lazy val BeanPropertyAttr           = getClass(sn.BeanProperty)
+    lazy val BooleanBeanPropertyAttr    = getClass(sn.BooleanBeanProperty)
+    lazy val CloneableAttr              = getClass("scala.cloneable")
+    lazy val DeprecatedAttr             = getClass("scala.deprecated")
+    lazy val DeprecatedNameAttr         = getClass("scala.deprecatedName")
+    lazy val NativeAttr                 = getClass("scala.native")
+    lazy val RemoteAttr                 = getClass("scala.remote")
+    lazy val ScalaInlineClass           = getClass("scala.inline")
+    lazy val ScalaNoInlineClass         = getClass("scala.noinline")
+    lazy val SerialVersionUIDAttr       = getClass("scala.SerialVersionUID")
+    lazy val SpecializedClass           = getClass("scala.specialized")
+    lazy val ThrowsClass                = getClass("scala.throws")
+    lazy val TransientAttr              = getClass("scala.transient")
+    lazy val UncheckedClass             = getClass("scala.unchecked")
+    lazy val VolatileAttr               = getClass("scala.volatile")
+
+    // Meta-annotations
+    lazy val BeanGetterTargetClass      = getMetaAnnotation("beanGetter")
+    lazy val BeanSetterTargetClass      = getMetaAnnotation("beanSetter")
+    lazy val FieldTargetClass           = getMetaAnnotation("field")
+    lazy val GetterTargetClass          = getMetaAnnotation("getter")
+    lazy val ParamTargetClass           = getMetaAnnotation("param")
+    lazy val SetterTargetClass          = getMetaAnnotation("setter")
+
+    private def getMetaAnnotation(name: String) = getClass("scala.annotation.meta." + name)
+    def isMetaAnnotation(sym: Symbol): Boolean = metaAnnotations(sym) || (
+      // Trying to allow for deprecated locations
+      sym.isAliasType && isMetaAnnotation(sym.info.typeSymbol)
+    )
+
+    lazy val metaAnnotations = Set(
+      FieldTargetClass, ParamTargetClass,
+      GetterTargetClass, SetterTargetClass,
+      BeanGetterTargetClass, BeanSetterTargetClass
+    )
 
     lazy val AnnotationDefaultAttr: Symbol = {
       val attr = newClass(RuntimePackageClass, tpnme.AnnotationDefaultATTR, List(AnnotationClass.typeConstructor))