Use more RetainingAnnotation tests where it makes sense

Author: odersky

compiler/src/dotty/tools/dotc/cc/CaptureOps.scala

@@ -661,7 +661,7 @@ class PathSelectionProto(val select: Select, val pt: Type) extends typer.ProtoTy
  */
 class CleanupRetains(using Context) extends TypeMap:
   def apply(tp: Type): Type = tp match
-    case AnnotatedType(parent, annot) if annot.symbol.isRetainsLike =>
+    case AnnotatedType(parent, annot: RetainingAnnotation) =>
       if Feature.ccEnabled then
         if annot.symbol == defn.RetainsAnnot || annot.symbol == defn.RetainsByNameAnnot then
           RetainingType(parent, defn.NothingType, byName = annot.symbol == defn.RetainsByNameAnnot)

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

@@ -24,7 +24,7 @@ import collection.mutable
 import ProtoTypes.*
 import staging.StagingLevel
 import inlines.Inlines.inInlineMethod
-import cc.{isRetainsLike, CaptureAnnotation}
+import cc.RetainingAnnotation
 
 import dotty.tools.backend.jvm.DottyBackendInterface.symExtensions
 
@@ -187,7 +187,7 @@ object TreeChecker {
         case tp: TypeVar =>
           assert(tp.isInstantiated, s"Uninstantiated type variable: ${tp.show}, tree = ${tree.show}")
           apply(tp.underlying)
-        case tp @ AnnotatedType(underlying, annot) if annot.symbol.isRetainsLike && !annot.isInstanceOf[CaptureAnnotation] =>
+        case tp @ AnnotatedType(underlying, annot: RetainingAnnotation) =>
           val underlying1 = this(underlying)
           val annot1 = insideRetainingAnnot:
             annot.mapWith(this)

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

@@ -26,6 +26,7 @@ import Nullables.*, NullOpsDecorator.*
 import config.{Feature, MigrationVersion, SourceVersion}
 import util.Property
 import util.chaining.tap
+import inlines.Inlines
 
 import collection.mutable
 import config.Printers.{overload, typr, unapp}
@@ -38,8 +39,6 @@ import annotation.threadUnsafe
 
 import scala.annotation.tailrec
 import scala.util.control.NonFatal
-import dotty.tools.dotc.cc.isRetains
-import dotty.tools.dotc.inlines.Inlines
 
 object Applications {
   import tpd.*

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

@@ -37,7 +37,7 @@ import config.Feature, Feature.{sourceVersion, modularity}
 import config.SourceVersion.*
 import config.MigrationVersion
 import printing.Formatting.hlAsKeyword
-import cc.{isCaptureChecking, isRetainsLike}
+import cc.{isCaptureChecking, RetainingAnnotation}
 import cc.Mutability.isUpdateMethod
 
 import collection.mutable
@@ -815,7 +815,7 @@ object Checking {
             declaredParents =
               tp.declaredParents.map(p => transformedParent(apply(p)))
             )
-        case tp @ AnnotatedType(underlying, annot) if annot.symbol.isRetainsLike =>
+        case tp @ AnnotatedType(underlying, annot: RetainingAnnotation) =>
           val underlying1 = this(underlying)
           val saved = inCaptureSet
           inCaptureSet = true