Add capture checking attributes to TASTy (#19033)

Replace `@CaptureChecked` and `@WithPureFuns` with TASTy attributes.

Author: odersky

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

@@ -1038,8 +1038,6 @@ class Definitions {
   @tu lazy val UncheckedVarianceAnnot: ClassSymbol = requiredClass("scala.annotation.unchecked.uncheckedVariance")
   @tu lazy val UncheckedCapturesAnnot: ClassSymbol = requiredClass("scala.annotation.unchecked.uncheckedCaptures")
   @tu lazy val VolatileAnnot: ClassSymbol = requiredClass("scala.volatile")
-  @tu lazy val WithPureFunsAnnot: ClassSymbol = requiredClass("scala.annotation.internal.WithPureFuns")
-  @tu lazy val CaptureCheckedAnnot: ClassSymbol = requiredClass("scala.annotation.internal.CaptureChecked")
   @tu lazy val BeanGetterMetaAnnot: ClassSymbol = requiredClass("scala.annotation.meta.beanGetter")
   @tu lazy val BeanSetterMetaAnnot: ClassSymbol = requiredClass("scala.annotation.meta.beanSetter")
   @tu lazy val FieldMetaAnnot: ClassSymbol = requiredClass("scala.annotation.meta.field")
@@ -2004,7 +2002,7 @@ class Definitions {
   @tu lazy val ccExperimental: Set[Symbol] = Set(
     CapsModule, CapsModule.moduleClass, PureClass,
     CapabilityAnnot, RequiresCapabilityAnnot,
-    RetainsAnnot, RetainsByNameAnnot, WithPureFunsAnnot)
+    RetainsAnnot, RetainsByNameAnnot)
 
   // ----- primitive value class machinery ------------------------------------------
 

compiler/src/dotty/tools/dotc/core/tasty/Attributes.scala

@@ -9,16 +9,22 @@ class Attributes private[tasty](
 ) {
   def scala2StandardLibrary: Boolean = booleanTags(SCALA2STANDARDLIBRARYattr)
   def explicitNulls: Boolean = booleanTags(EXPLICITNULLSattr)
+  def captureChecked: Boolean = booleanTags(CAPTURECHECKEDattr)
+  def withPureFuns: Boolean = booleanTags(WITHPUREFUNSattr)
 }
 
 object Attributes:
   def apply(
     scala2StandardLibrary: Boolean,
     explicitNulls: Boolean,
+    captureChecked: Boolean,
+    withPureFuns: Boolean,
   ): Attributes =
     val booleanTags = BitSet.newBuilder
     if scala2StandardLibrary then booleanTags += SCALA2STANDARDLIBRARYattr
     if explicitNulls then booleanTags += EXPLICITNULLSattr
+    if captureChecked then booleanTags += CAPTURECHECKEDattr
+    if withPureFuns then booleanTags += WITHPUREFUNSattr
     new Attributes(booleanTags.result())
   end apply
 

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -92,11 +92,9 @@ class TreeUnpickler(reader: TastyReader,
   /** The root owner tree. See `OwnerTree` class definition. Set by `enterTopLevel`. */
   private var ownerTree: OwnerTree = uninitialized
 
-  /** Was unpickled class compiled with pureFunctions? */
-  private var withPureFuns: Boolean = false
-
   /** Was unpickled class compiled with capture checks? */
-  private var withCaptureChecks: Boolean = false
+  private val withCaptureChecks: Boolean =
+    attributeUnpicklerOpt.exists(_.attributes.captureChecked)
 
   private val unpicklingScala2Library =
     attributeUnpicklerOpt.exists(_.attributes.scala2StandardLibrary)
@@ -655,13 +653,8 @@ class TreeUnpickler(reader: TastyReader,
       }
       registerSym(start, sym)
       if (isClass) {
-        if sym.owner.is(Package) then
-          if annots.exists(_.hasSymbol(defn.CaptureCheckedAnnot)) then
-            sym.setFlag(CaptureChecked)
-            withCaptureChecks = true
-            withPureFuns = true
-          else if annots.exists(_.hasSymbol(defn.WithPureFunsAnnot)) then
-            withPureFuns = true
+        if sym.owner.is(Package) && withCaptureChecks then
+          sym.setFlag(CaptureChecked)
         sym.completer.withDecls(newScope)
         forkAt(templateStart).indexTemplateParams()(using localContext(sym))
       }

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

@@ -7,6 +7,7 @@ import Contexts.*
 import Decorators.*
 import tasty.*
 import config.Printers.{noPrinter, pickling}
+import config.Feature
 import java.io.PrintStream
 import Periods.*
 import Phases.*
@@ -111,6 +112,8 @@ class Pickler extends Phase {
           val attributes = Attributes(
             scala2StandardLibrary = ctx.settings.YcompileScala2Library.value,
             explicitNulls = ctx.settings.YexplicitNulls.value,
+            captureChecked = Feature.ccEnabled,
+            withPureFuns = Feature.pureFunsEnabled,
           )
           AttributePickler.pickleAttributes(attributes, pickler, scratch.attributeBuffer)
 

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

@@ -423,11 +423,6 @@ class PostTyper extends MacroTransform with InfoTransformer { thisPhase =>
                 val reference = ctx.settings.sourceroot.value
                 val relativePath = util.SourceFile.relativePath(ctx.compilationUnit.source, reference)
                 sym.addAnnotation(Annotation.makeSourceFile(relativePath, tree.span))
-              if sym != defn.WithPureFunsAnnot && sym != defn.CaptureCheckedAnnot then
-                if Feature.ccEnabled then
-                  sym.addAnnotation(Annotation(defn.CaptureCheckedAnnot, tree.span))
-                else if Feature.pureFunsEnabled then
-                  sym.addAnnotation(Annotation(defn.WithPureFunsAnnot, tree.span))
           else
             if !sym.is(Param) && !sym.owner.isOneOf(AbstractOrTrait) then
               Checking.checkGoodBounds(tree.symbol)

tasty/src/dotty/tools/tasty/TastyFormat.scala

@@ -273,6 +273,8 @@ Standard Section: "Attributes" Attribute*
 ```none
   Attribute     = SCALA2STANDARDLIBRARYattr
                   EXPLICITNULLSattr
+                  CAPTURECHECKEDattr
+                  WITHPUREFUNSattr
 ```
 
 **************************************************************************************/
@@ -611,6 +613,8 @@ object TastyFormat {
 
   final val SCALA2STANDARDLIBRARYattr = 1
   final val EXPLICITNULLSattr = 2
+  final val CAPTURECHECKEDattr = 3
+  final val WITHPUREFUNSattr = 4
 
   /** Useful for debugging */
   def isLegalTag(tag: Int): Boolean =
@@ -830,6 +834,8 @@ object TastyFormat {
   def attributeTagToString(tag: Int): String = tag match {
     case SCALA2STANDARDLIBRARYattr => "SCALA2STANDARDLIBRARYattr"
     case EXPLICITNULLSattr => "EXPLICITNULLSattr"
+    case CAPTURECHECKEDattr => "CAPTURECHECKEDattr"
+    case WITHPUREFUNSattr => "WITHPUREFUNSattr"
   }
 
   /** @return If non-negative, the number of leading references (represented as nats) of a length/trees entry.