Support cleanup actions in class completers

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

@@ -14,6 +14,25 @@ import util.Spans.Span
 /** Operations that are shared between Namer and TreeUnpickler */
 object NamerOps:
 
+  /** A completer supporting cleanup actions.
+   *  Needed to break the loop between completion of class and companion object.
+   *  If we try to complete the class first, and completion needs the companion
+   *  object (for instance for processing an import) then the companion object
+   *  completion would consult the companion class info for constructor that
+   *  need a constructor proxy in the object. This can lead to a cyclic reference.
+   *  We break the cycle by delaying adding constructor proxies to be a cleanuo
+   *  action instead.
+   */
+  trait CompleterWithCleanup extends LazyType:
+    private var cleanupActions: List[() => Unit] = Nil
+    def addCleanupAction(op: () => Unit): Unit =
+      cleanupActions = op :: cleanupActions
+    def cleanup(): Unit =
+      if cleanupActions.nonEmpty then
+        cleanupActions.reverse.foreach(_())
+        cleanupActions = Nil
+  end CompleterWithCleanup
+
   /** The type of the constructed instance is returned
    *
    *  @param ctor the constructor
@@ -164,8 +183,14 @@ object NamerOps:
         ApplyProxyCompleter(constr),
         cls.privateWithin,
         constr.coord)
-    for dcl <- cls.info.decls do
+    def doAdd() = for dcl <- cls.info.decls do
       if dcl.isConstructor then scope.enter(proxy(dcl))
+    cls.infoOrCompleter match
+      case completer: CompleterWithCleanup if cls.is(Touched) =>
+        // Taking the info would lead to a cyclic reference here - delay instead until cleanup of `cls`
+        completer.addCleanupAction(doAdd)
+      case _ =>
+        doAdd()
     scope
   end addConstructorApplies
 

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

@@ -148,7 +148,8 @@ class TreeUnpickler(reader: TastyReader,
     }
   }
 
-  class Completer(reader: TastyReader)(using @constructorOnly _ctx: Context) extends LazyType {
+  class Completer(reader: TastyReader)(using @constructorOnly _ctx: Context)
+  extends LazyType, CompleterWithCleanup {
     import reader.*
     val owner = ctx.owner
     val mode = ctx.mode
@@ -168,6 +169,8 @@ class TreeUnpickler(reader: TastyReader,
             case ex: CyclicReference => throw ex
             case ex: AssertionError => fail(ex)
             case ex: Exception => fail(ex)
+          finally
+            cleanup()
   }
 
   class TreeReader(val reader: TastyReader) {
@@ -668,7 +671,7 @@ class TreeUnpickler(reader: TastyReader,
       val annotOwner =
         if sym.owner.isClass then newLocalDummy(sym.owner) else sym.owner
       var annots = annotFns.map(_(annotOwner))
-      if annots.exists(_.symbol == defn.SilentIntoAnnot) then
+      if annots.exists(_.hasSymbol(defn.SilentIntoAnnot)) then
         // Temporary measure until we can change TastyFormat to include an INTO tag
         sym.setFlag(Into)
         annots = annots.filterNot(_.symbol == defn.SilentIntoAnnot)

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

@@ -1141,7 +1141,8 @@ class Namer { typer: Typer =>
     end typeSig
   }
 
-  class ClassCompleter(cls: ClassSymbol, original: TypeDef)(ictx: Context) extends Completer(original)(ictx) {
+  class ClassCompleter(cls: ClassSymbol, original: TypeDef)(ictx: Context)
+  extends Completer(original)(ictx), CompleterWithCleanup {
     withDecls(newScope(using ictx))
 
     protected given completerCtx: Context = localContext(cls)
@@ -1764,6 +1765,7 @@ class Namer { typer: Typer =>
       processExports(using localCtx)
       defn.patchStdLibClass(cls)
       addConstructorProxies(cls)
+      cleanup()
     }
   }
 

tests/pos/i22436/atest.scala

@@ -0,0 +1,3 @@
+object Case1 {
+  def myProps(transport: ProtocolTransport): Unit = ???
+}

tests/pos/i22436/defs.scala

@@ -0,0 +1,7 @@
+object ProtocolTransport
+
+import ProtocolTransport.*
+
+@annotation.nowarn()
+class ProtocolTransport()
+