Fix #15883: Interpret inner static object access as this access

compiler/src/dotty/tools/dotc/transform/init/Errors.scala

@@ -79,35 +79,35 @@ object Errors:
   override def toString() = this.getClass.getName.nn
 
   /** Access non-initialized field */
-  case class AccessNonInit(field: Symbol, trace: Seq[Tree]) extends Error:
+  case class AccessNonInit(field: Symbol)(val trace: Seq[Tree]) extends Error:
     def source: Tree = trace.last
     def show(using Context): String =
       "Access non-initialized " + field.show + "." + stacktrace
 
     override def pos(using Context): SourcePosition = field.sourcePos
 
   /** Promote a value under initialization to fully-initialized */
-  case class PromoteError(msg: String, trace: Seq[Tree]) extends Error:
+  case class PromoteError(msg: String)(val trace: Seq[Tree]) extends Error:
     def show(using Context): String = msg + stacktrace
 
-  case class AccessCold(field: Symbol, trace: Seq[Tree]) extends Error:
+  case class AccessCold(field: Symbol)(val trace: Seq[Tree]) extends Error:
     def show(using Context): String =
       "Access field " + field.show +  " on a cold object." + stacktrace
 
-  case class CallCold(meth: Symbol, trace: Seq[Tree]) extends Error:
+  case class CallCold(meth: Symbol)(val trace: Seq[Tree]) extends Error:
     def show(using Context): String =
       "Call method " + meth.show + " on a cold object." + stacktrace
 
-  case class CallUnknown(meth: Symbol, trace: Seq[Tree]) extends Error:
+  case class CallUnknown(meth: Symbol)(val trace: Seq[Tree]) extends Error:
     def show(using Context): String =
       val prefix = if meth.is(Flags.Method) then "Calling the external method " else "Accessing the external field"
       prefix + meth.show + " may cause initialization errors." + stacktrace
 
   /** Promote a value under initialization to fully-initialized */
-  case class UnsafePromotion(msg: String, trace: Seq[Tree], error: Error) extends Error:
+  case class UnsafePromotion(msg: String, error: Error)(val trace: Seq[Tree]) extends Error:
     def show(using Context): String =
       msg + stacktrace + "\n" +
-        "Promoting the value to hot failed due to the following problem:\n" + {
+        "Promoting the value to hot (transitively initialized) failed due to the following problem:\n" + {
           val ctx2 = ctx.withProperty(IsFromPromotion, Some(true))
           error.show(using ctx2)
         }
@@ -116,7 +116,7 @@ object Errors:
    *
    *  Invariant: argsIndices.nonEmpty
    */
-  case class UnsafeLeaking(trace: Seq[Tree], error: Error, nonHotOuterClass: Symbol, argsIndices: List[Int]) extends Error:
+  case class UnsafeLeaking(error: Error, nonHotOuterClass: Symbol, argsIndices: List[Int])(val trace: Seq[Tree]) extends Error:
     def show(using Context): String =
       "Problematic object instantiation: " + argumentInfo() + stacktrace + "\n" +
         "It leads to the following error during object initialization:\n" +
@@ -141,5 +141,5 @@ object Errors:
           acc + text2
         }
       val verb = if multiple then " are " else " is "
-      val adjective = "not hot."
+      val adjective = "not hot (transitively initialized)."
       subject + verb + adjective

compiler/src/dotty/tools/dotc/transform/init/Semantic.scala

@@ -156,7 +156,7 @@ object Semantic:
     def hasField(f: Symbol) = fields.contains(f)
 
   object Promoted:
-    class PromotionInfo:
+    class PromotionInfo(val entryClass: ClassSymbol):
       var isCurrentObjectPromoted: Boolean = false
       val values = mutable.Set.empty[Value]
       override def toString(): String = values.toString()
@@ -165,14 +165,15 @@ object Semantic:
     opaque type Promoted = PromotionInfo
 
     /** Note: don't use `val` to avoid incorrect sharing */
-    def empty: Promoted = new PromotionInfo
+    def empty(entryClass: ClassSymbol): Promoted = new PromotionInfo(entryClass)
 
     extension (promoted: Promoted)
       def isCurrentObjectPromoted: Boolean = promoted.isCurrentObjectPromoted
       def promoteCurrent(thisRef: ThisRef): Unit = promoted.isCurrentObjectPromoted = true
       def contains(value: Value): Boolean = promoted.values.contains(value)
       def add(value: Value): Unit = promoted.values += value
       def remove(value: Value): Unit = promoted.values -= value
+      def entryClass: ClassSymbol = promoted.entryClass
     end extension
   end Promoted
   type Promoted = Promoted.Promoted
@@ -658,12 +659,12 @@ object Semantic:
 
     def select(field: Symbol, receiver: Type, needResolve: Boolean = true): Contextual[Value] = log("select " + field.show + ", this = " + value, printer, (_: Value).show) {
       if promoted.isCurrentObjectPromoted then Hot
-      else value match {
+      else value match
         case Hot  =>
           Hot
 
         case Cold =>
-          val error = AccessCold(field, trace.toVector)
+          val error = AccessCold(field)(trace.toVector)
           reporter.report(error)
           Hot
 
@@ -688,11 +689,11 @@ object Semantic:
                 val rhs = target.defTree.asInstanceOf[ValOrDefDef].rhs
                 eval(rhs, ref, target.owner.asClass, cacheResult = true)
               else
-                val error = CallUnknown(field, trace.toVector)
+                val error = CallUnknown(field)(trace.toVector)
                 reporter.report(error)
                 Hot
             else
-              val error = AccessNonInit(target, trace.toVector)
+              val error = AccessNonInit(target)(trace.toVector)
               reporter.report(error)
               Hot
           else
@@ -710,7 +711,6 @@ object Semantic:
 
         case RefSet(refs) =>
           refs.map(_.select(field, receiver)).join
-      }
     }
 
     def call(meth: Symbol, args: List[ArgInfo], receiver: Type, superType: Type, needResolve: Boolean = true): Contextual[Value] = log("call " + meth.show + ", args = " + args.map(_.value.show), printer, (_: Value).show) {
@@ -779,7 +779,7 @@ object Semantic:
 
         case Cold =>
           promoteArgs()
-          val error = CallCold(meth, trace.toVector)
+          val error = CallCold(meth)(trace.toVector)
           reporter.report(error)
           Hot
 
@@ -820,7 +820,7 @@ object Semantic:
               // try promoting the receiver as last resort
               val hasErrors = Reporter.hasErrors { ref.promote("try promote value to hot") }
               if hasErrors then
-                val error = CallUnknown(target, trace.toVector)
+                val error = CallUnknown(target)(trace.toVector)
                 reporter.report(error)
               Hot
           else if target.exists then
@@ -899,7 +899,7 @@ object Semantic:
             Hot
           else
             // no source code available
-            val error = CallUnknown(ctor, trace.toVector)
+            val error = CallUnknown(ctor)(trace.toVector)
             reporter.report(error)
             Hot
       }
@@ -922,7 +922,7 @@ object Semantic:
             yield
               i + 1
 
-          val error = UnsafeLeaking(trace.toVector, errors.head, nonHotOuterClass, indices)
+          val error = UnsafeLeaking(errors.head, nonHotOuterClass, indices)(trace.toVector)
           reporter.report(error)
           Hot
         else
@@ -947,7 +947,7 @@ object Semantic:
             tryLeak(warm, NoSymbol, args2)
 
         case Cold =>
-          val error = CallCold(ctor, trace.toVector)
+          val error = CallCold(ctor)(trace.toVector)
           reporter.report(error)
           Hot
 
@@ -1078,15 +1078,15 @@ object Semantic:
         case Hot   =>
 
         case Cold  =>
-          reporter.report(PromoteError(msg, trace.toVector))
+          reporter.report(PromoteError(msg)(trace.toVector))
 
         case thisRef: ThisRef =>
           val emptyFields = thisRef.nonInitFields()
           if emptyFields.isEmpty then
             promoted.promoteCurrent(thisRef)
           else
             val fields = "Non initialized field(s): " + emptyFields.map(_.show).mkString(", ") + "."
-            reporter.report(PromoteError(msg + "\n" + fields, trace.toVector))
+            reporter.report(PromoteError(msg + "\n" + fields)(trace.toVector))
 
         case warm: Warm =>
           if !promoted.contains(warm) then
@@ -1106,7 +1106,7 @@ object Semantic:
               res.promote("The function return value is not hot. Found = " + res.show + ".")
             }
             if errors.nonEmpty then
-              reporter.report(UnsafePromotion(msg, trace.toVector, errors.head))
+              reporter.report(UnsafePromotion(msg, errors.head)(trace.toVector))
             else
               promoted.add(fun)
 
@@ -1156,7 +1156,7 @@ object Semantic:
         if !isHotSegment then
           for member <- klass.info.decls do
             if member.isClass then
-              val error = PromoteError("Promotion cancelled as the value contains inner " + member.show + ".", Vector.empty)
+              val error = PromoteError("Promotion cancelled as the value contains inner " + member.show + ".")(Vector.empty)
               reporter.report(error)
             else if !member.isType && !member.isConstructor  && !member.is(Flags.Deferred) then
               given Trace = Trace.empty
@@ -1189,7 +1189,7 @@ object Semantic:
       }
 
       if errors.isEmpty then Nil
-      else UnsafePromotion(msg, trace.toVector, errors.head) :: Nil
+      else UnsafePromotion(msg, errors.head)(trace.toVector) :: Nil
     }
 
   end extension
@@ -1230,7 +1230,7 @@ object Semantic:
 
       @tailrec
       def iterate(): Unit = {
-        given Promoted = Promoted.empty
+        given Promoted = Promoted.empty(thisRef.klass)
         given Trace = Trace.empty.add(thisRef.klass.defTree)
         given reporter: Reporter.BufferedReporter = new Reporter.BufferedReporter
 
@@ -1513,16 +1513,24 @@ object Semantic:
         thisV.accessLocal(tmref, klass)
 
       case tmref: TermRef =>
-        cases(tmref.prefix, thisV, klass).select(tmref.symbol, receiver = tmref.prefix)
+        val cls = tmref.widenSingleton.classSymbol
+        if cls.exists && cls.isStaticOwner then
+          if klass.isContainedIn(cls) then
+            resolveThis(cls.asClass, thisV, klass)
+          else if cls.isContainedIn(promoted.entryClass) then
+            cases(tmref.prefix, thisV, klass).select(tmref.symbol, receiver = tmref.prefix)
+          else
+            Hot
+        else
+          cases(tmref.prefix, thisV, klass).select(tmref.symbol, receiver = tmref.prefix)
 
       case tp @ ThisType(tref) =>
         val cls = tref.classSymbol.asClass
         if cls.isStaticOwner && !klass.isContainedIn(cls) then
           // O.this outside the body of the object O
           Hot
         else
-          val value = resolveThis(cls, thisV, klass)
-          value
+          resolveThis(cls, thisV, klass)
 
       case _: TermParamRef | _: RecThis  =>
         // possible from checking effects of types
@@ -1664,7 +1672,16 @@ object Semantic:
     if thisV.isThisRef || !thisV.asInstanceOf[Warm].isPopulatingParams then tpl.body.foreach {
       case vdef : ValDef if !vdef.symbol.is(Flags.Lazy) && !vdef.rhs.isEmpty =>
         val res = eval(vdef.rhs, thisV, klass)
-        thisV.updateField(vdef.symbol, res)
+        // TODO: Improve promotion to avoid handling enum initialization specially
+        //
+        // The failing case is tests/init/pos/i12544.scala due to promotion failure.
+        if vdef.symbol.name == nme.DOLLAR_VALUES
+           && vdef.symbol.is(Flags.Synthetic)
+           && vdef.symbol.owner.companionClass.is(Flags.Enum)
+        then
+          thisV.updateField(vdef.symbol, Hot)
+        else
+          thisV.updateField(vdef.symbol, res)
         fieldsChanged = true
 
       case _: MemberDef =>

tests/init/neg/closureLeak.check

@@ -8,7 +8,7 @@
    |              -> l.foreach(a => a.addX(this)) // error	[ closureLeak.scala:11 ]
    |                           ^^^^^^^^^^^^^^^^^
    |
-   |              Promoting the value to hot failed due to the following problem:
+   |              Promoting the value to hot (transitively initialized) failed due to the following problem:
    |              Cannot prove the method argument is hot. Only hot values are safe to leak.
    |              Found = ThisRef[class Outer].
    |              Non initialized field(s): value p. Promotion trace:

tests/init/neg/cycle-structure.check

@@ -1,7 +1,7 @@
 -- Error: tests/init/neg/cycle-structure.scala:3:13 --------------------------------------------------------------------
 3 |    val x = B(this)   // error
   |            ^^^^^^^
-  |            Problematic object instantiation: arg 1 is not hot. Calling trace:
+  |            Problematic object instantiation: arg 1 is not hot (transitively initialized). Calling trace:
   |            -> case class A(b: B) {	[ cycle-structure.scala:1 ]
   |               ^
   |            -> val x = B(this)   // error	[ cycle-structure.scala:3 ]
@@ -16,7 +16,7 @@
 -- Error: tests/init/neg/cycle-structure.scala:9:13 --------------------------------------------------------------------
 9 |    val x = A(this)   // error
   |            ^^^^^^^
-  |            Problematic object instantiation: arg 1 is not hot. Calling trace:
+  |            Problematic object instantiation: arg 1 is not hot (transitively initialized). Calling trace:
   |            -> case class B(a: A) {	[ cycle-structure.scala:7 ]
   |               ^
   |            -> val x = A(this)   // error	[ cycle-structure.scala:9 ]

tests/init/neg/i15363.check

@@ -1,7 +1,7 @@
 -- Error: tests/init/neg/i15363.scala:3:10 -----------------------------------------------------------------------------
 3 |  val b = new B(this) // error
   |          ^^^^^^^^^^^
-  |          Problematic object instantiation: arg 1 is not hot. Calling trace:
+  |          Problematic object instantiation: arg 1 is not hot (transitively initialized). Calling trace:
   |          -> class A:	[ i15363.scala:1 ]
   |             ^
   |          -> val b = new B(this) // error	[ i15363.scala:3 ]

tests/init/neg/i15883.scala

@@ -0,0 +1,2 @@
+val a = b
+val b = 1  // error

tests/init/neg/inherit-non-hot.check

@@ -11,7 +11,7 @@
   |        -> if b == null then b = new B(this) // error	[ inherit-non-hot.scala:6 ]
   |                             ^^^^^^^^^^^^^^^
   |
-  |        Promoting the value to hot failed due to the following problem:
+  |        Promoting the value to hot (transitively initialized) failed due to the following problem:
   |        Cannot prove that the field value a is hot. Found = Cold. Promotion trace:
   |        -> class B(a: A) {	[ inherit-non-hot.scala:10 ]
   |                   ^^^^

tests/init/neg/promotion-loop.check

@@ -8,7 +8,7 @@
    |          -> println(b)      // error	[ promotion-loop.scala:16 ]
    |                     ^
    |
-   |          Promoting the value to hot failed due to the following problem:
+   |          Promoting the value to hot (transitively initialized) failed due to the following problem:
    |          Cannot prove that the field value outer is hot. Found = ThisRef[class Test].
    |          Non initialized field(s): value n. Promotion trace:
    |          -> val outer = test	[ promotion-loop.scala:12 ]

tests/init/neg/promotion-segment3.check

@@ -8,5 +8,5 @@
   |      -> bar(new B)  // error	[ promotion-segment3.scala:9 ]
   |             ^^^^^
   |
-  |      Promoting the value to hot failed due to the following problem:
+  |      Promoting the value to hot (transitively initialized) failed due to the following problem:
   |      Promotion cancelled as the value contains inner class C.

tests/init/neg/secondary-ctor4.check

@@ -1,7 +1,7 @@
 -- Error: tests/init/neg/secondary-ctor4.scala:54:14 -------------------------------------------------------------------
 54 |      val c = new C(b, 5)   // error
    |              ^^^^^^^^^^^
-   |              Problematic object instantiation: arg 1 is not hot. Calling trace:
+   |              Problematic object instantiation: arg 1 is not hot (transitively initialized). Calling trace:
    |              -> class D {	[ secondary-ctor4.scala:52 ]
    |                 ^
    |              -> val c = new C(b, 5)   // error	[ secondary-ctor4.scala:54 ]
@@ -24,21 +24,21 @@
 -- Error: tests/init/neg/secondary-ctor4.scala:42:4 --------------------------------------------------------------------
 42 |    new A(new B(new D))  // error
    |    ^^^^^^^^^^^^^^^^^^^
-   |    Problematic object instantiation: the outer M.this and arg 1 are not hot. Calling trace:
-   |    -> class N(d: D) extends M(d) {	[ secondary-ctor4.scala:59 ]
-   |       ^
-   |    -> def this(d: D) = {	[ secondary-ctor4.scala:7 ]
-   |       ^
-   |    -> new A(new B(new D))  // error	[ secondary-ctor4.scala:42 ]
-   |       ^^^^^^^^^^^^^^^^^^^
+   |Problematic object instantiation: the outer M.this and arg 1 are not hot (transitively initialized). Calling trace:
+   |-> class N(d: D) extends M(d) {	[ secondary-ctor4.scala:59 ]
+   |   ^
+   |-> def this(d: D) = {	[ secondary-ctor4.scala:7 ]
+   |   ^
+   |-> new A(new B(new D))  // error	[ secondary-ctor4.scala:42 ]
+   |   ^^^^^^^^^^^^^^^^^^^
    |
-   |    It leads to the following error during object initialization:
-   |    Access field value n on a cold object. Calling trace:
-   |    -> def this(b: B) = {	[ secondary-ctor4.scala:17 ]
-   |       ^
-   |    -> Inner().foo()	[ secondary-ctor4.scala:26 ]
-   |       ^^^^^^^
-   |    -> class Inner() {	[ secondary-ctor4.scala:21 ]
-   |       ^
-   |    -> println(b.n)	[ secondary-ctor4.scala:23 ]
-   |               ^^^
+   |It leads to the following error during object initialization:
+   |Access field value n on a cold object. Calling trace:
+   |-> def this(b: B) = {	[ secondary-ctor4.scala:17 ]
+   |   ^
+   |-> Inner().foo()	[ secondary-ctor4.scala:26 ]
+   |   ^^^^^^^
+   |-> class Inner() {	[ secondary-ctor4.scala:21 ]
+   |   ^
+   |-> println(b.n)	[ secondary-ctor4.scala:23 ]
+   |           ^^^

tests/init/neg/t3273.check

@@ -8,7 +8,7 @@
   |              -> val num1: LazyList[Int] = 1 #:: num1.map(_ + 1)                        // error	[ t3273.scala:4 ]
   |                                                 ^^^^^^^^^^^^^^^
   |
-  |              Promoting the value to hot failed due to the following problem:
+  |              Promoting the value to hot (transitively initialized) failed due to the following problem:
   |              Access non-initialized value num1. Promotion trace:
   |              -> val num1: LazyList[Int] = 1 #:: num1.map(_ + 1)                        // error	[ t3273.scala:4 ]
   |                                                 ^^^^
@@ -22,7 +22,7 @@
   |              -> val num2: LazyList[Int] = 1 #:: num2.iterator.map(_ + 1).to(LazyList)  // error	[ t3273.scala:5 ]
   |                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
-  |              Promoting the value to hot failed due to the following problem:
+  |              Promoting the value to hot (transitively initialized) failed due to the following problem:
   |              Access non-initialized value num2. Promotion trace:
   |              -> val num2: LazyList[Int] = 1 #:: num2.iterator.map(_ + 1).to(LazyList)  // error	[ t3273.scala:5 ]
   |                                                 ^^^^