Check Java protected static in RefChecks

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

@@ -22,6 +22,7 @@ import config.Printers.refcheck
 import reporting.*
 import Constants.Constant
 import cc.stripCapturing
+import dotty.tools.dotc.printing.Formatting.hl
 
 object RefChecks {
   import tpd.*
@@ -1274,6 +1275,18 @@ object RefChecks {
         case tp: NamedType if tp.prefix.typeSymbol != ctx.owner.enclosingClass =>
           report.warning(UnqualifiedCallToAnyRefMethod(tree, tree.symbol), tree)
         case _ => ()
+
+  def checkJavaStaticProtected(tree: tpd.Apply | tpd.Select | tpd.Assign)(using Context): Unit =
+    val sym = tree.symbol
+    if sym.isAllOf(StaticProtected) then
+        val definedPackage = sym.enclosingPackageClass
+        val definedClass = sym.owner.companionClass //it's _not_ sym.enclosingClass because it's static, therefore enclosed in a companion object, not a class
+        val enclosingPackage = ctx.owner.enclosingPackageClass
+
+        if definedPackage != enclosingPackage && !ctx.owner.ownersIterator.exists(_.derivesFrom(definedClass)) then
+          report.error(em"${StaticProtected} $sym which is defined in $definedPackage is inaccessible at runtime from $enclosingPackage", tree.srcPos)
+  end checkJavaStaticProtected
+
 }
 import RefChecks.*
 
@@ -1363,6 +1376,15 @@ class RefChecks extends MiniPhase { thisPhase =>
   override def transformSelect(tree: tpd.Select)(using Context): tpd.Tree =
     if defn.ScalaBoxedClasses().contains(tree.qualifier.tpe.typeSymbol) && tree.name == nme.synchronized_ then
       report.warning(SynchronizedCallOnBoxedClass(tree), tree.srcPos)
+    checkJavaStaticProtected(tree)
+    tree
+
+  override def transformApply(tree: tpd.Apply)(using Context): tpd.Apply =
+    checkJavaStaticProtected(tree)
+    tree
+
+  override def transformAssign(tree: tpd.Assign)(using Context): tpd.Assign =
+    checkJavaStaticProtected(tree)
     tree
 }
 

tests/neg/i18446.check

@@ -0,0 +1,4 @@
+-- Error: tests/neg/i18446/Test.scala:1:17 -----------------------------------------------------------------------------
+1 |val _ = foo.Task.poll() // error
+  |        ^^^^^^^^^^^^^
+  |protected <java> <static> method poll which is defined in package foo is inaccessible at runtime from package <empty>

tests/neg/i18446/Task.java

@@ -0,0 +1,5 @@
+package foo;
+
+public abstract class Task{
+  protected static void poll(){ System.out.println("Task"); }
+}

tests/neg/i18446/Test.scala

@@ -0,0 +1 @@
+val _ = foo.Task.poll() // error

tests/run/i18446.check

@@ -0,0 +1,2 @@
+Task
+Task

tests/run/i18446/Client.scala

@@ -0,0 +1,7 @@
+// scalajs: --skip
+
+package bar;
+
+object Client extends foo.Task {
+  def run = foo.Task.poll()
+}

tests/run/i18446/Task.java

@@ -0,0 +1,5 @@
+package foo;
+
+public abstract class Task{
+  protected static void poll(){ System.out.println("Task"); }
+}

tests/run/i18446/Test.scala

@@ -0,0 +1,5 @@
+// scalajs: --skip
+
+@main def Test =
+    foo.run
+    bar.Client.run

tests/run/i18446/i18446.scala

@@ -0,0 +1,7 @@
+// scalajs: --skip
+
+package foo
+
+def run = {
+  foo.Task.poll()
+}