Fix codegen for @static definitions

MoveStatics moves some of these definitions from the companion to the
corresponding class, but does not update the trees referencing these
definitions, so the qualifier type cannot be used as a receiver.

I think we need to seriously rethink how we handle static methods in the
compiler, but that would be a huge refactoring, so this commit just
patches the backend to special case `@static` methods to use the method
owner as receiver as was always done before this PR.

Author: smarter

compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala

@@ -439,8 +439,10 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
     /*
      * must-single-thread
      */
-    private def fieldOp(field: Symbol, isLoad: Boolean, hostClass: Symbol): Unit = {
-      val owner      = internalName(if (hostClass == null) field.owner else hostClass)
+    private def fieldOp(field: Symbol, isLoad: Boolean, specificReceiver: Symbol): Unit = {
+      val useSpecificReceiver = specificReceiver != null && !field.isScalaStatic
+
+      val owner      = internalName(if (useSpecificReceiver) specificReceiver else field.owner)
       val fieldJName = field.javaSimpleName.toString
       val fieldDescr = symInfoTK(field).descriptor
       val isStatic   = field.isStaticMember
@@ -1143,7 +1145,7 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
         if (specificReceiver != null)
           assert(style.isVirtual || specificReceiver == methodOwner, s"specificReceiver can only be specified for virtual calls. $method - $specificReceiver")
 
-        val useSpecificReceiver = specificReceiver != null && !specificReceiver.isBottomClass
+        val useSpecificReceiver = specificReceiver != null && !specificReceiver.isBottomClass && !method.isScalaStatic
         val receiver = if (useSpecificReceiver) specificReceiver else methodOwner
 
         // workaround for a JVM bug: https://bugs.openjdk.java.net/browse/JDK-8154587

compiler/src/dotty/tools/backend/jvm/BackendInterface.scala

@@ -491,6 +491,7 @@ abstract class BackendInterface extends BackendInterfaceDefinitions {
     def getsJavaPrivateFlag: Boolean
     def isFinal: Boolean
     def getsJavaFinalFlag: Boolean
+    def isScalaStatic: Boolean
     def isStaticMember: Boolean
     def isBottomClass: Boolean
     def isBridge: Boolean

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -678,8 +678,10 @@ class DottyBackendInterface(outputDirectory: AbstractFile, val superCallsMap: Ma
       isPrivate || (sym.isPrimaryConstructor && sym.owner.isTopLevelModuleClass)
 
     def isFinal: Boolean = sym.is(Flags.Final)
+    def isScalaStatic: Boolean =
+      toDenot(sym).hasAnnotation(ctx.definitions.ScalaStaticAnnot)
     def isStaticMember: Boolean = (sym ne NoSymbol) &&
-      (sym.is(Flags.JavaStatic) || toDenot(sym).hasAnnotation(ctx.definitions.ScalaStaticAnnot))
+      (sym.is(Flags.JavaStatic) || isScalaStatic)
       // guard against no sumbol cause this code is executed to select which call type(static\dynamic) to use to call array.clone
 
     def isBottomClass: Boolean = (sym eq defn.NullClass) || (sym eq defn.NothingClass)