Merge pull request #1226 from dotty-staging/static-fixes

Multiple fixes to @static

17 files changed, 174 insertions, 34 deletions

diff --git a/src/dotty/runtime/LazyVals.scala b/src/dotty/runtime/LazyVals.scala
index f09e96f57..4dea0d34d 100644
--- a/src/dotty/runtime/LazyVals.scala
+++ b/src/dotty/runtime/LazyVals.scala
@@ -10,14 +10,24 @@ object LazyVals {
 
   final val BITS_PER_LAZY_VAL = 2L
   final val LAZY_VAL_MASK = 3L
+  final val debug = false
 
-  @inline def STATE(cur: Long, ord: Int) = (cur >> (ord * BITS_PER_LAZY_VAL)) & LAZY_VAL_MASK
+  @inline def STATE(cur: Long, ord: Int) = {
+    val r = (cur >> (ord * BITS_PER_LAZY_VAL)) & LAZY_VAL_MASK
+    if (debug)
+      println(s"STATE($cur, $ord) = $r")
+    r
+  }
   @inline def CAS(t: Object, offset: Long, e: Long, v: Int, ord: Int) = {
+    if (debug)
+      println(s"CAS($t, $offset, $e, $v, $ord)")
     val mask = ~(LAZY_VAL_MASK << ord * BITS_PER_LAZY_VAL)
     val n = (e & mask) | (v << (ord * BITS_PER_LAZY_VAL))
     compareAndSet(t, offset, e, n)
   }
   @inline def setFlag(t: Object, offset: Long, v: Int, ord: Int) = {
+    if (debug)
+      println(s"setFlag($t, $offset, $v, $ord)")
     var retry = true
     while (retry) {
       val cur = get(t, offset)
@@ -35,6 +45,8 @@ object LazyVals {
     }
   }
   @inline def wait4Notification(t: Object, offset: Long, cur: Long, ord: Int) = {
+    if (debug)
+      println(s"wait4Notification($t, $offset, $cur, $ord)")
     var retry = true
     while (retry) {
       val cur = get(t, offset)
@@ -51,7 +63,11 @@ object LazyVals {
   }
 
   @inline def compareAndSet(t: Object, off: Long, e: Long, v: Long) = unsafe.compareAndSwapLong(t, off, e, v)
-  @inline def get(t: Object, off: Long) = unsafe.getLongVolatile(t, off)
+  @inline def get(t: Object, off: Long) = {
+    if (debug)
+      println(s"get($t, $off)")
+    unsafe.getLongVolatile(t, off)
+  }
 
   val processors: Int = java.lang.Runtime.getRuntime.availableProcessors()
   val base: Int = 8 * processors * processors
@@ -68,7 +84,12 @@ object LazyVals {
     monitors(id)
   }
 
-  @inline def getOffset(clz: Class[_], name: String) = unsafe.objectFieldOffset(clz.getDeclaredField(name))
+  @inline def getOffset(clz: Class[_], name: String) = {
+    val r = unsafe.objectFieldOffset(clz.getDeclaredField(name))
+    if (debug)
+      println(s"getOffset($clz, $name) = $r")
+    r
+  }
 
   object Names {
     final val state = "STATE"
diff --git a/src/dotty/tools/backend/jvm/DottyBackendInterface.scala b/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
index 002a6bf27..23073d317 100644
--- a/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
+++ b/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
@@ -12,7 +12,7 @@ import scala.collection.generic.Clearable
 import scala.collection.mutable
 import scala.reflect.ClassTag
 import scala.reflect.internal.util.WeakHashSet
-import scala.reflect.io.{Directory, PlainDirectory, AbstractFile}
+import scala.reflect.io.{AbstractFile, Directory, PlainDirectory}
 import scala.tools.asm.{AnnotationVisitor, ClassVisitor, FieldVisitor, MethodVisitor}
 import scala.tools.nsc.backend.jvm.{BCodeHelpers, BackendInterface}
 import dotty.tools.dotc.core._
@@ -24,13 +24,16 @@ import Symbols._
 import Denotations._
 import Phases._
 import java.lang.AssertionError
-import dotty.tools.dotc.util.{Positions, DotClass}
+
+import dotty.tools.dotc.util.{DotClass, Positions}
 import Decorators._
 import tpd._
+
 import scala.tools.asm
 import NameOps._
 import StdNames.nme
 import NameOps._
+import dotty.tools.dotc.core
 
 class DottyBackendInterface(outputDirectory: AbstractFile)(implicit ctx: Context) extends BackendInterface{
   type Symbol          = Symbols.Symbol
@@ -633,7 +636,7 @@ class DottyBackendInterface(outputDirectory: AbstractFile)(implicit ctx: Context
         toDenot(sym)(shiftedContext).isStatic(shiftedContext)
       }
 
-    def isStaticConstructor: Boolean = isStaticMember && isClassConstructor
+    def isStaticConstructor: Boolean = (isStaticMember && isClassConstructor) || (sym.name eq core.Names.STATIC_CONSTRUCTOR)
 
 
     // navigation
@@ -716,7 +719,7 @@ class DottyBackendInterface(outputDirectory: AbstractFile)(implicit ctx: Context
       toDenot(sym).info.decls.filter(p => p.isTerm && !p.is(Flags.Method)).toList
     }
     def methodSymbols: List[Symbol] =
-      for (f <- toDenot(sym).info.decls.toList if !f.isMethod && f.isTerm && !f.isModule) yield f
+      for (f <- toDenot(sym).info.decls.toList if f.isMethod && f.isTerm && !f.isModule) yield f
     def serialVUID: Option[Long] = None
 
 
diff --git a/src/dotty/tools/dotc/Compiler.scala b/src/dotty/tools/dotc/Compiler.scala
index 2ddd81718..3844f42a7 100644
--- a/src/dotty/tools/dotc/Compiler.scala
+++ b/src/dotty/tools/dotc/Compiler.scala
@@ -91,6 +91,7 @@ class Compiler {
            new RestoreScopes),      // Repair scopes rendered invalid by moving definitions in prior phases of the group
       List(new ExpandPrivate,       // Widen private definitions accessed from nested classes
            new CollectEntryPoints,  // Find classes with main methods
+           new MoveStatics,         // Move static methods to companion classes
            new LabelDefs),          // Converts calls to labels to jumps
       List(new GenSJSIR),           // Generate .js code
       List(new GenBCode)            // Generate JVM bytecode
diff --git a/src/dotty/tools/dotc/core/NameOps.scala b/src/dotty/tools/dotc/core/NameOps.scala
index 72f89aec3..17af899e9 100644
--- a/src/dotty/tools/dotc/core/NameOps.scala
+++ b/src/dotty/tools/dotc/core/NameOps.scala
@@ -63,6 +63,7 @@ object NameOps {
       (if (name.isTermName) n.toTermName else n.toTypeName).asInstanceOf[N]
 
     def isConstructorName = name == CONSTRUCTOR || name == TRAIT_CONSTRUCTOR
+    def isStaticConstructorName = name == STATIC_CONSTRUCTOR
     def isExceptionResultName = name startsWith EXCEPTION_RESULT_PREFIX
     def isImplClassName = name endsWith IMPL_CLASS_SUFFIX
     def isLocalDummyName = name startsWith LOCALDUMMY_PREFIX
diff --git a/src/dotty/tools/dotc/core/Names.scala b/src/dotty/tools/dotc/core/Names.scala
index 223d95045..11f0b55a8 100644
--- a/src/dotty/tools/dotc/core/Names.scala
+++ b/src/dotty/tools/dotc/core/Names.scala
@@ -335,6 +335,7 @@ object Names {
 
   // can't move CONSTRUCTOR/EMPTY_PACKAGE to `nme` because of bootstrap failures in `encode`.
   val CONSTRUCTOR = termName("<init>")
+  val STATIC_CONSTRUCTOR = termName("<clinit>")
   val EMPTY_PACKAGE = termName("<empty>")
 
   val dontEncode = Set(CONSTRUCTOR, EMPTY_PACKAGE)
diff --git a/src/dotty/tools/dotc/core/SymDenotations.scala b/src/dotty/tools/dotc/core/SymDenotations.scala
index ff99f3b55..5c4e120a8 100644
--- a/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -594,6 +594,10 @@ object SymDenotations {
     final def isPrimaryConstructor(implicit ctx: Context) =
       isConstructor && owner.primaryConstructor == symbol
 
+    /** Does this symbol denote the static constructor of its enclosing class? */
+    final def isStaticConstructor(implicit ctx: Context) =
+      name.isStaticConstructorName
+
     /** Is this a subclass of the given class `base`? */
     def isSubClass(base: Symbol)(implicit ctx: Context) = false
 
@@ -1001,7 +1005,7 @@ object SymDenotations {
       if (!canMatchInheritedSymbols) Iterator.empty
       else overriddenFromType(owner.info)
 
-    /** Returns all all matching symbols defined in parents of the selftype. */
+    /** Returns all matching symbols defined in parents of the selftype. */
     final def extendedOverriddenSymbols(implicit ctx: Context): Iterator[Symbol] =
       if (!canMatchInheritedSymbols) Iterator.empty
       else overriddenFromType(owner.asClass.classInfo.selfType)
@@ -1499,7 +1503,7 @@ object SymDenotations {
 
     /** Enter a symbol in given `scope` without potentially replacing the old copy. */
     def enterNoReplace(sym: Symbol, scope: MutableScope)(implicit ctx: Context): Unit = {
-      require((sym.denot.flagsUNSAFE is Private) ||  !(this is Frozen) || (scope ne this.unforcedDecls))
+      require((sym.denot.flagsUNSAFE is Private) ||  !(this is Frozen) || (scope ne this.unforcedDecls) || sym.hasAnnotation(defn.ScalaStaticAnnot))
       scope.enter(sym)
 
       if (myMemberFingerPrint != FingerPrint.unknown)
diff --git a/src/dotty/tools/dotc/transform/CheckStatic.scala b/src/dotty/tools/dotc/transform/CheckStatic.scala
index 77c6dfc51..937a4f1cc 100644
--- a/src/dotty/tools/dotc/transform/CheckStatic.scala
+++ b/src/dotty/tools/dotc/transform/CheckStatic.scala
@@ -32,6 +32,7 @@ import TypeUtils._
   *     is not allowed to inherit classes that define a term member with name `foo`.
   *  5. Only `@static` methods and vals are supported in companions of traits.
   *     Java8 supports those, but not vars, and JavaScript does not have interfaces at all.
+  *  6. `@static` Lazy vals are currently unsupported.
   */
 class CheckStatic extends MiniPhaseTransform { thisTransformer =>
   import ast.tpd._
@@ -57,17 +58,18 @@ class CheckStatic extends MiniPhaseTransform { thisTransformer =>
         }
 
         val companion = ctx.owner.companionClass
-        if (!companion.exists) {
-          ctx.error("object that conatin @static members should have companion class", defn.pos)
-        }
+        def clashes = companion.asClass.membersNamed(defn.name)
 
-        val clashes = companion.asClass.membersNamed(defn.name)
-        if (clashes.exists) {
+        if (!companion.exists) {
+          ctx.error("object that contains @static members should have companion class", defn.pos)
+        } else if (clashes.exists) {
           ctx.error("companion classes cannot define members with same name as @static member", defn.pos)
-        }
-
-        if (defn.symbol.is(Flags.Mutable) && companion.is(Flags.Trait)) {
-          ctx.error("Companions of traits cannot define mutable @static fields")
+         } else if (defn.symbol.is(Flags.Mutable) && companion.is(Flags.Trait)) {
+          ctx.error("Companions of traits cannot define mutable @static fields", defn.pos)
+        } else if (defn.symbol.is(Flags.Lazy)) {
+          ctx.error("Lazy @static fields are not supported", defn.pos)
+        } else if (defn.symbol.allOverriddenSymbols.nonEmpty) {
+          ctx.error("@static members cannot override or implement non-static ones", defn.pos)
         }
       } else hadNonStaticField = hadNonStaticField || defn.isInstanceOf[ValDef]
 
diff --git a/src/dotty/tools/dotc/transform/Constructors.scala b/src/dotty/tools/dotc/transform/Constructors.scala
index 44638ce48..db850e944 100644
--- a/src/dotty/tools/dotc/transform/Constructors.scala
+++ b/src/dotty/tools/dotc/transform/Constructors.scala
@@ -91,7 +91,7 @@ class Constructors extends MiniPhaseTransform with IdentityDenotTransformer { th
    */
   override def checkPostCondition(tree: tpd.Tree)(implicit ctx: Context): Unit = {
     tree match {
-      case tree: ValDef if tree.symbol.exists && tree.symbol.owner.isClass && !tree.symbol.is(Lazy) =>
+      case tree: ValDef if tree.symbol.exists && tree.symbol.owner.isClass && !tree.symbol.is(Lazy) && !tree.symbol.hasAnnotation(defn.ScalaStaticAnnot) =>
         assert(tree.rhs.isEmpty, i"$tree: initializer should be moved to constructors")
       case tree: DefDef if !tree.symbol.is(LazyOrDeferred) =>
         assert(!tree.rhs.isEmpty, i"unimplemented: $tree")
@@ -181,7 +181,7 @@ class Constructors extends MiniPhaseTransform with IdentityDenotTransformer { th
     def splitStats(stats: List[Tree]): Unit = stats match {
       case stat :: stats1 =>
         stat match {
-          case stat @ ValDef(name, tpt, _) if !stat.symbol.is(Lazy) =>
+          case stat @ ValDef(name, tpt, _) if !stat.symbol.is(Lazy) && !stat.symbol.hasAnnotation(defn.ScalaStaticAnnot) =>
             val sym = stat.symbol
             if (isRetained(sym)) {
               if (!stat.rhs.isEmpty && !isWildcardArg(stat.rhs))
diff --git a/src/dotty/tools/dotc/transform/Getters.scala b/src/dotty/tools/dotc/transform/Getters.scala
index 75235d0f5..31171dfab 100644
--- a/src/dotty/tools/dotc/transform/Getters.scala
+++ b/src/dotty/tools/dotc/transform/Getters.scala
@@ -56,6 +56,7 @@ class Getters extends MiniPhaseTransform with SymTransformer { thisTransform =>
       d.is(NoGetterNeeded) ||
       d.initial.asInstanceOf[SymDenotation].is(PrivateLocal) && !d.owner.is(Trait) && !isDerivedValueClass(d.owner) && !d.is(Flags.Lazy) ||
       d.is(Module) && d.isStatic ||
+      d.hasAnnotation(defn.ScalaStaticAnnot) ||
       d.isSelfSym
     if (d.isTerm && (d.is(Lazy) || d.owner.isClass) && d.info.isValueType && !noGetterNeeded) {
       val maybeStable = if (d.isStable) Stable else EmptyFlags
diff --git a/src/dotty/tools/dotc/transform/LazyVals.scala b/src/dotty/tools/dotc/transform/LazyVals.scala
index e42c7bae9..504f9250b 100644
--- a/src/dotty/tools/dotc/transform/LazyVals.scala
+++ b/src/dotty/tools/dotc/transform/LazyVals.scala
@@ -26,7 +26,7 @@ import dotty.tools.dotc.core.SymDenotations.SymDenotation
 import dotty.tools.dotc.core.DenotTransformers.{SymTransformer, IdentityDenotTransformer, DenotTransformer}
 import Erasure.Boxing.adaptToType
 
-class LazyVals extends MiniPhaseTransform with IdentityDenotTransformer with NeedsCompanions {
+class LazyVals extends MiniPhaseTransform with IdentityDenotTransformer {
   import LazyVals._
 
   import tpd._
@@ -49,11 +49,6 @@ class LazyVals extends MiniPhaseTransform with IdentityDenotTransformer with Nee
     * before this phase starts processing same tree */
   override def runsAfter = Set(classOf[Mixin])
 
-  def isCompanionNeeded(cls: ClassSymbol)(implicit ctx: Context): Boolean = {
-    def hasLazyVal(cls: ClassSymbol) = cls.info.decls.exists(_.is(Flags.Lazy))
-    hasLazyVal(cls) || cls.mixins.exists(hasLazyVal)
-  }
-
   override def transformDefDef(tree: tpd.DefDef)(implicit ctx: Context, info: TransformerInfo): tpd.Tree =
    transformLazyVal(tree)
 
@@ -341,26 +336,28 @@ class LazyVals extends MiniPhaseTransform with IdentityDenotTransformer with Nee
         val tpe = x.tpe.widen.resultType.widen
         val claz = x.symbol.owner.asClass
         val thizClass = Literal(Constant(claz.info))
-        val companion = claz.companionModule
         val helperModule = ctx.requiredModule("dotty.runtime.LazyVals")
         val getOffset = Select(ref(helperModule), lazyNme.RLazyVals.getOffset)
         var offsetSymbol: TermSymbol = null
         var flag: Tree = EmptyTree
         var ord = 0
 
+        def offsetName(id: Int) = (StdNames.nme.LAZY_FIELD_OFFSET + (if(x.symbol.owner.is(Flags.Module)) "_m_" else "") + id.toString).toTermName
+
         // compute or create appropriate offsetSymol, bitmap and bits used by current ValDef
-        appendOffsetDefs.get(companion.moduleClass) match {
+        appendOffsetDefs.get(claz) match {
           case Some(info) =>
             val flagsPerLong = (64 / dotty.runtime.LazyVals.BITS_PER_LAZY_VAL).toInt
             info.ord += 1
             ord = info.ord % flagsPerLong
             val id = info.ord / flagsPerLong
+            val offsetById = offsetName(id)
             if (ord != 0) { // there are unused bits in already existing flag
-              offsetSymbol = companion.moduleClass.info.decl((StdNames.nme.LAZY_FIELD_OFFSET + id.toString).toTermName)
+              offsetSymbol = claz.info.decl(offsetById)
                 .suchThat(sym => (sym is Flags.Synthetic) && sym.isTerm)
                  .symbol.asTerm
             } else { // need to create a new flag
-              offsetSymbol = ctx.newSymbol(companion.moduleClass, (StdNames.nme.LAZY_FIELD_OFFSET + id.toString).toTermName, Flags.Synthetic, defn.LongType).enteredAfter(this)
+              offsetSymbol = ctx.newSymbol(claz, offsetById, Flags.Synthetic, defn.LongType).enteredAfter(this)
               offsetSymbol.addAnnotation(Annotation(defn.ScalaStaticAnnot))
               val flagName = (StdNames.nme.BITMAP_PREFIX + id.toString).toTermName
               val flagSymbol = ctx.newSymbol(claz, flagName, containerFlags, defn.LongType).enteredAfter(this)
@@ -370,13 +367,13 @@ class LazyVals extends MiniPhaseTransform with IdentityDenotTransformer with Nee
             }
 
           case None =>
-            offsetSymbol = ctx.newSymbol(companion.moduleClass, (StdNames.nme.LAZY_FIELD_OFFSET + "0").toTermName, Flags.Synthetic, defn.LongType).enteredAfter(this)
+            offsetSymbol = ctx.newSymbol(claz, offsetName(0), Flags.Synthetic, defn.LongType).enteredAfter(this)
             offsetSymbol.addAnnotation(Annotation(defn.ScalaStaticAnnot))
             val flagName = (StdNames.nme.BITMAP_PREFIX + "0").toTermName
             val flagSymbol = ctx.newSymbol(claz, flagName, containerFlags, defn.LongType).enteredAfter(this)
             flag = ValDef(flagSymbol, Literal(Constants.Constant(0L)))
             val offsetTree = ValDef(offsetSymbol, getOffset.appliedTo(thizClass, Literal(Constant(flagName.toString))))
-            appendOffsetDefs += (companion.moduleClass -> new OffsetInfo(List(offsetTree), ord))
+            appendOffsetDefs += (claz -> new OffsetInfo(List(offsetTree), ord))
         }
 
         val containerName = ctx.freshName(x.name.asTermName.lazyLocalName).toTermName
diff --git a/src/dotty/tools/dotc/transform/MoveStatics.scala b/src/dotty/tools/dotc/transform/MoveStatics.scala
new file mode 100644
index 000000000..5c2cd3145
--- /dev/null
+++ b/src/dotty/tools/dotc/transform/MoveStatics.scala
@@ -0,0 +1,77 @@
+package dotty.tools.dotc.transform
+
+import dotty.tools.dotc.ast.{Trees, tpd}
+import dotty.tools.dotc.core.Annotations.Annotation
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.core.DenotTransformers.{InfoTransformer, SymTransformer}
+import dotty.tools.dotc.core.SymDenotations.SymDenotation
+import dotty.tools.dotc.core.Decorators._
+import dotty.tools.dotc.core.NameOps._
+import dotty.tools.dotc.core.{Flags, Names}
+import dotty.tools.dotc.core.Names.Name
+import dotty.tools.dotc.core.Symbols._
+import dotty.tools.dotc.core.Types.MethodType
+import dotty.tools.dotc.transform.TreeTransforms.{MiniPhaseTransform, TransformerInfo}
+
+/** Move static methods from companion to the class itself */
+class MoveStatics extends MiniPhaseTransform with SymTransformer { thisTransformer =>
+
+  import tpd._
+  override def phaseName = "moveStatic"
+
+
+  def transformSym(sym: SymDenotation)(implicit ctx: Context): SymDenotation = {
+    if (sym.hasAnnotation(defn.ScalaStaticAnnot) && sym.owner.is(Flags.Module) && sym.owner.companionClass.exists) {
+      sym.owner.asClass.delete(sym.symbol)
+      sym.owner.companionClass.asClass.enter(sym.symbol)
+      val flags = if (sym.is(Flags.Method)) sym.flags else sym.flags | Flags.Mutable
+      sym.copySymDenotation(owner = sym.owner.companionClass, initFlags = flags)
+    }
+    else sym
+  }
+
+  override def transformStats(trees: List[Tree])(implicit ctx: Context, info: TransformerInfo): List[Tree] = {
+    if (ctx.owner.is(Flags.Package)) {
+      val (classes, others) = trees.partition(x => x.isInstanceOf[TypeDef] && x.symbol.isClass)
+      val pairs = classes.groupBy(_.symbol.name.stripModuleClassSuffix).asInstanceOf[Map[Name, List[TypeDef]]]
+
+      def rebuild(orig: TypeDef, newBody: List[Tree]): Tree = {
+        if (orig eq null) return EmptyTree
+
+        val staticFields = newBody.filter(x => x.isInstanceOf[ValDef] && x.symbol.hasAnnotation(defn.ScalaStaticAnnot)).asInstanceOf[List[ValDef]]
+        val newBodyWithStaticConstr =
+          if (staticFields.nonEmpty) {
+            /* do NOT put Flags.JavaStatic here. It breaks .enclosingClass */
+            val staticCostructor = ctx.newSymbol(orig.symbol, Names.STATIC_CONSTRUCTOR, Flags.Synthetic | Flags.Method | Flags.Private, MethodType(Nil, defn.UnitType))
+            staticCostructor.addAnnotation(Annotation(defn.ScalaStaticAnnot))
+            staticCostructor.entered
+
+            val staticAssigns = staticFields.map(x => Assign(ref(x.symbol), x.rhs.changeOwner(x.symbol, staticCostructor)))
+            tpd.DefDef(staticCostructor, Block(staticAssigns, tpd.unitLiteral)) :: newBody
+          } else newBody
+
+        val oldTemplate = orig.rhs.asInstanceOf[Template]
+        cpy.TypeDef(orig)(rhs = cpy.Template(orig.rhs)(oldTemplate.constr, oldTemplate.parents, oldTemplate.self, newBodyWithStaticConstr))
+      }
+
+      def move(module: TypeDef, companion: TypeDef): List[Tree] = {
+        if (!module.symbol.is(Flags.Module)) move(companion, module)
+        else {
+          val allMembers =
+            (if(companion ne null) {companion.rhs.asInstanceOf[Template].body} else Nil) ++
+            module.rhs.asInstanceOf[Template].body
+          val (newModuleBody, newCompanionBody) = allMembers.partition(x => {assert(x.symbol.exists); x.symbol.owner == module.symbol})
+          Trees.flatten(rebuild(companion, newCompanionBody) :: rebuild(module, newModuleBody) :: Nil)
+        }
+      }
+      val newPairs =
+        for ((name, classes) <- pairs)
+          yield
+            if (classes.tail.isEmpty)
+              if (classes.head.symbol.is(Flags.Module)) move(classes.head, null)
+              else List(rebuild(classes.head, classes.head.rhs.asInstanceOf[Template].body))
+            else move(classes.head, classes.tail.head)
+      Trees.flatten(newPairs.toList.flatten ++ others)
+    } else trees
+  }
+}
diff --git a/src/dotty/tools/dotc/transform/TreeChecker.scala b/src/dotty/tools/dotc/transform/TreeChecker.scala
index 0dce0fd36..ce160d7b0 100644
--- a/src/dotty/tools/dotc/transform/TreeChecker.scala
+++ b/src/dotty/tools/dotc/transform/TreeChecker.scala
@@ -26,6 +26,9 @@ import collection.mutable
 import ProtoTypes._
 import config.Printers
 import java.lang.AssertionError
+
+import dotty.tools.dotc.core.Names
+
 import scala.util.control.NonFatal
 
 /** Run by -Ycheck option after a given phase, this class retypes all syntax trees
@@ -382,7 +385,7 @@ class TreeChecker extends Phase with SymTransformer {
     override def typedDefDef(ddef: untpd.DefDef, sym: Symbol)(implicit ctx: Context) =
       withDefinedSyms(ddef.tparams) {
         withDefinedSymss(ddef.vparamss) {
-          if (!sym.isClassConstructor) assert(isValidJVMMethodName(sym.name), s"${sym.fullName} name is invalid on jvm")
+          if (!sym.isClassConstructor && !(sym.name eq Names.STATIC_CONSTRUCTOR)) assert(isValidJVMMethodName(sym.name), s"${sym.fullName} name is invalid on jvm")
           val tpdTree = super.typedDefDef(ddef, sym)
           assert(isMethodType(sym.info), i"wrong type, expect a method type for ${sym.fullName}, but found: ${sym.info}")
           tpdTree
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 07710d3b1..ae8900c43 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -485,7 +485,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         def canAssign(sym: Symbol) = // allow assignments from the primary constructor to class fields
           sym.is(Mutable, butNot = Accessor) ||
           ctx.owner.isPrimaryConstructor && !sym.is(Method) && sym.owner == ctx.owner.owner ||
-          ctx.owner.name.isTraitSetterName
+          ctx.owner.name.isTraitSetterName || ctx.owner.isStaticConstructor
         lhsCore.tpe match {
           case ref: TermRef if canAssign(ref.symbol) =>
             assignType(cpy.Assign(tree)(lhs1, typed(tree.rhs, ref.info)))
diff --git a/tests/neg/static-implements.scala b/tests/neg/static-implements.scala
new file mode 100644
index 000000000..8e8a8800c
--- /dev/null
+++ b/tests/neg/static-implements.scala
@@ -0,0 +1,11 @@
+import annotation.static
+
+abstract class A { def x: Int }
+
+class T
+object T extends A {
+  @static override val x = 10 // error: static methods cannot implement stuff
+  def main(args: Array[String]): Unit = {
+    println((this: A).x)
+  }
+}
diff --git a/tests/neg/static-no-companion.scala b/tests/neg/static-no-companion.scala
new file mode 100644
index 000000000..982dddf88
--- /dev/null
+++ b/tests/neg/static-no-companion.scala
@@ -0,0 +1,4 @@
+import annotation.static
+object T {
+  @static val foo = 10 // error: needs companion class
+}
diff --git a/tests/run/Lazies1.scala b/tests/run/Lazies1.scala
new file mode 100644
index 000000000..34fecaf80
--- /dev/null
+++ b/tests/run/Lazies1.scala
@@ -0,0 +1,6 @@
+object T{ @volatile lazy val s = null}
+object Test{
+  def main(args: Array[String]): Unit = {
+    T.s
+  }
+}
diff --git a/tests/run/Lazies2.scala b/tests/run/Lazies2.scala
new file mode 100644
index 000000000..6b9aa8a39
--- /dev/null
+++ b/tests/run/Lazies2.scala
@@ -0,0 +1,8 @@
+class T{ @volatile lazy val s = null}
+object T{ @volatile lazy val s = null}
+object Test{
+  def main(args: Array[String]): Unit = {
+    T.s
+    (new T).s
+  }
+}