Merge pull request #3719 from dotty-staging/fix-#3634

Fix #3624: Lazily evaluate static module accessors

Author: odersky

compiler/src/dotty/tools/dotc/transform/LazyVals.scala

@@ -36,7 +36,7 @@ class LazyVals extends MiniPhase with IdentityDenotTransformer {
   class OffsetInfo(var defs: List[Tree], var ord:Int)
   val appendOffsetDefs = mutable.Map.empty[Symbol, OffsetInfo]
 
-  override def phaseName: String = "LazyVals"
+  override def phaseName: String = "lazyVals"
 
   /** List of names of phases that should have finished processing of tree
     * before this phase starts processing same tree */
@@ -61,7 +61,10 @@ class LazyVals extends MiniPhase with IdentityDenotTransformer {
 
   def transformLazyVal(tree: ValOrDefDef)(implicit ctx: Context): Tree = {
     val sym = tree.symbol
-    if (!(sym is Flags.Lazy) || sym.owner.is(Flags.Trait) || (sym.isStatic && sym.is(Flags.Module))) tree
+    if (!(sym is Flags.Lazy) ||
+        sym.owner.is(Flags.Trait) || // val is accessor, lazy field will be implemented in subclass
+        (sym.isStatic && sym.is(Flags.Module, butNot = Flags.Method))) // static module vals are implemented in the JVM by lazy loading
+      tree
     else {
       val isField = sym.owner.isClass
       if (isField) {

tests/pending/run/implicits-numeric.scala

@@ -0,0 +1,7 @@
+object Test extends App {
+
+  implicit def _1: Long = 1L
+  implicit def _2: Int = 0
+
+  println(implicitly[AnyVal])
+}

tests/run/i3624.scala

@@ -0,0 +1,13 @@
+trait T {
+  case object Foo
+}
+
+object Bar extends T
+object Baz extends T
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    assert(Bar.Foo eq Bar.Foo)
+    assert(Bar.Foo ne Baz.Foo)
+  }
+}