Fix #3634: Lazily evaluate static module accessors

We did not use lazy evaluation for static objects, because these are usually evauated
lazily by the backend. But that does not hold if the static module is an (accessor) def
instead of a val.

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) ||
+        (sym.isStatic && sym.is(Flags.Module, butNot = Flags.Method)))
+      tree
     else {
       val isField = sym.owner.isClass
       if (isField) {

tests/run/i3634.scala

@@ -0,0 +1,11 @@
+trait T {
+  case object Foo
+}
+
+object Bar extends T
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    assert(Bar.Foo == Bar.Foo) // false
+  }
+}