Simplify: drop more stuff in dropNoEffects.

Author: DarkDimius

compiler/src/dotty/tools/dotc/transform/linker/Analysis.scala

@@ -7,6 +7,7 @@ import core.Contexts._
 import core.NameOps._
 import core.StdNames._
 import core.Symbols._
+import dotty.tools.dotc.core.Flags
 
 object Analysis {
   import tpd._
@@ -35,6 +36,8 @@ object Analysis {
     "scala.Some"
   )
 
+  private val moduleWhiteList = constructorWhiteList.map(x => x + "$")
+
   private val methodsWhiteList = List(
     "java.lang.Math.min",
     "java.lang.Math.max",
@@ -56,6 +59,8 @@ object Analysis {
         true
       case Apply(fun, args) if methodsWhiteList.contains(fun.symbol.fullName.toString) =>
         true
+      case Ident(_) if t.symbol.is(Flags.Module) && (t.symbol.is(Flags.Synthetic) || moduleWhiteList.contains(t.symbol.fullName.toString)) =>
+        true
       case _ =>
         false
       // analisys

compiler/src/dotty/tools/dotc/transform/linker/Simplify.scala

@@ -849,10 +849,10 @@ class Simplify extends MiniPhaseTransform with IdentityDenotTransformer {
           case _ => keepOnlySideEffects(expr).orElse(unitLiteral)
         }
         tpd.cpy.Block(bl)(stats2, expr2)
-      case t: Ident if !t.symbol.is(Method | Lazy) && !t.symbol.info.isInstanceOf[ExprType] =>
+      case t: Ident if !t.symbol.is(Method | Lazy) && !t.symbol.info.isInstanceOf[ExprType] || Analysis.effectsDontEscape(t) =>
         desugarIdent(t) match {
-          case Some(t) => t
-          case None => EmptyTree
+          case Some(t) if !(t.qualifier.symbol.is(Flags.JavaDefined) && t.qualifier.symbol.is(Flags.Package)) => t
+          case _ => EmptyTree
         }
       case app: Apply if app.fun.symbol.is(Label) && !app.tpe.finalResultType.derivesFrom(defn.UnitClass) =>
         // This is "the scary hack". It changes the return type to Unit, then