Merge pull request #3160 from dotty-staging/enable-drop-no-effects

Re-enable DropNoEffects after erasure

Author: nicolasstucki

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

@@ -62,6 +62,7 @@ class Simplify extends MiniPhaseTransform with IdentityDenotTransformer {
     new Devalify                    ::
     new Jumpjump                    ::
     new DropGoodCasts               ::
+    new DropNoEffects(this)         ::
     new ConstantFold(this)          ::
     Nil