Showcase bug

Reproduce with:
sbt run -Ycheck:elimErasedValueType tests/pos/vcblock.scala
sbt run -Ycheck:elimErasedValueType tests/pos/vcif.scala

Author: smarter

src/dotty/tools/dotc/Compiler.scala

@@ -60,8 +60,8 @@ class Compiler {
            new ElimByName,
            new ResolveSuper),
       List(new Erasure),
-      List(new ElimErasedValueType,
-           new ValueClassesPeepholeOptimize,
+      List(new ElimErasedValueType),
+      List(//new ValueClassesPeepholeOptimize,
            new Mixin,
            new Memoize,
            new CapturedVars,

src/dotty/tools/dotc/transform/ElimErasedValueType.scala

@@ -89,10 +89,14 @@ class ElimErasedValueType extends MiniPhaseTransform with DenotTransformer {
     transformTypeOfTree(tree)
   override def transformSelect(tree: Select)(implicit ctx: Context, info: TransformerInfo): Tree =
     transformTypeOfTree(tree)
+
+  // Disabled to showcase the bug.
+  /*
   override def transformBlock(tree: Block)(implicit ctx: Context, info: TransformerInfo): Tree =
     transformTypeOfTree(tree)
   override def transformIf(tree: If)(implicit ctx: Context, info: TransformerInfo): Tree =
     transformTypeOfTree(tree)
+  */
   override def transformSeqLiteral(tree: SeqLiteral)(implicit ctx: Context, info: TransformerInfo): Tree =
     transformTypeOfTree(tree)
   override def transformTypeTree(tree: TypeTree)(implicit ctx: Context, info: TransformerInfo): Tree =

test/dotc/tests.scala

@@ -15,7 +15,7 @@ class tests extends CompilerTest {
 
   implicit val defaultOptions = noCheckOptions ++ List(
       "-Yno-deep-subtypes",
-      "-Ycheck:tailrec,resolveSuper,mixin,restoreScopes",
+      "-Ycheck:tailrec,resolveSuper,elimErasedValueType,mixin,restoreScopes",
       "-d", "./out/"
   )
 

tests/pos/vcblock.scala

@@ -0,0 +1,6 @@
+class Position(val foo: Int) extends AnyVal {
+  def thing(): Position = {
+    val y = new Position(1)
+    y
+  }
+}

tests/pos/vcif.scala

@@ -0,0 +1,4 @@
+class Position(val foo: Int) extends AnyVal {
+  def orElse(that: Position) =
+    if (this != null) this else that
+}