Fixes to erasure

Makes erasure pass the test suite.

Erasure is not yet turned turned on by default, because TestNonCyclic fails
with a stale symbol error. The problem is that This types are coupled to Symbols
and therefore don't reload. This is a problem is This types refer to static symbols
that get recompiled. We either have to drop using This types for static references,
or redefine thme so that can be reloaded.

7 files changed, 61 insertions, 64 deletions

diff --git a/src/dotty/tools/dotc/TypeErasure.scala b/src/dotty/tools/dotc/TypeErasure.scala
index b65f2889f..c8c54ed03 100644
--- a/src/dotty/tools/dotc/TypeErasure.scala
+++ b/src/dotty/tools/dotc/TypeErasure.scala
@@ -109,6 +109,28 @@ object TypeErasure {
     }
     loop(tp1.baseClasses, defn.ObjectClass).typeRef
   }
+
+  def erasedGlb(tp1: Type, tp2: Type, isJava: Boolean)(implicit ctx: Context): Type = tp1 match {
+    case defn.ArrayType(elem1) =>
+      tp2 match {
+        case defn.ArrayType(elem2) => defn.ArrayType(erasedGlb(elem1, elem2, isJava))
+        case _ => defn.ObjectType
+      }
+    case _ =>
+      tp2 match {
+        case defn.ArrayType(_) => defn.ObjectType
+        case _ =>
+          val tsym1 = tp1.typeSymbol
+          val tsym2 = tp2.typeSymbol
+          if (!tsym2.exists) tp1
+          else if (!tsym1.exists) tp2
+          else if (!isJava && tsym1.derivesFrom(tsym2)) tp1
+          else if (!isJava && tsym2.derivesFrom(tsym1)) tp2
+          else if (tp1.typeSymbol.isRealClass) tp1
+          else if (tp2.typeSymbol.isRealClass) tp2
+          else tp1
+      }
+  }
 }
 import TypeErasure._
 
@@ -127,15 +149,15 @@ class TypeErasure(isJava: Boolean, isSemi: Boolean, isConstructor: Boolean, wild
    *      - otherwise, if T <: Object, scala.Array+[|T|]
    *      - otherwise, if T is a type paramter coming from Java, scala.Array+[Object].
    *      - otherwise, Object
-   *   - For all other type proxies: The erasure of the underlying type.
-   *   - For a typeref scala.Any, scala.AnyVal, scala.Singleon or scala.NotNull: java.lang.Object.
-   *   - For a typeref scala.Unit, scala.runtime.BoxedUnit.
-   *   - For a typeref whose symbol is owned by Array: The typeref itself
-   *   - For a typeref P.C where C refers to a toplevel class, P.C.
-   *   - For a typeref P.C where C refers to a nested class, |P|.C.
+   *   - For a term ref p.x, the type <noprefix> # x.
+   *   - For a typeref scala.Any, scala.AnyVal, scala.Singleon or scala.NotNull: |java.lang.Object|
+   *   - For a typeref scala.Unit, |scala.runtime.BoxedUnit|.
+   *   - For a typeref whose symbol is owned by Array: The typeref itself, with prefix = <noprefix>
+   *   - For a typeref P.C where C refers to a class, <noprefix> # C.
    *   - For a typeref P.C where C refers to an alias type, the erasure of C's alias.
    *   - For a typeref P.C where C refers to an abstract type, the erasure of C's upper bound.
-   *   - For T1 & T2, the merge of |T1| and |T2| (see mergeAnd)
+   *   - For all other type proxies: The erasure of the underlying type.
+   *   - For T1 & T2, the erased glb of |T1| and |T2| (see erasedGlb)
    *   - For T1 | T2, the first base class in the linearization of T which is also a base class of T2
    *   - For => T, ()T
    *   - For a method type (Fs)scala.Unit, (|Fs|)scala.Unit.
@@ -164,14 +186,12 @@ class TypeErasure(isJava: Boolean, isSemi: Boolean, isConstructor: Boolean, wild
     case tp: TermRef =>
       assert(tp.symbol.exists, tp)
       TermRef(NoPrefix, tp.symbol.asTerm)
-    case _: ThisType =>
-      tp
     case ExprType(rt) =>
       MethodType(Nil, Nil, this(rt))
     case tp: TypeProxy =>
       this(tp.underlying)
     case AndType(tp1, tp2) =>
-      mergeAnd(this(tp1), this(tp2))
+      erasedGlb(this(tp1), this(tp2), isJava)
     case OrType(tp1, tp2) =>
       ctx.typeComparer.orType(this(tp1), this(tp2), erased = true)
     case tp: MethodType =>
@@ -196,7 +216,8 @@ class TypeErasure(isJava: Boolean, isSemi: Boolean, isConstructor: Boolean, wild
           if ((cls eq defn.ObjectClass) || cls.isPrimitiveValueClass) Nil
           else if (cls eq defn.ArrayClass) defn.ObjectClass.typeRef :: Nil
           else removeLaterObjects(classParents.mapConserve(eraseTypeRef))
-        tp.derivedClassInfo(this(pre), parents, decls, this(tp.selfType))
+        tp.derivedClassInfo(NoPrefix, parents, decls, this(tp.selfType))
+          // can't replace selftype by NoType because this would lose the sourceModule link
       }
     case NoType | NoPrefix | ErrorType =>
       tp
@@ -215,9 +236,8 @@ class TypeErasure(isJava: Boolean, isSemi: Boolean, isConstructor: Boolean, wild
     unsupported("eraseDerivedValueClass")
 
   private def eraseNormalClassRef(tref: TypeRef)(implicit ctx: Context): Type = {
-    val sym = tref.symbol
-    if (sym.owner is Package) normalizeClass(sym.asClass).typeRef
-    else tref.derivedSelect(this(tref.prefix))
+    val cls = tref.symbol.asClass
+    (if (cls.owner is Package) normalizeClass(cls) else cls).typeRef
   }
 
   private def eraseResult(tp: Type)(implicit ctx: Context): Type = tp match {
@@ -247,28 +267,6 @@ class TypeErasure(isJava: Boolean, isSemi: Boolean, isConstructor: Boolean, wild
     case nil => nil
   }
 
-  private def mergeAnd(tp1: Type, tp2: Type)(implicit ctx: Context): Type = tp1 match {
-    case defn.ArrayType(elem1) =>
-      tp2 match {
-        case defn.ArrayType(elem2) => defn.ArrayType(mergeAnd(elem1, elem2))
-        case _ => defn.ObjectType
-      }
-    case _ =>
-      tp2 match {
-        case defn.ArrayType(_) => defn.ObjectType
-        case _ =>
-          val tsym1 = tp1.typeSymbol
-          val tsym2 = tp2.typeSymbol
-          if (!tsym2.exists) tp1
-          else if (!tsym1.exists) tp2
-          else if (!isJava && tsym1.derivesFrom(tsym2)) tp1
-          else if (!isJava && tsym2.derivesFrom(tsym1)) tp2
-          else if (tp1.typeSymbol.isRealClass) tp1
-          else if (tp2.typeSymbol.isRealClass) tp2
-          else tp1
-      }
-  }
-
   /** The name of the type as it is used in `Signature`s.
    *  Need to ensure correspondence with erasure!
    */
diff --git a/src/dotty/tools/dotc/core/Definitions.scala b/src/dotty/tools/dotc/core/Definitions.scala
index 9018d4015..304d9853c 100644
--- a/src/dotty/tools/dotc/core/Definitions.scala
+++ b/src/dotty/tools/dotc/core/Definitions.scala
@@ -377,9 +377,9 @@ class Definitions {
   }
 
   object ArrayType {
-    def apply(elem: Type) =
+    def apply(elem: Type)(implicit ctx: Context) =
       ArrayClass.typeRef.appliedTo(elem :: Nil)
-    def unapply(tp: Type) = tp.dealias match {
+    def unapply(tp: Type)(implicit ctx: Context) = tp.dealias match {
       case at: RefinedType if (at isRef ArrayClass) && at.argInfos.length == 1 => Some(at.argInfos.head)
       case _ => None
     }
diff --git a/src/dotty/tools/dotc/core/SymDenotations.scala b/src/dotty/tools/dotc/core/SymDenotations.scala
index 7ba6bbec6..63ce7f756 100644
--- a/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -922,7 +922,7 @@ object SymDenotations {
     /** The type parameters of this class */
     override final def typeParams(implicit ctx: Context): List[TypeSymbol] = {
       def computeTypeParams = {
-        if (ctx.phase.erasedTypes && (this ne defn.ArrayClass)) Nil
+        if (ctx.phase.erasedTypes && (symbol ne defn.ArrayClass)) Nil
         else if (this ne initial) initial.asSymDenotation.typeParams
         else decls.filter(sym =>
           (sym is TypeParam) && sym.owner == symbol).asInstanceOf[List[TypeSymbol]]
diff --git a/src/dotty/tools/dotc/core/TypeComparer.scala b/src/dotty/tools/dotc/core/TypeComparer.scala
index 4d818cc6f..29f6dda69 100644
--- a/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -11,7 +11,7 @@ import printing.Disambiguation.disambiguated
 import util.{Stats, DotClass, SimpleMap}
 import config.Config
 import config.Printers._
-import TypeErasure.erasedLub
+import TypeErasure.{erasedLub, erasedGlb}
 
 /** Provides methods to compare types.
  */
@@ -1066,12 +1066,13 @@ class TypeComparer(initctx: Context) extends DotClass {
    *  Such TypeBounds can also be arbitrarily instantiated. In both cases we need to
    *  make sure that such types do not actually arise in source programs.
    */
-  final def andType(tp1: Type, tp2: Type) = ctx.traceIndented(s"glb(${tp1.show}, ${tp2.show})", subtyping, show = true) {
+  final def andType(tp1: Type, tp2: Type, erased: Boolean = ctx.erasedTypes) = ctx.traceIndented(s"glb(${tp1.show}, ${tp2.show})", subtyping, show = true) {
     val t1 = distributeAnd(tp1, tp2)
     if (t1.exists) t1
     else {
       val t2 = distributeAnd(tp2, tp1)
       if (t2.exists) t2
+      else if (erased) erasedGlb(tp1, tp2, isJava = false)
       else {
         //if (isHKRef(tp1)) tp2
         //else if (isHKRef(tp2)) tp1
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index a8bfe61e0..e59c28ca2 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -21,7 +21,7 @@ import ast.tpd._
 import ast.TreeTypeMap
 import printing.Texts._
 import ast.untpd
-import transform.Erasure
+import dotty.tools.dotc.transform.Erasure
 import printing.Printer
 import Hashable._
 import Uniques._
@@ -2183,17 +2183,17 @@ object Types {
     def selfType(implicit ctx: Context): Type = {
       if (selfTypeCache == null) {
         def fullRef = fullyAppliedRef(cls.typeRef, cls.typeParams)
-        selfTypeCache =
-          if (ctx.erasedTypes) fullRef
-          else selfInfo match {
-            case NoType =>
-              fullRef
-            case tp: Type =>
-              if (cls is Module) tp else AndType(tp, fullRef)
-            case self: Symbol =>
-              assert(!(cls is Module))
-              AndType(self.info, fullRef)
-          }
+        def withFullRef(tp: Type): Type =
+          if (ctx.erasedTypes) fullRef else AndType(tp, fullRef)
+        selfTypeCache = selfInfo match {
+          case NoType =>
+            fullRef
+          case tp: Type =>
+            if (cls is Module) tp else withFullRef(tp)
+          case self: Symbol =>
+            assert(!(cls is Module))
+            withFullRef(self.info)
+        }
       }
       selfTypeCache
     }
@@ -2210,7 +2210,7 @@ object Types {
     }
 
     def rebase(tp: Type)(implicit ctx: Context): Type =
-      if ((prefix eq cls.owner.thisType) || !cls.owner.isClass) tp
+      if ((prefix eq cls.owner.thisType) || !cls.owner.isClass || ctx.erasedTypes) tp
       else tp.substThis(cls.owner.asClass, prefix)
 
     private var typeRefCache: Type = null
diff --git a/src/dotty/tools/dotc/transform/Erasure.scala b/src/dotty/tools/dotc/transform/Erasure.scala
index 53e253c69..1efc6b53c 100644
--- a/src/dotty/tools/dotc/transform/Erasure.scala
+++ b/src/dotty/tools/dotc/transform/Erasure.scala
@@ -175,12 +175,13 @@ object Erasure {
      *    e -> unbox(e, PT)  if `PT` is a primitive type and `e` is not of primitive type
      *    e -> cast(e, PT)   otherwise
      */
-    def adaptToType(tree: Tree, pt: Type)(implicit ctx: Context): Tree = {
-      def makeConformant(tpw: Type): Tree = tpw match {
-        case MethodType(Nil, _) =>
+    def adaptToType(tree: Tree, pt: Type)(implicit ctx: Context): Tree =
+      if (pt.isInstanceOf[FunProto]) tree
+      else tree.tpe.widen match {
+        case MethodType(Nil, _) if tree.isTerm =>
           adaptToType(tree.appliedToNone, pt)
-        case _ =>
-          if (pt.isInstanceOf[ProtoType])
+        case tpw =>
+          if (pt.isInstanceOf[ProtoType] || tree.tpe <:< pt)
             tree
           else if (tpw.isErasedValueType)
             adaptToType(box(tree), pt)
@@ -193,9 +194,6 @@ object Erasure {
           else
             cast(tree, pt)
       }
-      if ((pt.isInstanceOf[FunProto]) || tree.tpe <:< pt) tree
-      else makeConformant(tree.tpe.widen)
-    }
   }
 
   class Typer extends typer.ReTyper with NoChecking {
@@ -254,7 +252,7 @@ object Erasure {
         else if (qual.tpe.derivesFrom(sym.owner) || qual.isInstanceOf[Super])
           select(qual, sym)
         else if (sym.owner eq defn.ArrayClass)
-          selectArrayMember(qual, erasure(tree.qualifier.typeOpt.widen))
+          selectArrayMember(qual, erasure(tree.qualifier.typeOpt.widen.finalResultType))
         else
           recur(cast(qual, sym.owner.typeRef))
       }
diff --git a/test/dotc/tests.scala b/test/dotc/tests.scala
index 387bab97f..35f85c4d8 100644
--- a/test/dotc/tests.scala
+++ b/test/dotc/tests.scala
@@ -17,7 +17,7 @@ class tests extends CompilerTest {
     "-Ycheck:literalize"
   )
 
-  val twice = List("#runs", "2", "-YnoDoubleBindings"/*, "-Ystop-before:terminal"*/)
+  val twice = List("#runs", "2", "-YnoDoubleBindings", "-Ystop-before:terminal")
   val doErase = List("-Ystop-before:terminal")
 
   val posDir = "./tests/pos/"