Merge pull request #2215 from paulp/issue/7228

SI-7228, bug in subtyping.

10 files changed, 128 insertions, 49 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 2331f82a58..5b11adf127 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -268,7 +268,7 @@ trait Implicits {
    */
   object Function1 {
     val Sym = FunctionClass(1)
-    def unapply(tp: Type) = tp match {
+    def unapply(tp: Type) = tp baseType Sym match {
       case TypeRef(_, Sym, arg1 :: arg2 :: _) => Some((arg1, arg2))
       case _                                  => None
     }
@@ -431,10 +431,8 @@ trait Implicits {
       val start = if (Statistics.canEnable) Statistics.startTimer(matchesPtNanos) else null
       val result = normSubType(tp, pt) || isView && {
         pt match {
-          case TypeRef(_, Function1.Sym, arg1 :: arg2 :: Nil) =>
-            matchesPtView(tp, arg1, arg2, undet)
-          case _ =>
-            false
+          case Function1(arg1, arg2) => matchesPtView(tp, arg1, arg2, undet)
+          case _                     => false
         }
       }
       if (Statistics.canEnable) Statistics.stopTimer(matchesPtNanos, start)
@@ -575,21 +573,21 @@ trait Implicits {
       )
 
       def fail(reason: String): SearchResult = failure(itree, reason)
+      def fallback = typed1(itree, EXPRmode, wildPt)
       try {
-        val itree1 =
-          if (isView) {
-            val arg1 :: arg2 :: _ = pt.typeArgs
+        val itree1 = if (!isView) fallback else pt match {
+          case Function1(arg1, arg2) =>
             typed1(
               atPos(itree.pos)(Apply(itree, List(Ident("<argument>") setType approximate(arg1)))),
               EXPRmode,
               approximate(arg2)
             )
-          }
-          else
-            typed1(itree, EXPRmode, wildPt)
-
-        if (context.hasErrors)
+          case _ => fallback
+        }
+        if (context.hasErrors) {
+          log("implicit adapt failed: " + context.errBuffer.head.errMsg)
           return fail(context.errBuffer.head.errMsg)
+        }
 
         if (Statistics.canEnable) Statistics.incCounter(typedImplicits)
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index 007c7c6a83..d5da4967be 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -805,23 +805,19 @@ trait Namers extends MethodSynthesis {
         case _ =>
           false
       }
-
-      val tpe1 = dropIllegalStarTypes(tpe.deconst)
-      val tpe2 = tpe1.widen
-
-      // This infers Foo.type instead of "object Foo"
-      // See Infer#adjustTypeArgs for the polymorphic case.
-      if (tpe.typeSymbolDirect.isModuleClass) tpe1
-      else if (sym.isVariable || sym.isMethod && !sym.hasAccessorFlag)
-        if (tpe2 <:< pt) tpe2 else tpe1
-      else if (isHidden(tpe)) tpe2
-      // In an attempt to make pattern matches involving method local vals
-      // compilable into switches, for a time I had a more generous condition:
-      //    `if (sym.isFinal || sym.isLocal) tpe else tpe1`
-      // This led to issues with expressions like classOf[List[_]] which apparently
-      // depend on being deconst-ed here, so this is again the original:
-      else if (!sym.isFinal) tpe1
-      else tpe
+      val shouldWiden = (
+           !tpe.typeSymbolDirect.isModuleClass // Infer Foo.type instead of "object Foo"
+        && (tpe.widen <:< pt)                  // Don't widen our way out of conforming to pt
+        && (   sym.isVariable
+            || sym.isMethod && !sym.hasAccessorFlag
+            || isHidden(tpe)
+           )
+      )
+      dropIllegalStarTypes(
+        if (shouldWiden) tpe.widen
+        else if (sym.isFinal) tpe    // "final val" allowed to retain constant type
+        else tpe.deconst
+      )
     }
     /** Computes the type of the body in a ValDef or DefDef, and
      *  assigns the type to the tpt's node.  Returns the type.
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 92f53f4956..ba34ae4871 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -1124,16 +1124,19 @@ trait Typers extends Adaptations with Tags {
               else {
                 if (mode.inExprModeButNot(FUNmode)) {
                   pt.dealias match {
-                    case TypeRef(_, sym, _) =>
+                    // The <: Any requirement inhibits attempts to adapt continuation types
+                    // to non-continuation types.
+                    case TypeRef(_, sym, _) if tree.tpe <:< AnyClass.tpe =>
                       // note: was if (pt.typeSymbol == UnitClass) but this leads to a potentially
                       // infinite expansion if pt is constant type ()
-                      if (sym == UnitClass && tree.tpe <:< AnyClass.tpe) { // (12)
+                      if (sym == UnitClass) { // (12)
                         if (settings.warnValueDiscard.value)
                           context.unit.warning(tree.pos, "discarded non-Unit value")
                         return typedPos(tree.pos, mode, pt) {
                           Block(List(tree), Literal(Constant()))
                         }
-                      } else if (isNumericValueClass(sym) && isNumericSubType(tree.tpe, pt)) {
+                      }
+                      else if (isNumericValueClass(sym) && isNumericSubType(tree.tpe, pt)) {
                         if (settings.warnNumericWiden.value)
                           context.unit.warning(tree.pos, "implicit numeric widening")
                         return typedPos(tree.pos, mode, pt) {
diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index fe5a5c81e2..bfba81c654 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -1131,7 +1131,7 @@ trait Definitions extends api.StandardDefinitions {
     /** Is type's symbol a numeric value class? */
     def isNumericValueType(tp: Type): Boolean = tp match {
       case TypeRef(_, sym, _) => isNumericValueClass(sym)
-      case _ => false
+      case _                  => false
     }
 
     // todo: reconcile with javaSignature!!!
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index e1433d1893..ce514e9a89 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -1217,7 +1217,7 @@ trait Types
     protected def rewrap(newtp: Type): Type = NotNullType(newtp)
     override def isNotNull: Boolean = true
     override def notNull = this
-    override def deconst: Type = underlying //todo: needed?
+    override def deconst: Type = underlying.deconst //todo: needed?
     override def safeToString: String = underlying.toString + " with NotNull"
     override def kind = "NotNullType"
   }
@@ -1989,7 +1989,7 @@ trait Types
     assert(underlying.typeSymbol != UnitClass)
     override def isTrivial: Boolean = true
     override def isNotNull = value.value != null
-    override def deconst: Type = underlying
+    override def deconst: Type = underlying.deconst
     override def safeToString: String =
       underlying.toString + "(" + value.escapedStringValue + ")"
     override def kind = "ConstantType"
diff --git a/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala b/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
index 82321f61c2..a03ab1610e 100644
--- a/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
+++ b/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
@@ -5,6 +5,7 @@ package tpe
 import scala.collection.{ mutable }
 import Flags._
 import util.Statistics
+import scala.annotation.tailrec
 
 trait TypeComparers {
   self: SymbolTable =>
@@ -583,9 +584,9 @@ trait TypeComparers {
 
 
   def isWeakSubType(tp1: Type, tp2: Type) =
-    tp1.deconst.normalize match {
+    tp1.dealiasWiden match {
       case TypeRef(_, sym1, _) if isNumericValueClass(sym1) =>
-        tp2.deconst.normalize match {
+        tp2.deconst.dealias match {
           case TypeRef(_, sym2, _) if isNumericValueClass(sym2) =>
             isNumericSubClass(sym1, sym2)
           case tv2 @ TypeVar(_, _) =>
@@ -594,7 +595,7 @@ trait TypeComparers {
             isSubType(tp1, tp2)
         }
       case tv1 @ TypeVar(_, _) =>
-        tp2.deconst.normalize match {
+        tp2.deconst.dealias match {
           case TypeRef(_, sym2, _) if isNumericValueClass(sym2) =>
             tv1.registerBound(tp2, isLowerBound = false, isNumericBound = true)
           case _ =>
@@ -604,14 +605,18 @@ trait TypeComparers {
         isSubType(tp1, tp2)
     }
 
-  /** The isNumericValueType tests appear redundant, but without them
-    *  test/continuations-neg/function3.scala goes into an infinite loop.
-    *  (Even if the calls are to typeSymbolDirect.)
-    */
-  def isNumericSubType(tp1: Type, tp2: Type): Boolean = (
-    isNumericValueType(tp1)
-      && isNumericValueType(tp2)
-      && isNumericSubClass(tp1.typeSymbol, tp2.typeSymbol)
-    )
-
+  def isNumericSubType(tp1: Type, tp2: Type) = (
+    isNumericSubClass(primitiveBaseClass(tp1.dealiasWiden), primitiveBaseClass(tp2.dealias))
+   )
+
+  /** If the given type has a primitive class among its base classes,
+   *  the symbol of that class. Otherwise, NoSymbol.
+   */
+  private def primitiveBaseClass(tp: Type): Symbol = {
+    @tailrec def loop(bases: List[Symbol]): Symbol = bases match {
+      case Nil     => NoSymbol
+      case x :: xs => if (isPrimitiveValueClass(x)) x else loop(xs)
+    }
+    loop(tp.baseClasses)
+  }
 }
diff --git a/test/files/pos/switch-small.flags b/test/files/pos/switch-small.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/pos/switch-small.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/pos/t7228.scala b/test/files/pos/t7228.scala
new file mode 100644
index 0000000000..5d936f6529
--- /dev/null
+++ b/test/files/pos/t7228.scala
@@ -0,0 +1,75 @@
+object AdaptWithWeaklyConformantType {
+  implicit class D(d: Double) { def double = d*2 }
+
+  val x1: Int = 1
+  var x2: Int = 2
+  val x3 = 3
+  var x4 = 4
+  final val x5 = 5
+  final var x6 = 6
+
+  def f1 = x1.double
+  def f2 = x2.double
+  def f3 = x3.double
+  def f4 = x4.double
+  def f5 = x5.double
+  def f6 = x6.double
+}
+
+object AdaptAliasWithWeaklyConformantType {
+  implicit class D(d: Double) { def double = d*2 }
+  type T = Int
+
+  val x1: T = 1
+  var x2: T = 2
+  val x3 = (3: T)
+  var x4 = (4: T)
+  final val x5 = (5: T)
+  final var x6 = (6: T)
+
+  def f1 = x1.double
+  def f2 = x2.double
+  def f3 = x3.double
+  def f4 = x4.double
+  def f5 = x5.double
+  def f6 = x6.double
+}
+
+object AdaptToAliasWithWeaklyConformantType {
+  type U = Double
+  implicit class D(d: U) { def double = d*2 }
+
+  val x1: Int = 1
+  var x2: Int = 2
+  val x3 = (3: Int)
+  var x4 = (4: Int)
+  final val x5 = (5: Int)
+  final var x6 = (6: Int)
+
+  def f1 = x1.double
+  def f2 = x2.double
+  def f3 = x3.double
+  def f4 = x4.double
+  def f5 = x5.double
+  def f6 = x6.double
+}
+
+object AdaptAliasToAliasWithWeaklyConformantType {
+  type U = Double
+  type T = Int
+  implicit class D(d: U) { def double = d*2 }
+
+  val x1: T = 1
+  var x2: T = 2
+  val x3 = (3: T)
+  var x4 = (4: T)
+  final val x5 = (5: T)
+  final var x6 = (6: T)
+
+  def f1 = x1.double
+  def f2 = x2.double
+  def f3 = x3.double
+  def f4 = x4.double
+  def f5 = x5.double
+  def f6 = x6.double
+}
diff --git a/test/pending/pos/no-widen-locals.flags b/test/pending/pos/no-widen-locals.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/pending/pos/no-widen-locals.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/pos/no-widen-locals.scala b/test/pending/pos/no-widen-locals.scala
index 013e63f0a2..013e63f0a2 100644
--- a/test/files/pos/no-widen-locals.scala
+++ b/test/pending/pos/no-widen-locals.scala