Merge pull request #1758 from hubertp/2.10.x-issue/strip-tvars

When we strip tvars we should also recursively strip their instantiation...

Author: adriaanm

src/reflect/scala/reflect/internal/Types.scala

@@ -6605,11 +6605,11 @@ trait Types extends api.Types { self: SymbolTable =>
       case ExistentialType(qs, _) => qs
       case t => List()
     }
-    def stripType(tp: Type) = tp match {
+    def stripType(tp: Type): Type = tp match {
       case ExistentialType(_, res) =>
         res
       case tv@TypeVar(_, constr) =>
-        if (tv.instValid) constr.inst
+        if (tv.instValid) stripType(constr.inst)
         else if (tv.untouchable) tv
         else abort("trying to do lub/glb of typevar "+tp)
       case t => t

test/files/pos/strip-tvars-for-lubbasetypes.scala

@@ -0,0 +1,25 @@
+object Test {
+
+  implicit final class EqualOps[T](val x: T) extends AnyVal {
+    def ===[T1, Ph >: T <: T1, Ph2 >: Ph <: T1](other: T1): Boolean = x == other
+    def !!![T1, Ph2 >: Ph <: T1, Ph >: T <: T1](other: T1): Boolean = x == other
+  }
+
+  class A
+  class B extends A
+  class C extends A
+
+  val a = new A
+  val b = new B
+  val c = new C
+
+  val x1 = a === b
+  val x2 = b === a
+  val x3 = b === c // error, infers Object{} for T1
+  val x4 = b.===[A, B, B](c)
+
+  val x5 = b !!! c // always compiled due to the order of Ph2 and Ph
+
+
+
+}