Recurse into instantiations when stripping type vars.

This led to the inference of weird types as list
of lub base types was empty.
This change fixes case x3 in the test case.

2 files changed, 27 insertions, 2 deletions

diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index d82692000d..119a57d268 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/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
diff --git a/test/files/pos/strip-tvars-for-lubbasetypes.scala b/test/files/pos/strip-tvars-for-lubbasetypes.scala
new file mode 100644
index 0000000000..2be8625bae
--- /dev/null
+++ b/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
+
+
+
+}