6 files changed, 44 insertions, 8 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index d1cf9b1904..3bea049c59 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -1015,7 +1015,7 @@ trait Implicits {
                 args foreach (getParts(_))
               }
             } else if (sym.isAliasType) {
-              getParts(tp.dealias)
+              getParts(tp.normalize) // SI-7180 Normalize needed to expand HK type refs
             } else if (sym.isAbstractType) {
               getParts(tp.bounds.hi)
             }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index cff3f4f0fa..4fb68fc2a9 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -222,8 +222,13 @@ trait Typers extends Modes with Adaptations with Tags {
         new SubstWildcardMap(tparams).apply(tp)
       case TypeRef(_, sym, _) if sym.isAliasType =>
         val tp0 = tp.dealias
-        val tp1 = dropExistential(tp0)
-        if (tp1 eq tp0) tp else tp1
+        if (tp eq tp0) {
+          debugwarn(s"dropExistential did not progress dealiasing $tp, see SI-7126")
+          tp
+        } else {
+          val tp1 = dropExistential(tp0)
+          if (tp1 eq tp0) tp else tp1
+        }
       case _ => tp
     }
 
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index fb493fabd8..7299b439f8 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -3183,12 +3183,19 @@ trait Types extends api.Types { self: SymbolTable =>
        *    ?TC[?T] <: Any
        *  }}}
        */
-      def unifySimple = (
-        (params.isEmpty || tp.typeSymbol == NothingClass || tp.typeSymbol == AnyClass) && {
+      def unifySimple = {
+        val sym = tp.typeSymbol
+        if (sym == NothingClass || sym == AnyClass) { // kind-polymorphic
+          // SI-7126 if we register some type alias `T=Any`, we can later end
+          // with malformed types like `T[T]` during type inference in
+          // `handlePolymorphicCall`. No such problem if we register `Any`.
+          addBound(sym.tpe)
+          true
+        } else if (params.isEmpty) {
           addBound(tp)
           true
-        }
-      )
+        } else false
+      }
 
       /** Full case: involving a check of the form
        *  {{{
diff --git a/test/files/pos/t7126.scala b/test/files/pos/t7126.scala
new file mode 100644
index 0000000000..6720511e08
--- /dev/null
+++ b/test/files/pos/t7126.scala
@@ -0,0 +1,11 @@
+import language._
+
+object Test {
+  type T = Any
+  boom(???): Option[T] // SOE
+  def boom[CC[U]](t : CC[T]): Option[CC[T]] = None
+
+  // okay
+  foo(???): Option[Any]
+  def foo[CC[U]](t : CC[Any]): Option[CC[Any]] = None
+}
+\ No newline at end of file
diff --git a/test/files/pos/t7180.scala b/test/files/pos/t7180.scala
new file mode 100644
index 0000000000..15582f6df3
--- /dev/null
+++ b/test/files/pos/t7180.scala
@@ -0,0 +1,13 @@
+trait Higher[F[_]]
+
+trait Box[A]
+object Box {
+  implicit def HigherBox = new Higher[Box] {}
+}
+
+object Foo {
+  val box = implicitly[Higher[Box]] // compiles fine !!!
+
+  type Bar[A] = Box[A]
+  val bar = implicitly[Higher[Bar]] // <-- this doesn't compile in 2.10.1-RC1, but does in 2.10.0 !!!
+}
diff --git a/test/files/run/reflection-java-annotations/JavaSimpleEnumeration_1.java b/test/files/run/reflection-java-annotations/JavaSimpleEnumeration_1.java
index 39246141cc..5f4dcce8a7 100644
--- a/test/files/run/reflection-java-annotations/JavaSimpleEnumeration_1.java
+++ b/test/files/run/reflection-java-annotations/JavaSimpleEnumeration_1.java
@@ -1,4 +1,4 @@
-enum JavaSimpleEnumeration_1 {
+public enum JavaSimpleEnumeration_1 {
   FOO,
   BAR
 }
 \ No newline at end of file