Revert "SI-1786 incorporate defined bounds in inference"

Have to revert because the stricter bounds that it inferred break e.g., slick.
(Backstop for that added as pos/t1786-counter.scala, as minimized by Jason)
Worse, the fix was compilation order-dependent.

There's a less invasive fix (SI-6169) that could be generalized
in `sharpenQuantifierBounds` (used in `skolemizeExistential`),
but I'd rather not mess with existentials at this point.

This reverts commit e28c3edda4dd405ed382227d2a688b799bf33c72.

Conflicts:
	src/compiler/scala/tools/nsc/typechecker/Typers.scala
	test/files/pos/t1786.scala

3 files changed, 38 insertions, 67 deletions

diff --git a/test/files/pos/t1786-counter.scala b/test/files/pos/t1786-counter.scala
new file mode 100644
index 0000000000..c1ad2c204f
--- /dev/null
+++ b/test/files/pos/t1786-counter.scala
@@ -0,0 +1,38 @@
+trait ShapeLevel
+
+object Fail {
+  abstract class ProductNodeShape[Level <: ShapeLevel, C, M <: C, U <: C, P <: C] extends Shape[Level, M, U, P] {
+    def copy(shapes: Seq[Shape[_, _, _, _]]): Shape[Level, _, _, _]
+  }
+
+  abstract class Shape[Level <: ShapeLevel, -Mixed_, Unpacked_, Packed_]
+
+  final class TupleShape[Level <: ShapeLevel, M <: Product, U <: Product, P <: Product](val shapes: Shape[_, _, _, _]*) extends ProductNodeShape[Level, Product, M, U, P] {
+    def copy(shapes: Seq[Shape[_, _, _, _]]): Shape[Level, _, _, _] = ???
+  }
+
+  trait ShapeLevel
+}
+
+object Ok {
+  abstract class Shape[Level <: ShapeLevel, -Mixed_, Unpacked_, Packed_]
+
+  abstract class ProductNodeShape[Level <: ShapeLevel, C, M <: C, U <: C, P <: C] extends Shape[Level, M, U, P] {
+    def copy(shapes: Seq[Shape[_, _, _, _]]): Shape[Level, _, _, _]
+  }
+
+  final class TupleShape[Level <: ShapeLevel, M <: Product, U <: Product, P <: Product](val shapes: Shape[_, _, _, _]*) extends ProductNodeShape[Level, Product, M, U, P] {
+    def copy(shapes: Seq[Shape[_, _, _, _]]): Shape[Level, _, _, _] = ???
+  }
+}
+
+// This is why we reverted the fix for SI-1786 -- see SI-6169 for a potential alternative that could be extended to cover this.
+// both objects type check on 2.10.3, but only Ok was accepted by 2.11 after the original fix to SI-1786.
+// Fail results in:
+/*
+t1786-counter.scala:10: error: class TupleShape needs to be abstract, since method copy in class ProductNodeShape of type (shapes: Seq[Fail.Shape[_, _, _, _]])Fail.Shape[Level, _, _, _] is not defined
+(Note that Seq[Fail.Shape[_, _, _, _]] does not match Seq[Fail.Shape[_ <: Fail.ShapeLevel, _, _, _]]: their type parameters differ)
+  final class TupleShape[Level <: ShapeLevel, M <: Product, U <: Product, P <: Product](val shapes: Shape[_, _, _, _]*) extends ProductNodeShape[Level, Product, M, U, P] {
+              ^
+one error found
+*/
\ No newline at end of file
diff --git a/test/files/pos/t1786.scala b/test/files/pos/t1786.scala
deleted file mode 100644
index 32d6c06f6e..0000000000
--- a/test/files/pos/t1786.scala
+++ /dev/null
@@ -1,19 +0,0 @@
-class SomeClass(val intValue:Int)
-class MyClass[T <: SomeClass](val myValue:T)
-class Flooz[A >: Null <: SomeClass, T >: Null <: A](var value: T)
-
-class A {
-  def f1(i:MyClass[_])                       = i.myValue.intValue
-  def f2(i:MyClass[_ <: SomeClass])          = i.myValue.intValue
-  // def f3[T](i: MyClass[T])                   = i.myValue.intValue
-  def f4[T <: SomeClass](i: MyClass[T])      = i.myValue.intValue
-  // def f5[T >: Null](i: MyClass[T])           = i.myValue.intValue
-  // def f6[T >: Null <: String](i: MyClass[T]) = i.myValue.intValue + i.myValue.charAt(0)
-
-  // def g1[A, T](x: Flooz[A, T]) = { x.value = null ; x.value.intValue }
-  def g2(x: Flooz[_, _]) = { x.value = null ; x.value.intValue }
-
-  class MyClass2(x: MyClass[_]) { val p = x.myValue.intValue }
-  // class MyClass3[T <: String](x: MyClass[T]) { val p = x.myValue.intValue + x.myValue.length }
-  // class MyClass4[T >: Null](x: MyClass[T]) { val p = x.myValue.intValue }
-}
diff --git a/test/files/pos/t5459.scala b/test/files/pos/t5459.scala
deleted file mode 100644
index 971e6f896d..0000000000
--- a/test/files/pos/t5459.scala
+++ /dev/null
@@ -1,48 +0,0 @@
-trait A1
-trait A2
-trait A3
-trait L1 extends A1 with A2 with A3
-
-object Test {
-  trait T1[-A <: A1]
-  trait T2[-A >: L1]
-  trait T3[ A <: A1]
-  trait T4[ A >: L1]
-  trait T5[+A <: A1]
-  trait T6[+A >: L1]
-
-  def f1(x: T1[_]) = x
-  def f2(x: T2[_]) = x
-  def f3(x: T3[_]) = x
-  def f4(x: T4[_]) = x
-  def f5(x: T5[_]) = x
-  def f6(x: T6[_]) = x
-  // a.scala:22: error: type arguments [Any] do not conform to trait T5's type parameter bounds [+A <: A1]
-  //   def f5(x: T5[_]) = x
-  //       ^
-
-  def g1(x: T1[_ <: A1]) = x
-  def g2(x: T2[_ >: L1]) = x
-  def g3(x: T3[_ <: A1]) = x
-  def g4(x: T4[_ >: L1]) = x
-  def g5(x: T5[_ <: A1]) = x
-  def g6(x: T6[_ >: L1]) = x
-
-  def q1(x: T1[_ >: L1]) = x
-  def q2(x: T2[_ <: A1]) = x
-  def q3(x: T3[_ >: L1]) = x
-  def q4(x: T4[_ <: A1]) = x
-  def q5(x: T5[_ >: L1]) = x
-  def q6(x: T6[_ <: A1]) = x
-  // a.scala:41: error: type arguments [Any] do not conform to trait T5's type parameter bounds [+A <: A1]
-  //   def q5(x: T5[_ >: L1]) = x
-  //       ^
-  // two errors found
-
-  def h1(x: T1[_ >: L1 <: A1]) = x
-  def h2(x: T2[_ >: L1 <: A1]) = x
-  def h3(x: T3[_ >: L1 <: A1]) = x
-  def h4(x: T4[_ >: L1 <: A1]) = x
-  def h5(x: T5[_ >: L1 <: A1]) = x
-  def h6(x: T6[_ >: L1 <: A1]) = x
-}