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

1 files changed, 48 insertions, 0 deletions

diff --git a/test/pending/pos/t5459.scala b/test/pending/pos/t5459.scala
new file mode 100644
index 0000000000..971e6f896d
--- /dev/null
+++ b/test/pending/pos/t5459.scala
@@ -0,0 +1,48 @@
+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
+}