Merge pull request #1399 from paulp/210-unchecked

Much better unchecked warnings.

33 files changed, 528 insertions, 34 deletions

diff --git a/test/files/neg/patmat-type-check.check b/test/files/neg/patmat-type-check.check
index e045841ce1..721217c314 100644
--- a/test/files/neg/patmat-type-check.check
+++ b/test/files/neg/patmat-type-check.check
@@ -1,3 +1,12 @@
+patmat-type-check.scala:11: warning: fruitless type test: a value of type Test.Bop4[T] cannot also be a Seq[A]
+  def s3[T](x: Bop4[T]) = x match { case Seq('b', 'o', 'b') => true }
+                                            ^
+patmat-type-check.scala:15: warning: fruitless type test: a value of type Test.Bop5[_$1,T1,T2] cannot also be a Seq[A]
+  def s4[T1, T2](x: Bop5[_, T1, T2]) = x match { case Seq('b', 'o', 'b') => true }
+                                                         ^
+patmat-type-check.scala:19: warning: fruitless type test: a value of type Test.Bop3[T] cannot also be a Seq[A]
+  def f4[T](x: Bop3[T]) = x match { case Seq('b', 'o', 'b') => true }
+                                            ^
 patmat-type-check.scala:22: error: scrutinee is incompatible with pattern type;
  found   : Seq[A]
  required: String
@@ -18,4 +27,5 @@ patmat-type-check.scala:30: error: scrutinee is incompatible with pattern type;
  required: Test.Bop3[Char]
   def f4[T](x: Bop3[Char]) = x match { case Seq('b', 'o', 'b') => true } // fail
                                                ^
+three warnings found
 four errors found
diff --git a/test/files/neg/t1872.check b/test/files/neg/t1872.check
index ef84ef79e0..c5dc2a8080 100644
--- a/test/files/neg/t1872.check
+++ b/test/files/neg/t1872.check
@@ -1,4 +1,8 @@
+t1872.scala:3: warning: fruitless type test: a value of type Int cannot also be a scala.util.Random
+  def f(x: Int) = x.isInstanceOf[util.Random]
+                                ^
 t1872.scala:3: error: isInstanceOf cannot test if value types are references.
   def f(x: Int) = x.isInstanceOf[util.Random]
                     ^
+one warning found
 one error found
diff --git a/test/files/neg/t4302.check b/test/files/neg/t4302.check
index 327425acb0..450d28bbc5 100644
--- a/test/files/neg/t4302.check
+++ b/test/files/neg/t4302.check
@@ -1,4 +1,4 @@
-t4302.scala:2: error: abstract type T in type T is unchecked since it is eliminated by erasure
+t4302.scala:2: error: abstract type T is unchecked since it is eliminated by erasure
   def hasMatch[T](x: AnyRef) = x.isInstanceOf[T]
                                              ^
 one error found
diff --git a/test/files/neg/t5762.check b/test/files/neg/t5762.check
new file mode 100644
index 0000000000..10064032aa
--- /dev/null
+++ b/test/files/neg/t5762.check
@@ -0,0 +1,13 @@
+t5762.scala:6: error: non-variable type argument Int in type pattern D[Int] is unchecked since it is eliminated by erasure
+    case _: D[Int]    if bippy => 1
+            ^
+t5762.scala:7: error: non-variable type argument String in type pattern D[String] is unchecked since it is eliminated by erasure
+    case _: D[String]          => 2
+            ^
+t5762.scala:20: error: non-variable type argument D[Int] in type pattern D[D[Int]] is unchecked since it is eliminated by erasure
+    case _: D[D[Int]]    if bippy => 1
+            ^
+t5762.scala:21: error: non-variable type argument D[String] in type pattern D[D[String]] is unchecked since it is eliminated by erasure
+    case _: D[D[String]]          => 2
+            ^
+four errors found
diff --git a/test/files/neg/t5762.flags b/test/files/neg/t5762.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/t5762.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/t5762.scala b/test/files/neg/t5762.scala
new file mode 100644
index 0000000000..fb73552b12
--- /dev/null
+++ b/test/files/neg/t5762.scala
@@ -0,0 +1,24 @@
+class D[-A]
+
+object Test {
+  var bippy: Boolean = true
+  def f1(x: D[Int with String]) = x match {
+    case _: D[Int]    if bippy => 1
+    case _: D[String]          => 2
+  }
+  // Correctly warns:
+  //
+  // a.scala:5: warning: non variable type-argument Int in type pattern D[Int] is unchecked since it is eliminated by erasure
+  //     case _: D[Int]    => 1
+  //             ^
+  // a.scala:6: warning: non variable type-argument String in type pattern D[String] is unchecked since it is eliminated by erasure
+  //     case _: D[String] => 2
+  //             ^
+  // two warnings found
+
+  def f2(x: D[D[Int] with D[String]]) = x match {
+    case _: D[D[Int]]    if bippy => 1
+    case _: D[D[String]]          => 2
+  }
+  // No warnings!
+}
diff --git a/test/files/neg/unchecked-abstract.check b/test/files/neg/unchecked-abstract.check
new file mode 100644
index 0000000000..dc7a8d93d0
--- /dev/null
+++ b/test/files/neg/unchecked-abstract.check
@@ -0,0 +1,25 @@
+unchecked-abstract.scala:16: error: abstract type H in type Con[M.this.H] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Con[H]])
+                                       ^
+unchecked-abstract.scala:21: error: abstract type H in type Con[M.this.H] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Con[H]])
+                                       ^
+unchecked-abstract.scala:27: error: abstract type T in type Inv[M.this.T] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Inv[T]])
+                                       ^
+unchecked-abstract.scala:28: error: abstract type L in type Inv[M.this.L] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Inv[L]])
+                                       ^
+unchecked-abstract.scala:31: error: abstract type H in type Inv[M.this.H] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Inv[H]])
+                                       ^
+unchecked-abstract.scala:33: error: abstract type L in type Inv[M.this.L] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Inv[L]])
+                                       ^
+unchecked-abstract.scala:36: error: abstract type H in type Inv[M.this.H] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Inv[H]])
+                                       ^
+unchecked-abstract.scala:37: error: abstract type T in type Inv[M.this.T] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Inv[T]])
+                                       ^
+8 errors found
diff --git a/test/files/neg/unchecked-abstract.flags b/test/files/neg/unchecked-abstract.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/unchecked-abstract.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/unchecked-abstract.scala b/test/files/neg/unchecked-abstract.scala
new file mode 100644
index 0000000000..5b915755f4
--- /dev/null
+++ b/test/files/neg/unchecked-abstract.scala
@@ -0,0 +1,93 @@
+trait Con[-X]
+trait Inv[X]
+trait Cov[+X]
+
+abstract class M {
+  type H
+  type L <: H
+  type T >: L <: H
+
+  def h1(x: Con[H]) = {
+    /* nowarn */ println(x.isInstanceOf[Con[H]])
+    /* nowarn */ println(x.isInstanceOf[Con[T]])
+    /* nowarn */ println(x.isInstanceOf[Con[L]])
+  }
+  def h2(x: Con[T]) = {
+    /*   warn */ println(x.isInstanceOf[Con[H]])
+    /* nowarn */ println(x.isInstanceOf[Con[T]])
+    /* nowarn */ println(x.isInstanceOf[Con[L]])
+  }
+  def h3(x: Con[L]) = {
+    /*   warn */ println(x.isInstanceOf[Con[H]])
+    /*   warn */ println(x.isInstanceOf[Con[T]])
+    /* nowarn */ println(x.isInstanceOf[Con[L]])
+  }
+  def h4(x: Inv[H]) = {
+    /* nowarn */ println(x.isInstanceOf[Inv[H]])
+    /*   warn */ println(x.isInstanceOf[Inv[T]])
+    /*   warn */ println(x.isInstanceOf[Inv[L]])
+  }
+  def h5(x: Inv[T]) = {
+    /*   warn */ println(x.isInstanceOf[Inv[H]])
+    /* nowarn */ println(x.isInstanceOf[Inv[T]])
+    /*   warn */ println(x.isInstanceOf[Inv[L]])
+  }
+  def h6(x: Inv[L]) = {
+    /*   warn */ println(x.isInstanceOf[Inv[H]])
+    /*   warn */ println(x.isInstanceOf[Inv[T]])
+    /* nowarn */ println(x.isInstanceOf[Inv[L]])
+  }
+  def h7(x: Cov[H]) = {
+    /* nowarn */ println(x.isInstanceOf[Cov[H]])
+    /*   warn */ println(x.isInstanceOf[Cov[T]])
+    /*   warn */ println(x.isInstanceOf[Cov[L]])
+  }
+  def h8(x: Cov[T]) = {
+    /* nowarn */ println(x.isInstanceOf[Cov[H]])
+    /* nowarn */ println(x.isInstanceOf[Cov[T]])
+    /*   warn */ println(x.isInstanceOf[Cov[L]])
+  }
+  def h9(x: Cov[L]) = {
+    /* nowarn */ println(x.isInstanceOf[Cov[H]])
+    /* nowarn */ println(x.isInstanceOf[Cov[T]])
+    /* nowarn */ println(x.isInstanceOf[Cov[L]])
+  }
+}
+
+object Test extends M {
+  type H = Any
+  type T = Int
+  type L = Nothing
+
+  val conh = new Con[H] { }
+  val cont = new Con[T] { }
+  val conl = new Con[L] { }
+
+  val invh = new Inv[H] { }
+  val invt = new Inv[T] { }
+  val invl = new Inv[L] { }
+
+  val covh = new Cov[H] { }
+  val covt = new Cov[T] { }
+  val covl = new Cov[L] { }
+
+  def main(args: Array[String]): Unit = {
+    h1(conh)
+    h2(conh)
+    h2(cont)
+    h3(conh)
+    h3(cont)
+    h3(conl)
+
+    h4(invh)
+    h5(invt)
+    h6(invl)
+
+    h7(covh)
+    h7(covt)
+    h7(covl)
+    h8(covt)
+    h8(covl)
+    h9(covl)
+  }
+}
diff --git a/test/files/neg/unchecked-impossible.check b/test/files/neg/unchecked-impossible.check
new file mode 100644
index 0000000000..0ab371dbaa
--- /dev/null
+++ b/test/files/neg/unchecked-impossible.check
@@ -0,0 +1,4 @@
+unchecked-impossible.scala:5: error: fruitless type test: a value of type T2[Int,Int] cannot also be a Seq[A]
+    case Seq(x) =>
+            ^
+one error found
diff --git a/test/files/neg/unchecked-impossible.flags b/test/files/neg/unchecked-impossible.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/unchecked-impossible.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/unchecked-impossible.scala b/test/files/neg/unchecked-impossible.scala
new file mode 100644
index 0000000000..985a2d0b08
--- /dev/null
+++ b/test/files/neg/unchecked-impossible.scala
@@ -0,0 +1,16 @@
+final case class T2[+A, +B](a: A, b: B)
+
+class A {
+  def f1 = T2(1, 2) match {
+    case Seq(x) =>
+    case _      =>
+  }
+  def f2 = T2(1, 2) match {
+    case _: T2[Int, Int] => /* nowarn */
+    case _               =>
+  }
+  def f3 = T2(1, 2) match {
+    case _: T2[_, Int] => /* nowarn */
+    case _             =>
+  }
+}
diff --git a/test/files/neg/unchecked-knowable.check b/test/files/neg/unchecked-knowable.check
new file mode 100644
index 0000000000..3a6ef994b5
--- /dev/null
+++ b/test/files/neg/unchecked-knowable.check
@@ -0,0 +1,4 @@
+unchecked-knowable.scala:17: error: fruitless type test: a value of type Bippy cannot also be a A1
+  /*   warn */ (new Bippy).isInstanceOf[A1]
+                                       ^
+one error found
diff --git a/test/files/neg/unchecked-knowable.flags b/test/files/neg/unchecked-knowable.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/unchecked-knowable.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/unchecked-knowable.scala b/test/files/neg/unchecked-knowable.scala
new file mode 100644
index 0000000000..667b47f504
--- /dev/null
+++ b/test/files/neg/unchecked-knowable.scala
@@ -0,0 +1,20 @@
+/** Knowable - only final leaves */
+sealed abstract class A1
+sealed abstract class A2 extends A1
+final class A3 extends A1
+final class A4 extends A2
+
+/** Unknowable */
+sealed abstract class B1
+sealed abstract class B2 extends B1
+final class B3 extends B1
+trait B4 extends B2
+
+class Bippy
+trait Dingus
+
+class A {
+  /*   warn */ (new Bippy).isInstanceOf[A1]
+  /* nowarn */ (new Bippy).isInstanceOf[B1]
+  /* nowarn */ ((new Bippy): Any).isInstanceOf[A1]
+}
diff --git a/test/files/neg/unchecked-refinement.check b/test/files/neg/unchecked-refinement.check
new file mode 100644
index 0000000000..d81517464f
--- /dev/null
+++ b/test/files/neg/unchecked-refinement.check
@@ -0,0 +1,13 @@
+unchecked-refinement.scala:17: error: abstract type U in type pattern Foo[U,U,V] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Foo[U, U, V] if b       => ()
+                         ^
+unchecked-refinement.scala:19: error: non-variable type argument Any in type pattern Foo[Any,U,V] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Foo[Any, U, V] if b     => ()
+                         ^
+unchecked-refinement.scala:23: error: a pattern match on a refinement type is unchecked
+    /* nowarn - todo */ case x: AnyRef { def bippy: Int } if b => x.bippy  // this could/should do an instance check and not warn
+                                ^
+unchecked-refinement.scala:24: error: a pattern match on a refinement type is unchecked
+    /* nowarn - todo */ case x: AnyRef { def size: Int } if b  => x.size   // this could/should do a static conformance test and not warn
+                                ^
+four errors found
diff --git a/test/files/neg/unchecked-refinement.flags b/test/files/neg/unchecked-refinement.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/unchecked-refinement.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/unchecked-refinement.scala b/test/files/neg/unchecked-refinement.scala
new file mode 100644
index 0000000000..79ed7f13c1
--- /dev/null
+++ b/test/files/neg/unchecked-refinement.scala
@@ -0,0 +1,27 @@
+// a.scala
+// Thu Sep 27 09:42:16 PDT 2012
+
+trait Bar[-T1, T2, +T3] { }
+trait Foo[-T1, T2, +T3] extends Bar[T1, T2, T3]
+
+class A {
+  var b = true
+
+  def f1(x: Foo[Int, Int, Int]) = x match {
+    /* nowarn */ case _: Foo[Nothing, Int, Any] => true
+  }
+  def f2[T, U, V](x: Foo[T, U, V]) = x match {
+    /* nowarn */ case _: Foo[Nothing, U, Any] => true
+  }
+  def f3[T, U, V](x: Foo[T, U, V]) = x match {
+    /*   warn */ case _: Foo[U, U, V] if b       => ()
+    /* nowarn */ case _: Foo[Nothing, U, V] if b => ()
+    /*   warn */ case _: Foo[Any, U, V] if b     => ()
+  }
+
+  def f4(xs: List[Int]) = xs match {
+    /* nowarn - todo */ case x: AnyRef { def bippy: Int } if b => x.bippy  // this could/should do an instance check and not warn
+    /* nowarn - todo */ case x: AnyRef { def size: Int } if b  => x.size   // this could/should do a static conformance test and not warn
+    /* nowarn */ case x: ((AnyRef { def size: Int }) @unchecked) if b  => x.size
+  }
+}
diff --git a/test/files/neg/unchecked.check b/test/files/neg/unchecked.check
index 34a11db1a0..2883b716c9 100644
--- a/test/files/neg/unchecked.check
+++ b/test/files/neg/unchecked.check
@@ -2,7 +2,7 @@ unchecked.scala:18: error: non-variable type argument String in type pattern Ite
     case xs: Iterable[String] => xs.head // unchecked
              ^
 unchecked.scala:22: error: non-variable type argument Any in type pattern Set[Any] is unchecked since it is eliminated by erasure
-    case xs: Set[Any]    => xs.head // unchecked
+    case xs: Set[Any] => xs.head // unchecked
              ^
 unchecked.scala:26: error: non-variable type argument Any in type pattern Map[Any,Any] is unchecked since it is eliminated by erasure
     case xs: Map[Any, Any] => xs.head // unchecked
diff --git a/test/files/neg/unchecked.scala b/test/files/neg/unchecked.scala
index b50cdf9d7a..e491b253ba 100644
--- a/test/files/neg/unchecked.scala
+++ b/test/files/neg/unchecked.scala
@@ -19,8 +19,8 @@ object Test {
     case _                    => 0
   }
   def f3(x: Any) = x match {
-    case xs: Set[Any]    => xs.head // unchecked
-    case _                    => 0
+    case xs: Set[Any] => xs.head // unchecked
+    case _            => 0
   }
   def f4(x: Any) = x match {
     case xs: Map[Any, Any] => xs.head // unchecked
diff --git a/test/files/neg/unchecked2.check b/test/files/neg/unchecked2.check
index e37865928e..68fdfa82ac 100644
--- a/test/files/neg/unchecked2.check
+++ b/test/files/neg/unchecked2.check
@@ -1,19 +1,43 @@
-unchecked2.scala:2: error: non-variable type argument Int in type Option[Int] is unchecked since it is eliminated by erasure
-  Some(123).isInstanceOf[Option[Int]]
-                        ^
-unchecked2.scala:3: error: non-variable type argument String in type Option[String] is unchecked since it is eliminated by erasure
-  Some(123).isInstanceOf[Option[String]]
-                        ^
-unchecked2.scala:4: error: non-variable type argument List[String] in type Option[List[String]] is unchecked since it is eliminated by erasure
-  Some(123).isInstanceOf[Option[List[String]]]
-                        ^
-unchecked2.scala:5: error: non-variable type argument List[Int => String] in type Option[List[Int => String]] is unchecked since it is eliminated by erasure
-  Some(123).isInstanceOf[Option[List[Int => String]]]
-                        ^
-unchecked2.scala:6: error: non-variable type argument (String, Double) in type Option[(String, Double)] is unchecked since it is eliminated by erasure
-  Some(123).isInstanceOf[Option[(String, Double)]]
-                        ^
-unchecked2.scala:7: error: non-variable type argument String => Double in type Option[String => Double] is unchecked since it is eliminated by erasure
-  Some(123).isInstanceOf[Option[String => Double]]
-                        ^
-6 errors found
+unchecked2.scala:4: error: fruitless type test: a value of type Some[List[Int]] cannot also be a Option[List[String]] (but still might match its erasure)
+  /*   warn */ Some(List(1)).isInstanceOf[Option[List[String]]]
+                                         ^
+unchecked2.scala:5: error: non-variable type argument Option[_] in type Option[Option[_]] is unchecked since it is eliminated by erasure
+  /*   warn */ Some(123).isInstanceOf[Option[Option[_]]]
+                                     ^
+unchecked2.scala:6: error: fruitless type test: a value of type Some[Int] cannot also be a Option[String] (but still might match its erasure)
+  /*   warn */ Some(123).isInstanceOf[Option[String]]
+                                     ^
+unchecked2.scala:7: error: fruitless type test: a value of type Some[Int] cannot also be a Option[List[String]] (but still might match its erasure)
+  /*   warn */ Some(123).isInstanceOf[Option[List[String]]]
+                                     ^
+unchecked2.scala:8: error: fruitless type test: a value of type Some[Int] cannot also be a Option[List[Int => String]] (but still might match its erasure)
+  /*   warn */ Some(123).isInstanceOf[Option[List[Int => String]]]
+                                     ^
+unchecked2.scala:9: error: fruitless type test: a value of type Some[Int] cannot also be a Option[(String, Double)] (but still might match its erasure)
+  /*   warn */ Some(123).isInstanceOf[Option[(String, Double)]]
+                                     ^
+unchecked2.scala:10: error: fruitless type test: a value of type Some[Int] cannot also be a Option[String => Double] (but still might match its erasure)
+  /*   warn */ Some(123).isInstanceOf[Option[String => Double]]
+                                     ^
+unchecked2.scala:14: error: non-variable type argument List[String] in type Option[List[String]] is unchecked since it is eliminated by erasure
+  /*   warn */ (Some(List(1)): Any).isInstanceOf[Option[List[String]]]
+                                                ^
+unchecked2.scala:15: error: non-variable type argument Int in type Option[Int] is unchecked since it is eliminated by erasure
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[Int]]
+                                            ^
+unchecked2.scala:16: error: non-variable type argument String in type Option[String] is unchecked since it is eliminated by erasure
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[String]]
+                                            ^
+unchecked2.scala:17: error: non-variable type argument List[String] in type Option[List[String]] is unchecked since it is eliminated by erasure
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[List[String]]]
+                                            ^
+unchecked2.scala:18: error: non-variable type argument List[Int => String] in type Option[List[Int => String]] is unchecked since it is eliminated by erasure
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[List[Int => String]]]
+                                            ^
+unchecked2.scala:19: error: non-variable type argument (String, Double) in type Option[(String, Double)] is unchecked since it is eliminated by erasure
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[(String, Double)]]
+                                            ^
+unchecked2.scala:20: error: non-variable type argument String => Double in type Option[String => Double] is unchecked since it is eliminated by erasure
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[String => Double]]
+                                            ^
+14 errors found
diff --git a/test/files/neg/unchecked2.scala b/test/files/neg/unchecked2.scala
index a2e757e1dc..616b05aad8 100644
--- a/test/files/neg/unchecked2.scala
+++ b/test/files/neg/unchecked2.scala
@@ -1,8 +1,33 @@
 object Test {
-  Some(123).isInstanceOf[Option[Int]]
-  Some(123).isInstanceOf[Option[String]]
-  Some(123).isInstanceOf[Option[List[String]]]
-  Some(123).isInstanceOf[Option[List[Int => String]]]
-  Some(123).isInstanceOf[Option[(String, Double)]]
-  Some(123).isInstanceOf[Option[String => Double]]
+  // These warn because it can be statically shown they won't match.
+
+  /*   warn */ Some(List(1)).isInstanceOf[Option[List[String]]]
+  /*   warn */ Some(123).isInstanceOf[Option[Option[_]]]
+  /*   warn */ Some(123).isInstanceOf[Option[String]]
+  /*   warn */ Some(123).isInstanceOf[Option[List[String]]]
+  /*   warn */ Some(123).isInstanceOf[Option[List[Int => String]]]
+  /*   warn */ Some(123).isInstanceOf[Option[(String, Double)]]
+  /*   warn */ Some(123).isInstanceOf[Option[String => Double]]
+
+  // These warn because you can't check at runtime.
+
+  /*   warn */ (Some(List(1)): Any).isInstanceOf[Option[List[String]]]
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[Int]]
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[String]]
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[List[String]]]
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[List[Int => String]]]
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[(String, Double)]]
+  /*   warn */ (Some(123): Any).isInstanceOf[Option[String => Double]]
+
+  // These don't warn.
+
+  /* nowarn */ Some(List(1)).isInstanceOf[Option[List[Int]]]
+  /* nowarn */ Some(123).isInstanceOf[Option[Int]]
+  /* nowarn */ Some(123).isInstanceOf[Some[Int]]
+  /* nowarn */ Some(123).isInstanceOf[AnyRef]
+
+  /* nowarn */ (Some(List(1)): Any).isInstanceOf[Option[_]]
+  /* nowarn */ (Some(123): Any).isInstanceOf[Option[_]]
+  /* nowarn */ (Some(123): Any).isInstanceOf[Some[_]]
+  /* nowarn */ (Some(123): Any).isInstanceOf[AnyRef]
 }
diff --git a/test/files/neg/unchecked3.check b/test/files/neg/unchecked3.check
new file mode 100644
index 0000000000..f4f0c74257
--- /dev/null
+++ b/test/files/neg/unchecked3.check
@@ -0,0 +1,37 @@
+unchecked3.scala:24: error: non-variable type argument Double in type pattern E1[Double] is unchecked since it is eliminated by erasure
+  /*   warn */ def peerTypes2(x: B1[Int]) = x match { case _: E1[Double] => true }
+                                                              ^
+unchecked3.scala:25: error: non-variable type argument Double in type pattern F1[Double] is unchecked since it is eliminated by erasure
+  /*   warn */ def peerTypes3(x: B1[_]) = x match { case _: F1[Double] => true }
+                                                            ^
+unchecked3.scala:28: error: non-variable type argument Int in type pattern A2[Int] is unchecked since it is eliminated by erasure
+  /*   warn */ def twotypes1[T](x: B2[T, Int]) = x match { case _: A2[Int] => true }
+                                                                   ^
+unchecked3.scala:32: error: non-variable type argument Int in type pattern B2[_,Int] is unchecked since it is eliminated by erasure
+  /*   warn */ def twotypes5[T](x: A2[T]) = x match { case _: B2[_, Int] => true }
+                                                              ^
+unchecked3.scala:40: error: non-variable type argument String in type pattern Array[List[String]] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Array[List[String]]         => ()
+                         ^
+unchecked3.scala:43: error: non-variable type argument String in type pattern Array[Array[List[String]]] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Array[Array[List[String]]]  => ()
+                         ^
+unchecked3.scala:50: error: non-variable type argument String in type pattern Array[List[String]] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Array[List[String]]         => ()
+                         ^
+unchecked3.scala:53: error: non-variable type argument String in type pattern Array[Array[List[String]]] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Array[Array[List[String]]]  => ()
+                         ^
+unchecked3.scala:60: error: non-variable type argument String in type pattern Array[List[String]] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Array[List[String]]        => ()
+                         ^
+unchecked3.scala:62: error: non-variable type argument Array[String] in type pattern Array[List[Array[String]]] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Array[List[Array[String]]] => ()
+                         ^
+unchecked3.scala:63: error: non-variable type argument String in type pattern Array[Array[List[String]]] is unchecked since it is eliminated by erasure
+    /*   warn */ case _: Array[Array[List[String]]] => ()
+                         ^
+unchecked3.scala:75: error: abstract type A in type pattern Set[Q.this.A] is unchecked since it is eliminated by erasure
+      /*   warn */ case xs: Set[A]  => xs.head
+                            ^
+12 errors found
diff --git a/test/files/neg/unchecked3.flags b/test/files/neg/unchecked3.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/unchecked3.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/unchecked3.scala b/test/files/neg/unchecked3.scala
new file mode 100644
index 0000000000..7b8c13e8f8
--- /dev/null
+++ b/test/files/neg/unchecked3.scala
@@ -0,0 +1,83 @@
+sealed trait A2[T1]
+final class B2[T1, T2] extends A2[T1]
+
+sealed trait A[T]
+final class B[T] extends A[T]
+
+sealed trait A1[T]
+trait B1[T] extends A1[T]
+trait C1[T] extends A1[T]
+trait D1[T] extends A1[Int]
+trait E1[T] extends B1[Int]
+trait F1[T] extends B1[T]
+
+object MiscUnchecked {
+  /* nowarn */ def knownType1(x: A[Int])  = x match { case _: B[Int] if true => 1 }
+  /* nowarn */ def knownType2(x: B[Int])  = x match { case _: A[Int] if true => 1 }
+  /* nowarn */ def tparamLeakage1(x: Any) = x match { case Array() => 1 }
+  /* nowarn */ def tparamLeakage2(x: Any) = x match { case List() => 1 }
+
+  // E1[Double] implies B1[Int], but B1[Int] does not imply E1[Double], even if .isInstanceOf[E1[_]]
+  // F1[Int] implies B1[Int], and B1[Int] implies F1[Int]
+
+  /* nowarn */ def peerTypes1(x: B1[Int]) = x match { case _: C1[Int] => true }
+  /*   warn */ def peerTypes2(x: B1[Int]) = x match { case _: E1[Double] => true }
+  /*   warn */ def peerTypes3(x: B1[_]) = x match { case _: F1[Double] => true }
+  /* nowarn */ def peerTypes4(x: B1[Int]) = x match { case _: F1[Int] => true }
+
+  /*   warn */ def twotypes1[T](x: B2[T, Int]) = x match { case _: A2[Int] => true }
+  /* nowarn */ def twotypes2[T](x: B2[Int, T]) = x match { case _: A2[Int] => true }
+  /* nowarn */ def twotypes3(x: A2[Int]) = x match { case _: B2[Int, _] => true }
+  /* nowarn */ def twotypes4[T](x: A2[T]) = x match { case _: B2[T, _] => true }
+  /*   warn */ def twotypes5[T](x: A2[T]) = x match { case _: B2[_, Int] => true }
+}
+
+object Arrays {
+  def f1(x: Any) = x match {
+    /* nowarn */ case _: Array[Int]                  => ()
+    /* nowarn */ case _: Array[Boolean]              => ()
+    /* nowarn */ case _: Array[String]               => ()
+    /*   warn */ case _: Array[List[String]]         => ()
+    /* nowarn */ case _: Array[Array[String]]        => ()
+    /* nowarn */ case _: Array[Array[Array[String]]] => ()
+    /*   warn */ case _: Array[Array[List[String]]]  => ()
+  }
+
+  def f2(x: Array[_]) = x match {
+    /* nowarn */ case _: Array[Int]                  => ()
+    /* nowarn */ case _: Array[Boolean]              => ()
+    /* nowarn */ case _: Array[String]               => ()
+    /*   warn */ case _: Array[List[String]]         => ()
+    /* nowarn */ case _: Array[Array[String]]        => ()
+    /* nowarn */ case _: Array[Array[Array[String]]] => ()
+    /*   warn */ case _: Array[Array[List[String]]]  => ()
+  }
+
+  def f3[T](x: Array[T]) = x match {
+    /* nowarn */ case _: Array[Int]                 => ()
+    /* nowarn */ case _: Array[Boolean]             => ()
+    /* nowarn */ case _: Array[String]              => ()
+    /*   warn */ case _: Array[List[String]]        => ()
+    /* nowarn */ case _: Array[Array[String]]       => ()
+    /*   warn */ case _: Array[List[Array[String]]] => ()
+    /*   warn */ case _: Array[Array[List[String]]] => ()
+  }
+}
+
+object Matching {
+  class Q {
+    type A
+    type B <: A
+
+    def f(xs: Traversable[B]) = xs match {
+      /* nowarn */ case xs: List[A] => xs.head
+      /* nowarn */ case xs: Seq[B]  => xs.head
+      /*   warn */ case xs: Set[A]  => xs.head
+    }
+    def f2[T <: B](xs: Traversable[T]) = xs match {
+      /* nowarn */ case xs: List[B with T] => xs.head
+      /* nowarn */ case xs: Seq[A]         => xs.head
+      /* nowarn */ case xs: Set[T]         => xs.head
+    }
+  }
+}
diff --git a/test/files/pos/t1107/O.scala b/test/files/pos/t1107b/O.scala
index aa605a6d09..aa605a6d09 100644
--- a/test/files/pos/t1107/O.scala
+++ b/test/files/pos/t1107b/O.scala
diff --git a/test/files/pos/t1107/T.scala b/test/files/pos/t1107b/T.scala
index 1f3712d529..1f3712d529 100644
--- a/test/files/pos/t1107/T.scala
+++ b/test/files/pos/t1107b/T.scala
diff --git a/test/files/pos/t1203/J.java b/test/files/pos/t1203b/J.java
index 7fae118e04..7fae118e04 100644
--- a/test/files/pos/t1203/J.java
+++ b/test/files/pos/t1203b/J.java
diff --git a/test/files/pos/t1203/S.scala b/test/files/pos/t1203b/S.scala
index 68eac4bf6d..68eac4bf6d 100644
--- a/test/files/pos/t1203/S.scala
+++ b/test/files/pos/t1203b/S.scala
diff --git a/test/files/pos/t6275.flags b/test/files/pos/t6275.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/pos/t6275.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/pos/t6275.scala b/test/files/pos/t6275.scala
new file mode 100644
index 0000000000..6b5ec7dceb
--- /dev/null
+++ b/test/files/pos/t6275.scala
@@ -0,0 +1,11 @@
+
+sealed trait A[T]
+final class B[T] extends A[T]
+
+object ParsedAxis {
+  type BI = B[Int]
+
+  def f1(a: A[Int]) = a match { case b: B[Int] => 3 }
+  def f2(a: A[Int]) = a match { case b: BI => 3 }
+  def f3(a: A[Int]) = a match { case b: B[t] => 3 }
+}
diff --git a/test/files/run/t576.scala b/test/files/run/t576.scala
index dc09d8dc98..756a241572 100644
--- a/test/files/run/t576.scala
+++ b/test/files/run/t576.scala
@@ -12,7 +12,7 @@ object Dingus {
 object Test {
   val x1 = new A
   val x2 = new A
-  
+
   val x3 = new { self =>
     override def equals(other : Any) = other match {
       case that: self.type    => true
@@ -20,7 +20,7 @@ object Test {
     }
   }
   val x4 = new { self =>
-    def f(x: Any) = x match {
+    def f(x: Any): Int = x match {
       case _: x1.type     => 1
       case _: x2.type     => 2
       case _: x3.type     => 3
@@ -35,11 +35,11 @@ object Test {
     assert(x1 != x2)
     assert(x1 != ())
     assert(x2 != x1)
-    
+
     assert(x3 == x3)
     assert(x3 != x2)
     assert(x2 != x3)
-    
+
     List(x1, x2, x3, x4, Dingus) map x4.f foreach println
   }
-}
\ No newline at end of file
+}
diff --git a/test/pending/pos/exhaust_2.scala b/test/pending/pos/exhaust_2.scala
new file mode 100644
index 0000000000..4f4e47c43b
--- /dev/null
+++ b/test/pending/pos/exhaust_2.scala
@@ -0,0 +1,54 @@
+object ExhaustivityWarnBugReportMinimal {
+  //sealed is needed for the warning
+  sealed trait FoundNode[T]/*presence of parameters is irrelevant*/
+  // This also causes a warning:
+  // sealed abstract class FoundNode[T]/*presence of parameters is irrelevant*/
+  case class FoundFilter[T](/*presence of parameters is irrelevant*/) extends FoundNode[T]
+  case class FoundTypeCase[T](/*presence of parameters is irrelevant*/) extends FoundNode[T]
+  val f: Some[_] = ???
+  f match {
+    case x: Some[t] => //no warning
+  }
+  //With these variants, no warnings:
+  //val v: (Some[Int], FoundNode[_]) = (???, ???)
+  //val v: (Some[AnyRef], FoundNode[_]) = (???, ???)
+  //val v: (Some[String], FoundNode[_]) = (???, ???)
+
+  val v: (Some[_], FoundNode[_]) = (???, ???)
+  //Warning here:
+  v match {
+    case (x: Some[t], _: FoundNode[_]) =>
+  }
+  v match {
+    case (x: Some[t], _) =>
+  }
+
+  v match {
+    case (x: Some[_], _) =>
+  }
+  case class Foo[T]()
+
+  val vp: (Foo[_], FoundNode[_]) = (???, ???)
+  vp match {
+    case (x: Foo[_], _) =>
+  }
+
+  //No warning here:
+  v match {
+    case (Some(y), _) =>
+  }
+
+  v match {
+    case (x, _) =>
+  }
+
+  val v2: (Some[_], Int) = (???, ???)
+  v2 match {
+    case (x: Some[t], _) =>
+  }
+
+  val v3: (Option[_], FoundNode[_]) = (???, ???)
+  v match {
+    case (x: Option[_], _) =>
+  }
+}