Merge pull request #4115 from retronym/ticket/8597

SI-8597 Improved pattern unchecked warnings

7 files changed, 90 insertions, 1 deletions

diff --git a/test/files/neg/t8597.check b/test/files/neg/t8597.check
new file mode 100644
index 0000000000..bc945f9191
--- /dev/null
+++ b/test/files/neg/t8597.check
@@ -0,0 +1,21 @@
+t8597.scala:2: warning: abstract type T in type pattern Some[T] is unchecked since it is eliminated by erasure
+  def nowarn[T] = (null: Any) match { case _: Some[T]      => } // warn (did not warn due to SI-8597)
+                                              ^
+t8597.scala:5: warning: abstract type pattern T is unchecked since it is eliminated by erasure
+  def warn1[T]  = (null: Any) match { case _: T            => } // warn
+                                              ^
+t8597.scala:6: warning: non-variable type argument String in type pattern Some[String] is unchecked since it is eliminated by erasure
+  def warn2     = (null: Any) match { case _: Some[String] => } // warn
+                                              ^
+t8597.scala:7: warning: non-variable type argument Unchecked.this.C in type pattern Some[Unchecked.this.C] is unchecked since it is eliminated by erasure
+                  (null: Any) match { case _: Some[C]      => } // warn
+                                              ^
+t8597.scala:18: warning: abstract type T in type pattern Array[T] is unchecked since it is eliminated by erasure
+  def warnArray[T] = (null: Any) match { case _: Array[T] => } // warn (did not warn due to SI-8597)
+                                                 ^
+t8597.scala:26: warning: non-variable type argument String in type pattern Array[Array[List[String]]] is unchecked since it is eliminated by erasure
+  def warnArrayErasure2   = (null: Any) match {case Some(_: Array[Array[List[String]]]) => } // warn
+                                                            ^
+error: No warnings can be incurred under -Xfatal-warnings.
+6 warnings found
+one error found
diff --git a/test/files/neg/t8597.flags b/test/files/neg/t8597.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/t8597.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/t8597.scala b/test/files/neg/t8597.scala
new file mode 100644
index 0000000000..068e87d91a
--- /dev/null
+++ b/test/files/neg/t8597.scala
@@ -0,0 +1,27 @@
+class Unchecked[C] {
+  def nowarn[T] = (null: Any) match { case _: Some[T]      => } // warn (did not warn due to SI-8597)
+
+  // These warned before.
+  def warn1[T]  = (null: Any) match { case _: T            => } // warn
+  def warn2     = (null: Any) match { case _: Some[String] => } // warn
+                  (null: Any) match { case _: Some[C]      => } // warn
+
+  // These must remain without warnings. These are excerpts from
+  // related tests that are more exhauative.
+  class C; class D extends C
+  def okay      = (List(new D) : Seq[D]) match { case _: List[C] => case _ => } // nowarn
+  class B2[A, B]
+  class A2[X] extends B2[X, String]
+  def okay2(x: A2[Int]) = x match { case _: B2[Int, _] => true } // nowarn
+  def okay3(x: A2[Int]) = x match { case _: B2[Int, typeVar] => true } // nowarn
+
+  def warnArray[T] = (null: Any) match { case _: Array[T] => } // warn (did not warn due to SI-8597)
+  def nowarnArrayC   = (null: Any) match { case _: Array[C] => } // nowarn
+
+  def nowarnArrayTypeVar[T] = (null: Any) match { case _: Array[t] => } // nowarn
+
+  def noWarnArrayErasure1 = (null: Any) match {case Some(_: Array[String]) => } // nowarn
+  def noWarnArrayErasure2 = (null: Any) match {case Some(_: Array[List[_]]) => } // nowarn
+  def noWarnArrayErasure3 = (null: Any) match {case Some(_: Array[Array[List[_]]]) => } // nowarn
+  def warnArrayErasure2   = (null: Any) match {case Some(_: Array[Array[List[String]]]) => } // warn
+}
diff --git a/test/files/neg/t8597b.check b/test/files/neg/t8597b.check
new file mode 100644
index 0000000000..3c45a31337
--- /dev/null
+++ b/test/files/neg/t8597b.check
@@ -0,0 +1,6 @@
+t8597b.scala:18: warning: non-variable type argument T in type pattern Some[T] is unchecked since it is eliminated by erasure
+        case _: Some[T] => // warn
+                ^
+error: No warnings can be incurred under -Xfatal-warnings.
+one warning found
+one error found
diff --git a/test/files/neg/t8597b.flags b/test/files/neg/t8597b.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/t8597b.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/t8597b.scala b/test/files/neg/t8597b.scala
new file mode 100644
index 0000000000..b29d591cb1
--- /dev/null
+++ b/test/files/neg/t8597b.scala
@@ -0,0 +1,21 @@
+object Unchecked {
+  (null: Any) match {
+    case _: Some[t] =>
+
+      // t is a fresh pattern type variable, despite our attempts to
+      // backtick our way to the enclosing `t`. Under this interpretation,
+      // the absense of an unchecked warning is expected.
+      (null: Any) match {
+        case _: Some[t] => // no warn
+      }
+      (null: Any) match {
+        case _: Some[`t`] => // no warn
+      }
+
+      // here we correctly issue an unchecked warning
+      type T = t
+      (null: Any) match {
+        case _: Some[T] => // warn
+      }
+  }
+}
diff --git a/test/files/neg/unchecked-abstract.check b/test/files/neg/unchecked-abstract.check
index 72019082ac..703929dca8 100644
--- a/test/files/neg/unchecked-abstract.check
+++ b/test/files/neg/unchecked-abstract.check
@@ -4,6 +4,9 @@ unchecked-abstract.scala:16: warning: abstract type H in type Contravariant[M.th
 unchecked-abstract.scala:21: warning: abstract type H in type Contravariant[M.this.H] is unchecked since it is eliminated by erasure
     /*   warn */ println(x.isInstanceOf[Contravariant[H]])
                                        ^
+unchecked-abstract.scala:22: warning: abstract type T in type Contravariant[M.this.T] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Contravariant[T]])
+                                       ^
 unchecked-abstract.scala:27: warning: abstract type T in type Invariant[M.this.T] is unchecked since it is eliminated by erasure
     /*   warn */ println(x.isInstanceOf[Invariant[T]])
                                        ^
@@ -22,6 +25,15 @@ unchecked-abstract.scala:36: warning: abstract type H in type Invariant[M.this.H
 unchecked-abstract.scala:37: warning: abstract type T in type Invariant[M.this.T] is unchecked since it is eliminated by erasure
     /*   warn */ println(x.isInstanceOf[Invariant[T]])
                                        ^
+unchecked-abstract.scala:42: warning: abstract type T in type Covariant[M.this.T] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Covariant[T]])
+                                       ^
+unchecked-abstract.scala:43: warning: abstract type L in type Covariant[M.this.L] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Covariant[L]])
+                                       ^
+unchecked-abstract.scala:48: warning: abstract type L in type Covariant[M.this.L] is unchecked since it is eliminated by erasure
+    /*   warn */ println(x.isInstanceOf[Covariant[L]])
+                                       ^
 error: No warnings can be incurred under -Xfatal-warnings.
-8 warnings found
+12 warnings found
 one error found