Merge pull request #1921 from dotty-staging/fix-#1907

Fix #1907: Improve error message

3 files changed, 36 insertions, 2 deletions

diff --git a/tests/neg/i1802.scala b/tests/neg/i1802.scala
index 56da672a8..93e790f18 100644
--- a/tests/neg/i1802.scala
+++ b/tests/neg/i1802.scala
@@ -14,8 +14,8 @@ object Exception {
     def apply(x: Throwable): T = f(downcast(x).get)
   }
 
-  def mkThrowableCatcher[T](isDef: Throwable => Boolean, f: Throwable => T) = mkCatcher(isDef, f)
+  def mkThrowableCatcher[T](isDef: Throwable => Boolean, f: Throwable => T) = mkCatcher(isDef, f) // error: undetermined ClassTag
 
-  implicit def throwableSubtypeToCatcher[Ex <: Throwable: ClassTag, T](pf: PartialFunction[Ex, T]) = // error: cyclic reference
+  implicit def throwableSubtypeToCatcher[Ex <: Throwable: ClassTag, T](pf: PartialFunction[Ex, T]) =
     mkCatcher(pf.isDefinedAt _, pf.apply _)
 }
diff --git a/tests/neg/i1907.scala b/tests/neg/i1907.scala
new file mode 100644
index 000000000..6bc3bb56f
--- /dev/null
+++ b/tests/neg/i1907.scala
@@ -0,0 +1,7 @@
+import java.io.File
+
+object Test {
+  Some(new File("."))
+    .map(_.listFiles).getOrElse(Array.empty) // error: undetermined ClassTag
+    .map(_.listFiles)
+}
diff --git a/tests/neg/undet-classtag.scala b/tests/neg/undet-classtag.scala
new file mode 100644
index 000000000..dfe0eb2db
--- /dev/null
+++ b/tests/neg/undet-classtag.scala
@@ -0,0 +1,27 @@
+import scala.reflect.ClassTag
+
+object Test {
+  def f[T: reflect.ClassTag](x: T) = ???
+
+  f(???) // error: undetermined ClassTag
+}
+
+// SI 9754
+object Program {
+  def test[T: ClassTag](x: T) = {
+    val arr = new Array[T](1)
+    println(arr.getClass)
+    println(x.getClass)
+    arr(0) = x
+  }
+
+  def main(args: Array[String]): Unit = {
+    test(new Array[Nothing](0)) // error: undetermined ClassTag
+  }
+}
+
+// SI 5353
+object t5353 {
+  if (false) Array("qwe") else Array() // error: undetermined ClassTag
+}
+