3 files changed, 19 insertions, 0 deletions
diff --git a/test/files/neg/t8450.check b/test/files/neg/t8450.check
new file mode 100644
index 0000000000..eeabb9730c
--- /dev/null
+++ b/test/files/neg/t8450.check
@@ -0,0 +1,6 @@
+t8450.scala:5: warning: implicit numeric widening
+  def elapsed: Foo = (System.nanoTime - 100L).foo
+                                      ^
+error: No warnings can be incurred under -Xfatal-warnings.
+one warning found
+one error found
diff --git a/test/files/neg/t8450.flags b/test/files/neg/t8450.flags
new file mode 100644
index 0000000000..9a1332d7af
--- /dev/null
+++ b/test/files/neg/t8450.flags
@@ -0,0 +1 @@
+-Ywarn-numeric-widen -Xfatal-warnings
+\ No newline at end of file
diff --git a/test/files/neg/t8450.scala b/test/files/neg/t8450.scala
new file mode 100644
index 0000000000..f20ed2bc31
--- /dev/null
+++ b/test/files/neg/t8450.scala
@@ -0,0 +1,12 @@
+trait Foo
+
+class WarnWidening {
+  implicit class FooDouble(d: Double) { def foo = new Foo {} }
+  def elapsed: Foo = (System.nanoTime - 100L).foo
+}
+
+class NoWarnWidening {
+  implicit class FooLong(l: Long) { def foo = new Foo {} }
+  implicit class FooDouble(d: Double) { def foo = new Foo {} }
+  def elapsed: Foo = (System.nanoTime - 100L).foo
+}