Fix #1501 - Check trait inheritance condition

We need to check a coherence condition between the superclass
of a trait and the superclass of an inheriting class or trait.

1 files changed, 18 insertions, 0 deletions

diff --git a/tests/neg/i1501.scala b/tests/neg/i1501.scala
new file mode 100644
index 000000000..045f2be1d
--- /dev/null
+++ b/tests/neg/i1501.scala
@@ -0,0 +1,18 @@
+class A {
+  def foo: Int = 1
+}
+
+trait B extends A
+
+abstract class D {
+  def foo: Int
+}
+
+class C extends D with B // error: illegal trait inheritance
+trait E extends D with B // error: illegal trait inheritance
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    println(new C().foo)
+  }
+}