Add simple interface call test

Author: tanishiking

Diff for: cli/src/main/scala/TestSuites.scala

@@ -7,6 +7,7 @@ object TestSuites {
     TestSuite("testsuite.core.add.Add", "add"),
     TestSuite("testsuite.core.add.Add", "add"),
     TestSuite("testsuite.core.virtualdispatch.VirtualDispatch", "virtualDispatch"),
+    TestSuite("testsuite.core.interfacecall.InterfaceCall", "interfaceCall"),
     TestSuite("testsuite.core.asinstanceof.AsInstanceOfTest", "asInstanceOf"),
     TestSuite("testsuite.core.hijackedclassesmono.HijackedClassesMonoTest", "hijackedClassesMono")
   )

Diff for: test-suite/src/main/scala/testsuite/core/InterfaceCall.scala

@@ -0,0 +1,31 @@
+package testsuite.core.interfacecall
+
+import scala.scalajs.js.annotation._
+
+object InterfaceCall {
+  def main(): Unit = { val _ = test() }
+
+  @JSExportTopLevel("interfaceCall")
+  def test(): Boolean = {
+    val c = new Concrete()
+    c.plus(c.zero, 1) == 1 && c.minus(1, c.zero) == 1
+  }
+
+  class Concrete extends AddSub with Zero {
+    override def zero: Int = 0
+  }
+
+  trait Adder {
+    def plus(a: Int, b: Int) = a + b
+  }
+
+  trait Sub {
+    def minus(a: Int, b: Int): Int = a - b
+  }
+
+  trait AddSub extends Adder with Sub
+
+  trait Zero {
+    def zero: Int
+  }
+}