Fix #5793: Add regression test

Author: nicolasstucki

tests/pos/i5793/A.scala

@@ -0,0 +1,11 @@
+object exec{
+  trait Runner[T]{
+    def run(t: T): Unit
+  }
+  object Runner{
+    def run[T: Runner](t: T): Unit = implicitly[Runner[T]].run(t)
+    implicit inline def runImplicitly[T]: Runner[T] = new {
+      def run(t: T) = List(()).map(x => x).head // <<<
+    }
+  }
+}

tests/pos/i5793/B.scala

@@ -0,0 +1,6 @@
+object Main{
+  def main(args: Array[String]): Unit = {
+    import exec._
+    Runner.run(Some(5))
+  }
+}