Allow passing arguments to functions

test/test-run

@@ -30,6 +30,20 @@ testReferingToALightningFunctionWorks() {
   assertContains "$STDOUT" "Good Bye."
 }
 
+testArgumentsArePassedToLightningFunctions() {
+  echo '
+  #!/usr/bin/env bash
+
+  ⚡hello() { echo "Hello, $@!" ; }
+  ' > go
+
+  echo "source $REPO_ROOT/⚡" >> go
+  chmod +x go
+
+  try ./go hello banana
+  assertContains "$STDOUT" "Hello, banana!"
+}
+
 testDefiningALightningFunctionWorksWithSelector16() {
   echo '
   #!/usr/bin/env bash