Add a test for structural typing

demos/Demo.Struct/module.nml

@@ -0,0 +1,12 @@
+// Test structural typing
+// see https://github.com/nstack/nstack-server/issues/571
+module Demo.Struct:0.0.1-SNAPSHOT
+
+type V1 = A Integer
+        | B { b1 : Integer, b2 : Text, b3 : Boolean }
+type V2 = B { b3 : Boolean, b2 : Text, b1 : Integer }
+        | A Integer
+
+fun test0 : V1 -> Integer
+
+def test1 = Conv.from_json<V2> | test0

demos/Demo.Struct/nstack.yaml

@@ -0,0 +1,15 @@
+# The language stack to use
+stack: Python
+
+# Parent Image
+parent: nstack/NStack.Python:0.25.0
+
+# (Optional) System-level packages needed
+packages: []
+
+# (Optional) Commands to run when building the service (Bash-compatible)
+commands: []
+
+# (Optional) Files/Dir to copy across into the service (can use regex/glob syntax)
+files: []
+

demos/Demo.Struct/service.py

@@ -0,0 +1,10 @@
+#!/usr/bin/env python3
+"""
+Demo.Struct:0.0.1-SNAPSHOT Service
+"""
+import nstack
+
+class Service(nstack.BaseService):
+    def numChars(self, x):
+        return 0
+

demos/nstack-test-Demos.yaml

@@ -4,6 +4,7 @@ module_dirs:
   - Demo.NumChars
   - Demo.DigitString
   - Demo.Workflow
+  - Demo.Struct
 
 tests:
   - name: demo_classify