[NF] Add external object connection test.

Belonging to [master]:
  - OpenModelica/OMCompiler#3013
  - #1153

Author: perost

flattening/modelica/scodeinst/ConnectExternalObject1.mo

@@ -0,0 +1,51 @@
+// name: ConnectExternalObject1
+// keywords:
+// status: correct
+// cflags: -d=newInst
+//
+//
+
+class ExtObj
+  extends ExternalObject;
+
+  function constructor
+    output ExtObj obj;
+    external "C" obj = initObject();
+  end constructor;
+
+  function destructor
+    input ExtObj obj;
+    external "C" destroyObject(obj);
+  end destructor;
+end ExtObj;
+
+connector C
+  ExtObj eo;
+end C;
+
+model ConnectExternalObject1
+  C c1, c2;
+equation
+  connect(c1, c2);
+end ConnectExternalObject1;
+
+// Result:
+// function ExtObj.constructor
+//   output ExtObj obj;
+//
+//   external "C" obj = initObject();
+// end ExtObj.constructor;
+//
+// function ExtObj.destructor
+//   input ExtObj obj;
+//
+//   external "C" destroyObject(obj);
+// end ExtObj.destructor;
+//
+// class ConnectExternalObject1
+//   ExtObj c1.eo;
+//   ExtObj c2.eo;
+// equation
+//   c1.eo = c2.eo;
+// end ConnectExternalObject1;
+// endResult

flattening/modelica/scodeinst/Makefile

@@ -219,6 +219,7 @@ ConnectComplex1.mo \
 ConnectComplexFlow1.mo \
 ConnectDiffOrder1.mo \
 ConnectDiffOrder2.mo \
+ConnectExternalObject1.mo \
 ConnectInitial.mo \
 ConnectInvalidForm1.mo \
 ConnectInvalidType1.mo \