[NF] Add test for duplicate params in function.

Belonging to [master]:
  - OpenModelica/OMCompiler#2410
  - OpenModelica/OpenModelica-testsuite#937

flattening/modelica/scodeinst/FuncDuplicateParams1.mo

@@ -0,0 +1,34 @@
+// name: FuncDuplicateParams1
+// keywords:
+// status: correct
+// cflags: -d=newInst
+//
+// Checks that duplicate elements are handled correctly in functions.
+//
+
+function f1
+  input Real x;
+  output Real y;
+end f1;
+
+function f2
+  input Real x;
+  output Real y;
+end f2;
+
+function f
+  extends f1;
+  extends f2;
+algorithm
+  y := x; 
+end f;
+
+model FuncDuplicateParams1
+  constant Real x = f(1.0);
+end FuncDuplicateParams1;
+
+// Result:
+// class FuncDuplicateParams1
+//   constant Real x = 1.0;
+// end FuncDuplicateParams1;
+// endResult

flattening/modelica/scodeinst/Makefile

@@ -380,6 +380,7 @@ FuncBuiltinVectorWrongType1.mo \
 FuncBuiltinZeros.mo \
 FuncClassParam.mo \
 FuncDefaultArg1.mo \
+FuncDuplicateParams1.mo \
 FuncExtends.mo \
 FuncInnerParam.mo \
 FuncInteger.mo \