Replace leftover string with the proper type in C# set typemap

This is just a mistake remaining from generalizing the old
string-specific typemap to any type.

Fix it now and update a unit test to test for sets of objects other than
strings.

Examples/test-suite/csharp/li_std_set_runme.cs

@@ -85,5 +85,12 @@ public class runme
         ss = new StringSet{"foo", "bar", "baz"};
         ss.UnionWith(new[] {"baz", "quux"});
         checkThat(ss.SetEquals(new[] {"foo", "bar", "baz", "quux"}), "UnionWith works");
+
+        // Check a set of another type.
+        FooSet fooSet = new FooSet();
+        ISet<Foo> fooISet = fooSet;
+        checkThat(fooISet.Count == 0, "is initially empty");
+        checkThat(fooISet.Add(new Foo(17)), "added successfully");
+        checkThat(fooISet.Count == 1, "is not empty any more");
     }
 }

Examples/test-suite/java/li_std_set_runme.java

@@ -71,5 +71,11 @@ public class li_std_set_runme {
     checkThat(ss.removeAll(found));
     checkThat(ss.isEmpty());
     checkThat(ss.size() == 0);
+
+    // Check a set of another type.
+    java.util.AbstractSet<Foo> fooSet = new FooSet();
+    checkThat(fooSet.isEmpty());
+    checkThat(fooSet.add(new Foo(17)));
+    checkThat(fooSet.size() == 1);
   }
 }

Examples/test-suite/li_std_set.i

@@ -23,7 +23,25 @@
     %template(v_int) std::vector<int>;
     %template(set_string) std::set<std::string>;
 #elif defined(SWIGJAVA) || defined(SWIGCSHARP)
+    // This operator is only defined because it's needed to store objects of
+    // type Foo in std::set in C++, we don't need to wrap it.
+    %ignore operator<;
+    %inline %{
+        struct Foo
+        {
+            explicit Foo(int n) : n(n) {}
+
+            int n;
+
+            friend bool operator<(Foo foo1, Foo foo2)
+            {
+                return foo1.n < foo2.n;
+            }
+        };
+    %}
+
     %template(StringSet) std::set<std::string>;
+    %template(FooSet) std::set<Foo>;
 #endif
 
 #if defined(SWIGRUBY)

Lib/csharp/std_set.i

@@ -30,7 +30,7 @@ class set {
 
 %typemap(csinterfaces) std::set<T> "global::System.IDisposable, global::System.Collections.Generic.ISet<$typemap(cstype, T)>\n";
 %proxycode %{
-  void global::System.Collections.Generic.ICollection<$typemap(cstype, T)>.Add(string item) {
+  void global::System.Collections.Generic.ICollection<$typemap(cstype, T)>.Add($typemap(cstype, T) item) {
       ((global::System.Collections.Generic.ISet<$typemap(cstype, T)>)this).Add(item);
   }