toString() for FunctionN classes

It's implemented as if the types were reified: getting the real type parameters
of the corresponding FunctionN class

generators/org/jetbrains/jet/generators/runtime/GenerateFunctions.java

@@ -123,10 +123,17 @@ public class GenerateFunctions {
         out.print(" implements " + kind.getClassName(i));
         generateTypeParameters(out, i, kind);
         out.println(" {");
-        // TODO: toString()
+        generateToStringForFunctionImpl(out);
         out.println("}");
     }
 
+    private static void generateToStringForFunctionImpl(PrintStream out) {
+        out.println("    @Override");
+        out.println("    public String toString() {");
+        out.println("        return getClass().getGenericSuperclass().toString();");
+        out.println("    }");
+    }
+
     private static void generateRuntimeClassHeader(PrintStream out) {
         try {
             out.println(FileUtil.loadFile(new File("injector-generator/copyright.txt")));