--- a/absyntax/absyntax.def	Fri Feb 10 19:04:31 2012 +0000
+++ b/absyntax/absyntax.def	Mon Feb 13 13:45:57 2012 +0000
@@ -938,7 +938,8 @@
  * | il_call_operator prev_declared_fb_name '(' il_operand_list ')'
  * | il_call_operator prev_declared_fb_name '(' eol_list il_param_list ')'
  */
-SYM_REF4(il_fb_call_c, il_call_operator, fb_name, il_operand_list, il_param_list)
+/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
+SYM_REF4(il_fb_call_c, il_call_operator, fb_name, il_operand_list, il_param_list, symbol_c *called_fb_declaration;)
 
 
 /* | function_name '(' eol_list [il_param_list] ')' */
@@ -1099,14 +1100,7 @@
 /* fb_name '(' [param_assignment_list] ')' */
 /*    formal_param_list -> may be NULL ! */
 /* nonformal_param_list -> may be NULL ! */
-/* NOTES:
- *    The parameter 'called_fb_declaration'... 
- *       ...is used to pass data between two passes of stage 3.
- *       (actually set in fill_candidate_datatypes_c, and used in narrow_candidate_datatypes_c and print_datatypes_error_c).
- *       This allows fill_candidate_datatypes_c to figure out whether it is a valid FB call,
- *       and let the other classes handle it aproproately.
- *       It could also be used in stage 4, if required.
- */
+/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
 SYM_REF3(fb_invocation_c, fb_name, formal_param_list, nonformal_param_list, symbol_c *called_fb_declaration;)
 
 /* helper symbol for fb_invocation */

--- a/stage3/fill_candidate_datatypes.cc	Fri Feb 10 19:04:31 2012 +0000
+++ b/stage3/fill_candidate_datatypes.cc	Mon Feb 13 13:45:57 2012 +0000
@@ -841,8 +841,40 @@
   return NULL;
 }
 
+
+/*   il_call_operator prev_declared_fb_name
+ * | il_call_operator prev_declared_fb_name '(' ')'
+ * | il_call_operator prev_declared_fb_name '(' eol_list ')'
+ * | il_call_operator prev_declared_fb_name '(' il_operand_list ')'
+ * | il_call_operator prev_declared_fb_name '(' eol_list il_param_list ')'
+ */
+/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
+// SYM_REF4(il_fb_call_c, il_call_operator, fb_name, il_operand_list, il_param_list, symbol_c *called_fb_declaration)
 void *fill_candidate_datatypes_c::visit(il_fb_call_c *symbol) {
-}
+	bool compatible = false;
+	symbol_c *fb_decl = search_varfb_instance_type->get_basetype_decl(symbol->fb_name);
+	/* Although a call to a non-declared FB is a semantic error, this is currently caught by stage 2! */
+	if (NULL == fb_decl) ERROR;
+
+	if (symbol->  il_param_list != NULL) {
+		symbol->il_param_list->accept(*this);
+		compatible = match_formal_call(symbol, fb_decl);
+	}
+	if (symbol->il_operand_list != NULL) {
+		symbol->il_operand_list->accept(*this);
+		compatible = match_nonformal_call(symbol, fb_decl);
+	}
+
+	/* The print_datatypes_error_c does not rely on this called_fb_declaration pointer being != NULL to conclude that
+	 * we have a datat type incompatibility error, so setting it to the correct fb_decl is actually safe,
+	 * as the compiler will never reach the compilation stage!
+	 */
+	symbol->called_fb_declaration = fb_decl;
+
+	if (debug) std::cout << "FB [] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	return NULL;
+}
+
 
 /* | function_name '(' eol_list [il_param_list] ')' */
 /* NOTE: The parameter 'called_function_declaration' is used to pass data between the stage 3 and stage 4. */

--- a/stage3/narrow_candidate_datatypes.cc	Fri Feb 10 19:04:31 2012 +0000
+++ b/stage3/narrow_candidate_datatypes.cc	Mon Feb 13 13:45:57 2012 +0000
@@ -414,9 +414,39 @@
 return NULL;
 }
 
+/*   il_call_operator prev_declared_fb_name
+ * | il_call_operator prev_declared_fb_name '(' ')'
+ * | il_call_operator prev_declared_fb_name '(' eol_list ')'
+ * | il_call_operator prev_declared_fb_name '(' il_operand_list ')'
+ * | il_call_operator prev_declared_fb_name '(' eol_list il_param_list ')'
+ */
+/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
+// SYM_REF4(il_fb_call_c, il_call_operator, fb_name, il_operand_list, il_param_list, symbol_c *called_fb_declaration)
 void *narrow_candidate_datatypes_c::visit(il_fb_call_c *symbol) {
-	return NULL;
-}
+	/* Note: We do not use the symbol->called_fb_declaration value (set in fill_candidate_datatypes_c)
+	 *       because we try to identify any other datatype errors in the expressions used in the 
+	 *       parameters to the FB call. e.g.
+	 *          fb_var( 
+	 *             in1 := var1,
+	 *             in2 := (
+	 *                       LD 56
+	 *                       ADD 43
+	 *                    )
+	 *             )
+	 *       even it the call to the FB is invalid. 
+	 *       This makes sense because it may be errors in those expressions which are
+	 *       making this an invalid call, so it makes sense to point them out to the user!
+	 */
+	symbol_c *fb_decl = search_varfb_instance_type->get_basetype_decl(symbol->fb_name);
+
+	/* Although a call to a non-declared FB is a semantic error, this is currently caught by stage 2! */
+	if (NULL == fb_decl) ERROR;
+	if (NULL != symbol->il_operand_list)  narrow_nonformal_call(symbol, fb_decl);
+	if (NULL != symbol->  il_param_list)     narrow_formal_call(symbol, fb_decl);
+
+	return NULL;
+}
+
 
 /* | function_name '(' eol_list [il_param_list] ')' */
 /* NOTE: The parameter 'called_function_declaration' is used to pass data between the stage 3 and stage 4. */

--- a/stage3/print_datatypes_error.cc	Fri Feb 10 19:04:31 2012 +0000
+++ b/stage3/print_datatypes_error.cc	Mon Feb 13 13:45:57 2012 +0000
@@ -1140,14 +1140,7 @@
 /* fb_name '(' [param_assignment_list] ')' */
 /*    formal_param_list -> may be NULL ! */
 /* nonformal_param_list -> may be NULL ! */
-/* NOTES:
- *    The parameter 'called_fb_declaration'... 
- *       ...is used to pass data between two passes of stage 3.
- *       (actually set in fill_candidate_datatypes_c, and used in narrow_candidate_datatypes_c and print_datatypes_error_c).
- *       This allows fill_candidate_datatypes_c to figure out whether it is a valid FB call,
- *       and let the other classes handle it aproproately.
- *       It could also be used in stage 4, if required.
- */
+/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
 // SYM_REF3(fb_invocation_c, fb_name, formal_param_list, nonformal_param_list, symbol_c *called_fb_declaration;)
 void *print_datatypes_error_c::visit(fb_invocation_c *symbol) {
 	symbol_c *param_value, *param_name;