Fix bugs in function signature type checking.

Bug: issue #992
Test: new test cases

compiler/expressions.cpp

@@ -337,6 +337,9 @@ static bool funcarg_compare(QualType formal, QualType actual) {
         }
     }
 
+    if (formal_type->isReference() != actual_type->isReference())
+        return false;
+
     if (!matchtag(formal_type, actual_type, MATCHTAG_SILENT | MATCHTAG_FUNCARG))
         return false;
     return true;

tests/compile-only/fail-ref-compare-function-signature.sp

@@ -0,0 +1,29 @@
+typedef CallbackCell = function void (any value);
+typedef CallbackRef = function void (any &value);
+
+public void OnPluginStart()
+{
+	// 4 tests below does report error in 1.11
+
+	CallbackCell badcellany = RefAny;	// no error
+	ReturnFunction(badcellany);
+
+	CallbackCell badcellint = RefInt;	// no error
+	ReturnFunction(badcellint);
+
+	CallbackRef badrefany = CellAny;	// no error
+	ReturnFunction(badrefany);
+
+	CallbackRef badrefint = CellInt;	// error
+	ReturnFunction(badrefint);
+}
+
+void CellAny(any value) {}
+void CellInt(int value) {}
+void RefAny(any &value) {}
+void RefInt(int &value) {}
+
+Function ReturnFunction(Function func)
+{
+	return func;
+}

tests/compile-only/fail-ref-compare-function-signature.txt

@@ -0,0 +1,4 @@
+(8) : error 100: function prototypes do not match
+(11) : error 100: function prototypes do not match
+(14) : error 100: function prototypes do not match
+(17) : error 100: function prototypes do not match