Fix bug with wrong method call hash.

tests/functions.rs

@@ -0,0 +1,25 @@
+#![cfg(not(feature = "no_function"))]
+use rhai::{Engine, EvalAltResult, Func, ParseErrorType, Scope, INT};
+
+#[test]
+fn test_functions() -> Result<(), Box<EvalAltResult>> {
+    let engine = Engine::new();
+
+    assert_eq!(engine.eval::<i64>("fn add(x, n) { x + n } add(40, 2)")?, 42);
+
+    #[cfg(not(feature = "no_object"))]
+    assert_eq!(
+        engine.eval::<i64>("fn add(x, n) { x + n } let x = 40; x.add(2)")?,
+        42
+    );
+
+    assert_eq!(engine.eval::<i64>("fn mul2(x) { x * 2 } mul2(21)")?, 42);
+
+    #[cfg(not(feature = "no_object"))]
+    assert_eq!(
+        engine.eval::<i64>("fn mul2(x) { x * 2 } let x = 21; x.mul2()")?,
+        42
+    );
+
+    Ok(())
+}