Allow binding of this pointer in FnPtr calls.

tests/call_fn.rs

@@ -116,7 +116,7 @@ fn test_anonymous_fn() -> Result<(), Box<EvalAltResult>> {
 
 #[test]
 #[cfg(not(feature = "no_object"))]
-fn test_fn_ptr() -> Result<(), Box<EvalAltResult>> {
+fn test_fn_ptr_raw() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
 
     engine.register_raw_fn(

tests/fn_ptr.rs

@@ -0,0 +1,80 @@
+use rhai::{Engine, EvalAltResult, RegisterFn, INT};
+
+#[test]
+fn test_fn_ptr() -> Result<(), Box<EvalAltResult>> {
+    let mut engine = Engine::new();
+
+    engine.register_fn("bar", |x: &mut INT, y: INT| *x += y);
+
+    #[cfg(not(feature = "no_object"))]
+    assert_eq!(
+        engine.eval::<INT>(
+            r#"
+                let f = Fn("bar");
+                let x = 40;
+                f.call(x, 2);
+                x
+            "#
+        )?,
+        40
+    );
+
+    #[cfg(not(feature = "no_object"))]
+    assert_eq!(
+        engine.eval::<INT>(
+            r#"
+                let f = Fn("bar");
+                let x = 40;
+                x.call(f, 2);
+                x
+            "#
+        )?,
+        42
+    );
+
+    assert_eq!(
+        engine.eval::<INT>(
+            r#"
+                let f = Fn("bar");
+                let x = 40;
+                call(f, x, 2);
+                x
+            "#
+        )?,
+        42
+    );
+
+    #[cfg(not(feature = "no_function"))]
+    #[cfg(not(feature = "no_object"))]
+    assert_eq!(
+        engine.eval::<INT>(
+            r#"
+                fn foo(x) { this += x; }
+
+                let f = Fn("foo");
+                let x = 40;
+                x.call(f, 2);
+                x
+            "#
+        )?,
+        42
+    );
+
+    #[cfg(not(feature = "no_function"))]
+    assert!(matches!(
+        *engine
+            .eval::<INT>(
+                r#"
+                fn foo(x) { this += x; }
+
+                let f = Fn("foo");
+                call(f, 2);
+                x
+            "#
+            )
+            .expect_err("should error"),
+        EvalAltResult::ErrorInFunctionCall(fn_name, err, _) if fn_name == "foo" && matches!(*err, EvalAltResult::ErrorUnboundedThis(_))
+    ));
+
+    Ok(())
+}