Do not parse closures when allow_anonymous_fn is false.

RELEASES.md

@@ -7,6 +7,15 @@ Version 0.19.0
 Bug fixes
 ---------
 
+* `Engine::compile_expression`, `Engine::eval_expression` etc. no longer parse anonymous functions and closures.
+
+
+Version 0.18.2
+==============
+
+Bug fixes
+---------
+
 * Fixes bug that prevents calling functions in closures.
 * Fixes bug that erroneously consumes the first argument to a module-qualified function call.
 

doc/src/engine/expressions.md

@@ -11,9 +11,11 @@ In these cases, use the `Engine::compile_expression` and `Engine::eval_expressio
 let result = engine.eval_expression::<i64>("2 + (10 + 10) * 2")?;
 ```
 
-When evaluating _expressions_, no full-blown statement (e.g. `if`, `while`, `for`) - not even variable assignment -
+When evaluating _expressions_, no full-blown statement (e.g. `if`, `while`, `for`, `fn`) - not even variable assignment -
 is supported and will be considered parse errors when encountered.
 
+[Closures] and [anonymous functions] are also not supported because in the background they compile to functions.
+
 ```rust
 // The following are all syntax errors because the script is not an expression.
 

src/parser.rs

@@ -1862,7 +1862,7 @@ fn parse_unary(
         }
         // | ...
         #[cfg(not(feature = "no_function"))]
-        Token::Pipe | Token::Or => {
+        Token::Pipe | Token::Or if settings.allow_anonymous_fn => {
             let mut new_state = ParseState::new(
                 state.engine,
                 #[cfg(not(feature = "unchecked"))]
@@ -3353,6 +3353,8 @@ impl Engine {
         };
         let expr = parse_expr(input, &mut state, &mut functions, settings)?;
 
+        assert!(functions.is_empty());
+
         match input.peek().unwrap() {
             (Token::EOF, _) => (),
             // Return error if the expression doesn't end

tests/closures.rs

@@ -1,7 +1,11 @@
 #![cfg(not(feature = "no_function"))]
-use rhai::{Dynamic, Engine, EvalAltResult, FnPtr, Module, RegisterFn, INT};
+use rhai::{
+    Dynamic, Engine, EvalAltResult, FnPtr, Map, Module, ParseErrorType, RegisterFn, Scope, INT,
+};
 use std::any::TypeId;
+use std::cell::RefCell;
 use std::mem::take;
+use std::rc::Rc;
 
 #[test]
 fn test_fn_ptr_curry_call() -> Result<(), Box<EvalAltResult>> {
@@ -39,6 +43,14 @@ fn test_fn_ptr_curry_call() -> Result<(), Box<EvalAltResult>> {
 fn test_closures() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
 
+    assert!(matches!(
+        *engine
+            .compile_expression("let f = |x| {};")
+            .expect_err("should error")
+            .0,
+        ParseErrorType::BadInput(_)
+    ));
+
     assert_eq!(
         engine.eval::<INT>(
             r#"
@@ -181,3 +193,59 @@ fn test_closures_data_race() -> Result<(), Box<EvalAltResult>> {
 
     Ok(())
 }
+
+type MyType = Rc<RefCell<INT>>;
+
+#[test]
+#[cfg(not(feature = "no_object"))]
+#[cfg(not(feature = "sync"))]
+fn test_closure_shared_obj() -> Result<(), Box<EvalAltResult>> {
+    let mut engine = Engine::new();
+
+    // Register API on MyType
+    engine
+        .register_type_with_name::<MyType>("MyType")
+        .register_get_set(
+            "data",
+            |p: &mut MyType| *p.borrow(),
+            |p: &mut MyType, value: INT| *p.borrow_mut() = value,
+        )
+        .register_fn("+=", |p1: &mut MyType, p2: MyType| {
+            *p1.borrow_mut() += *p2.borrow()
+        })
+        .register_fn("-=", |p1: &mut MyType, p2: MyType| {
+            *p1.borrow_mut() -= *p2.borrow()
+        });
+
+    let engine = engine; // Make engine immutable
+
+    let code = r#"
+        #{
+            name: "A",
+            description: "B",
+            cost: 1,
+            health_added: 0,
+            action: |p1, p2| { p1 += p2 }
+        }
+    "#;
+
+    let ast = engine.compile(code)?;
+    let res = engine.eval_ast::<Map>(&ast)?;
+
+    // Make closure
+    let f = move |p1: MyType, p2: MyType| -> Result<(), Box<EvalAltResult>> {
+        let action_ptr = res["action"].clone().cast::<FnPtr>();
+        let name = action_ptr.fn_name();
+        engine.call_fn::<_, ()>(&mut Scope::new(), &ast, name, (p1, p2))
+    };
+
+    // Test closure
+    let p1 = Rc::new(RefCell::new(41));
+    let p2 = Rc::new(RefCell::new(1));
+
+    f(p1.clone(), p2.clone())?;
+
+    assert_eq!(*p1.borrow(), 42);
+
+    Ok(())
+}