Implement closure functions (#1442)

boa/examples/closures.rs

@@ -0,0 +1,20 @@
+use boa::{Context, JsString, Value};
+
+fn main() -> Result<(), Value> {
+    let mut context = Context::new();
+
+    let variable = JsString::new("I am a captured variable");
+
+    // We register a global closure function that has the name 'closure' with length 0.
+    context.register_global_closure("closure", 0, move |_, _, _| {
+        // This value is captured from main function.
+        Ok(variable.clone().into())
+    })?;
+
+    assert_eq!(
+        context.eval("closure()")?,
+        "I am a captured variable".into()
+    );
+
+    Ok(())
+}

boa/src/builtins/array/mod.rs

@@ -45,16 +45,14 @@ impl BuiltIn for Array {
 
         let symbol_iterator = WellKnownSymbols::iterator();
 
-        let get_species = FunctionBuilder::new(context, Self::get_species)
+        let get_species = FunctionBuilder::native(context, Self::get_species)
             .name("get [Symbol.species]")
             .constructable(false)
-            .callable(true)
             .build();
 
-        let values_function = FunctionBuilder::new(context, Self::values)
+        let values_function = FunctionBuilder::native(context, Self::values)
             .name("values")
             .length(0)
-            .callable(true)
             .constructable(false)
             .build();
 
@@ -166,7 +164,7 @@ impl Array {
                 // i. Let intLen be ! ToUint32(len).
                 let int_len = len.to_u32(context).unwrap();
                 // ii. If SameValueZero(intLen, len) is false, throw a RangeError exception.
-                if !Value::same_value_zero(&int_len.into(), &len) {
+                if !Value::same_value_zero(&int_len.into(), len) {
                     return Err(context.construct_range_error("invalid array length"));
                 }
                 int_len

boa/src/builtins/function/mod.rs

@@ -15,21 +15,25 @@ use crate::object::PROTOTYPE;
 use crate::{
     builtins::{Array, BuiltIn},
     environment::lexical_environment::Environment,
-    gc::{empty_trace, Finalize, Trace},
+    gc::{custom_trace, empty_trace, Finalize, Trace},
     object::{ConstructorBuilder, FunctionBuilder, GcObject, Object, ObjectData},
     property::{Attribute, DataDescriptor},
     syntax::ast::node::{FormalParameter, RcStatementList},
     BoaProfiler, Context, Result, Value,
 };
 use bitflags::bitflags;
 use std::fmt::{self, Debug};
+use std::rc::Rc;
 
 #[cfg(test)]
 mod tests;
 
-/// _fn(this, arguments, context) -> ResultValue_ - The signature of a built-in function
+/// _fn(this, arguments, context) -> ResultValue_ - The signature of a native built-in function
 pub type NativeFunction = fn(&Value, &[Value], &mut Context) -> Result<Value>;
 
+/// _fn(this, arguments, context) -> ResultValue_ - The signature of a closure built-in function
+pub type ClosureFunction = dyn Fn(&Value, &[Value], &mut Context) -> Result<Value>;
+
 #[derive(Clone, Copy, Finalize)]
 pub struct BuiltInFunction(pub(crate) NativeFunction);
 
@@ -52,31 +56,12 @@ impl Debug for BuiltInFunction {
 bitflags! {
     #[derive(Finalize, Default)]
     pub struct FunctionFlags: u8 {
-        const CALLABLE = 0b0000_0001;
         const CONSTRUCTABLE = 0b0000_0010;
         const LEXICAL_THIS_MODE = 0b0000_0100;
     }
 }
 
 impl FunctionFlags {
-    pub(crate) fn from_parameters(callable: bool, constructable: bool) -> Self {
-        let mut flags = Self::default();
-
-        if callable {
-            flags |= Self::CALLABLE;
-        }
-        if constructable {
-            flags |= Self::CONSTRUCTABLE;
-        }
-
-        flags
-    }
-
-    #[inline]
-    pub(crate) fn is_callable(&self) -> bool {
-        self.contains(Self::CALLABLE)
-    }
-
     #[inline]
     pub(crate) fn is_constructable(&self) -> bool {
         self.contains(Self::CONSTRUCTABLE)
@@ -97,9 +82,16 @@ unsafe impl Trace for FunctionFlags {
 /// FunctionBody is specific to this interpreter, it will either be Rust code or JavaScript code (AST Node)
 ///
 /// <https://tc39.es/ecma262/#sec-ecmascript-function-objects>
-#[derive(Debug, Clone, Finalize, Trace)]
+#[derive(Finalize)]
 pub enum Function {
-    BuiltIn(BuiltInFunction, FunctionFlags),
+    Native {
+        function: BuiltInFunction,
+        constructable: bool,
+    },
+    Closure {
+        function: Rc<ClosureFunction>,
+        constructable: bool,
+    },
     Ordinary {
         flags: FunctionFlags,
         body: RcStatementList,
@@ -108,6 +100,24 @@ pub enum Function {
     },
 }
 
+impl Debug for Function {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Function {{ ... }}")
+    }
+}
+
+unsafe impl Trace for Function {
+    custom_trace!(this, {
+        match this {
+            Function::Native { .. } => {}
+            Function::Closure { .. } => {}
+            Function::Ordinary { environment, .. } => {
+                mark(environment);
+            }
+        }
+    });
+}
+
 impl Function {
     // Adds the final rest parameters to the Environment as an array
     pub(crate) fn add_rest_param(
@@ -154,18 +164,11 @@ impl Function {
             .expect("Failed to intialize binding");
     }
 
-    /// Returns true if the function object is callable.
-    pub fn is_callable(&self) -> bool {
-        match self {
-            Self::BuiltIn(_, flags) => flags.is_callable(),
-            Self::Ordinary { flags, .. } => flags.is_callable(),
-        }
-    }
-
     /// Returns true if the function object is constructable.
     pub fn is_constructable(&self) -> bool {
         match self {
-            Self::BuiltIn(_, flags) => flags.is_constructable(),
+            Self::Native { constructable, .. } => *constructable,
+            Self::Closure { constructable, .. } => *constructable,
             Self::Ordinary { flags, .. } => flags.is_constructable(),
         }
     }
@@ -230,7 +233,10 @@ pub fn make_builtin_fn<N>(
     let _timer = BoaProfiler::global().start_event(&format!("make_builtin_fn: {}", &name), "init");
 
     let mut function = Object::function(
-        Function::BuiltIn(function.into(), FunctionFlags::CALLABLE),
+        Function::Native {
+            function: function.into(),
+            constructable: false,
+        },
         interpreter
             .standard_objects()
             .function_object()
@@ -270,10 +276,10 @@ impl BuiltInFunctionObject {
             .expect("this should be an object")
             .set_prototype_instance(prototype.into());
 
-        this.set_data(ObjectData::Function(Function::BuiltIn(
-            BuiltInFunction(|_, _, _| Ok(Value::undefined())),
-            FunctionFlags::CALLABLE | FunctionFlags::CONSTRUCTABLE,
-        )));
+        this.set_data(ObjectData::Function(Function::Native {
+            function: BuiltInFunction(|_, _, _| Ok(Value::undefined())),
+            constructable: true,
+        }));
         Ok(this)
     }
 
@@ -342,10 +348,9 @@ impl BuiltIn for BuiltInFunctionObject {
         let _timer = BoaProfiler::global().start_event("function", "init");
 
         let function_prototype = context.standard_objects().function_object().prototype();
-        FunctionBuilder::new(context, Self::prototype)
+        FunctionBuilder::native(context, Self::prototype)
             .name("")
             .length(0)
-            .callable(true)
             .constructable(false)
             .build_function_prototype(&function_prototype);
 

boa/src/builtins/map/mod.rs

@@ -46,16 +46,14 @@ impl BuiltIn for Map {
         let to_string_tag = WellKnownSymbols::to_string_tag();
         let iterator_symbol = WellKnownSymbols::iterator();
 
-        let get_species = FunctionBuilder::new(context, Self::get_species)
+        let get_species = FunctionBuilder::native(context, Self::get_species)
             .name("get [Symbol.species]")
             .constructable(false)
-            .callable(true)
             .build();
 
-        let entries_function = FunctionBuilder::new(context, Self::entries)
+        let entries_function = FunctionBuilder::native(context, Self::entries)
             .name("entries")
             .length(0)
-            .callable(true)
             .constructable(false)
             .build();
 

boa/src/builtins/object/mod.rs

@@ -360,7 +360,7 @@ impl Object {
     /// Define a property in an object
     pub fn define_property(_: &Value, args: &[Value], context: &mut Context) -> Result<Value> {
         let object = args.get(0).cloned().unwrap_or_else(Value::undefined);
-        if let Some(mut object) = object.as_object() {
+        if let Some(object) = object.as_object() {
             let key = args
                 .get(1)
                 .unwrap_or(&Value::undefined())

boa/src/builtins/regexp/mod.rs

@@ -75,53 +75,44 @@ impl BuiltIn for RegExp {
     fn init(context: &mut Context) -> (&'static str, Value, Attribute) {
         let _timer = BoaProfiler::global().start_event(Self::NAME, "init");
 
-        let get_species = FunctionBuilder::new(context, Self::get_species)
+        let get_species = FunctionBuilder::native(context, Self::get_species)
             .name("get [Symbol.species]")
             .constructable(false)
-            .callable(true)
             .build();
 
         let flag_attributes = Attribute::CONFIGURABLE | Attribute::NON_ENUMERABLE;
 
-        let get_global = FunctionBuilder::new(context, Self::get_global)
+        let get_global = FunctionBuilder::native(context, Self::get_global)
             .name("get global")
             .constructable(false)
-            .callable(true)
             .build();
-        let get_ignore_case = FunctionBuilder::new(context, Self::get_ignore_case)
+        let get_ignore_case = FunctionBuilder::native(context, Self::get_ignore_case)
             .name("get ignoreCase")
             .constructable(false)
-            .callable(true)
             .build();
-        let get_multiline = FunctionBuilder::new(context, Self::get_multiline)
+        let get_multiline = FunctionBuilder::native(context, Self::get_multiline)
             .name("get multiline")
             .constructable(false)
-            .callable(true)
             .build();
-        let get_dot_all = FunctionBuilder::new(context, Self::get_dot_all)
+        let get_dot_all = FunctionBuilder::native(context, Self::get_dot_all)
             .name("get dotAll")
             .constructable(false)
-            .callable(true)
             .build();
-        let get_unicode = FunctionBuilder::new(context, Self::get_unicode)
+        let get_unicode = FunctionBuilder::native(context, Self::get_unicode)
             .name("get unicode")
             .constructable(false)
-            .callable(true)
             .build();
-        let get_sticky = FunctionBuilder::new(context, Self::get_sticky)
+        let get_sticky = FunctionBuilder::native(context, Self::get_sticky)
             .name("get sticky")
             .constructable(false)
-            .callable(true)
             .build();
-        let get_flags = FunctionBuilder::new(context, Self::get_flags)
+        let get_flags = FunctionBuilder::native(context, Self::get_flags)
             .name("get flags")
             .constructable(false)
-            .callable(true)
             .build();
-        let get_source = FunctionBuilder::new(context, Self::get_source)
+        let get_source = FunctionBuilder::native(context, Self::get_source)
             .name("get source")
             .constructable(false)
-            .callable(true)
             .build();
         let regexp_object = ConstructorBuilder::with_standard_object(
             context,

boa/src/builtins/set/mod.rs

@@ -39,14 +39,12 @@ impl BuiltIn for Set {
     fn init(context: &mut Context) -> (&'static str, Value, Attribute) {
         let _timer = BoaProfiler::global().start_event(Self::NAME, "init");
 
-        let get_species = FunctionBuilder::new(context, Self::get_species)
+        let get_species = FunctionBuilder::native(context, Self::get_species)
             .name("get [Symbol.species]")
             .constructable(false)
-            .callable(true)
             .build();
 
-        let size_getter = FunctionBuilder::new(context, Self::size_getter)
-            .callable(true)
+        let size_getter = FunctionBuilder::native(context, Self::size_getter)
             .constructable(false)
             .name("get size")
             .build();
@@ -55,10 +53,9 @@ impl BuiltIn for Set {
 
         let to_string_tag = WellKnownSymbols::to_string_tag();
 
-        let values_function = FunctionBuilder::new(context, Self::values)
+        let values_function = FunctionBuilder::native(context, Self::values)
             .name("values")
             .length(0)
-            .callable(true)
             .constructable(false)
             .build();
 

boa/src/builtins/symbol/mod.rs

@@ -97,10 +97,9 @@ impl BuiltIn for Symbol {
 
         let attribute = Attribute::READONLY | Attribute::NON_ENUMERABLE | Attribute::PERMANENT;
 
-        let get_description = FunctionBuilder::new(context, Self::get_description)
+        let get_description = FunctionBuilder::native(context, Self::get_description)
             .name("get description")
             .constructable(false)
-            .callable(true)
             .build();
 
         let symbol_object = ConstructorBuilder::with_standard_object(