From 821632972b352d487bb052770cf47c40104151b5 Mon Sep 17 00:00:00 2001
From: Jason Williams <936006+jasonwilliams@users.noreply.github.com>
Date: Wed, 25 Sep 2019 15:32:33 +0100
Subject: [PATCH] Addition of arguments object (#109)

* testing PR

* making a start to arguments object

* arguments

* finishing arguments for now
---
 benches/fib.rs         |  2 --
 src/lib/exec.rs        | 14 +++++++++---
 src/lib/js/function.rs | 50 ++++++++++++++++++++++++++++++++++++++++++
 tests/js/test.js       |  6 +++--
 4 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/benches/fib.rs b/benches/fib.rs
index 1ef30fbdec..09af95c222 100644
--- a/benches/fib.rs
+++ b/benches/fib.rs
@@ -2,8 +2,6 @@
 extern crate criterion;
 
 use boa::exec;
-use boa::syntax::lexer::Lexer;
-use boa::syntax::parser::Parser;
 use criterion::black_box;
 use criterion::Criterion;
 
diff --git a/src/lib/exec.rs b/src/lib/exec.rs
index 5e4881d681..19458ce4f6 100644
--- a/src/lib/exec.rs
+++ b/src/lib/exec.rs
@@ -2,7 +2,7 @@ use crate::{
     environment::lexical_environment::{new_function_environment, LexicalEnvironment},
     js::{
         array, boolean, console, function,
-        function::{Function, RegularFunction},
+        function::{create_unmapped_arguments_object, Function, RegularFunction},
         json, math, object,
         object::{ObjectKind, INSTANCE_PROTOTYPE, PROTOTYPE},
         regexp, string,
@@ -487,10 +487,18 @@ impl Interpreter {
                     ));
                     for i in 0..data.args.len() {
                         let name = data.args.get(i).unwrap();
-                        let expr = arguments_list.get(i).unwrap();
+                        let expr: &Value = arguments_list.get(i).unwrap();
                         self.environment.create_mutable_binding(name.clone(), false);
-                        self.environment.initialize_binding(name, expr.to_owned());
+                        self.environment.initialize_binding(name, expr.clone());
                     }
+
+                    // Add arguments object
+                    let arguments_obj = create_unmapped_arguments_object(arguments_list);
+                    self.environment
+                        .create_mutable_binding("arguments".to_string(), false);
+                    self.environment
+                        .initialize_binding("arguments", arguments_obj);
+
                     let result = self.run(&data.expr);
                     self.environment.pop();
                     result
diff --git a/src/lib/js/function.rs b/src/lib/js/function.rs
index 7737488530..06d219d9ad 100644
--- a/src/lib/js/function.rs
+++ b/src/lib/js/function.rs
@@ -101,3 +101,53 @@ pub fn init(global: &Value) {
     let global_ptr = global;
     global_ptr.set_field_slice("Function", _create());
 }
+
+/// Arguments
+/// https://tc39.es/ecma262/#sec-createunmappedargumentsobject
+pub fn create_unmapped_arguments_object(arguments_list: Vec<Value>) -> Value {
+    let len = arguments_list.len();
+    let mut obj = Object::default();
+    obj.set_internal_slot("ParameterMap", Gc::new(ValueData::Undefined));
+    // Set length
+    let mut length = Property::default();
+    length = length.writable(true).value(to_value(len));
+    // Define length as a property
+    obj.define_own_property("length".to_string(), length);
+    let mut index: usize = 0;
+    while index < len {
+        let val = arguments_list.get(index).unwrap();
+        let mut prop = Property::default();
+        prop = prop
+            .value(val.clone())
+            .enumerable(true)
+            .writable(true)
+            .configurable(true);
+
+        obj.properties.insert(index.to_string(), prop);
+        index += 1;
+    }
+
+    to_value(obj)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::exec::Executor;
+    use crate::{forward, forward_val, js::value::from_value};
+
+    #[test]
+    fn check_arguments_object() {
+        let mut engine = Executor::new();
+        let init = r#"
+        function jason(a, b) {
+            return arguments[0];
+        }
+        const val = jason(100, 6);
+        "#;
+
+        forward(&mut engine, init);
+        let return_val = forward_val(&mut engine, "val").expect("value expected");
+        assert_eq!(return_val.is_double(), true);
+        assert_eq!(from_value::<f64>(return_val).unwrap(), 100.0);
+    }
+}
diff --git a/tests/js/test.js b/tests/js/test.js
index 3fbc177066..b895dfad00 100644
--- a/tests/js/test.js
+++ b/tests/js/test.js
@@ -1,2 +1,4 @@
-let a = "hello world";
-a;
+function jason(a, b) {
+  return arguments[0];
+}
+const val = jason(100, 6);