implement this

boa/src/environment/declarative_environment_record.rs

@@ -150,6 +150,10 @@ impl EnvironmentRecordTrait for DeclarativeEnvironmentRecord {
         false
     }
 
+    fn get_this_binding(&self) -> Value {
+        Gc::new(ValueData::Undefined)
+    }
+
     fn has_super_binding(&self) -> bool {
         false
     }

boa/src/environment/environment_record_trait.rs

@@ -60,6 +60,9 @@ pub trait EnvironmentRecordTrait: Debug + Trace + Finalize {
     /// Return true if it does and false if it does not.
     fn has_this_binding(&self) -> bool;
 
+    /// Return the `this` binding from the environment
+    fn get_this_binding(&self) -> Value;
+
     /// Determine if an Environment Record establishes a super method binding.
     /// Return true if it does and false if it does not.
     fn has_super_binding(&self) -> bool;

boa/src/environment/function_environment_record.rs

@@ -75,21 +75,6 @@ impl FunctionEnvironmentRecord {
             }
         }
     }
-
-    pub fn get_this_binding(&self) -> Value {
-        match self.this_binding_status {
-            BindingStatus::Lexical => {
-                // TODO: change this when error handling comes into play
-                panic!("There is no this for a lexical function record");
-            }
-            BindingStatus::Uninitialized => {
-                // TODO: change this when error handling comes into play
-                panic!("Reference Error: Unitialised binding for this function");
-            }
-
-            BindingStatus::Initialized => self.this_value.clone(),
-        }
-    }
 }
 
 impl EnvironmentRecordTrait for FunctionEnvironmentRecord {
@@ -116,6 +101,21 @@ impl EnvironmentRecordTrait for FunctionEnvironmentRecord {
         );
     }
 
+    fn get_this_binding(&self) -> Value {
+        match self.this_binding_status {
+            BindingStatus::Lexical => {
+                // TODO: change this when error handling comes into play
+                panic!("There is no this for a lexical function record");
+            }
+            BindingStatus::Uninitialized => {
+                // TODO: change this when error handling comes into play
+                panic!("Reference Error: Unitialised binding for this function");
+            }
+
+            BindingStatus::Initialized => self.this_value.clone(),
+        }
+    }
+
     fn create_immutable_binding(&mut self, name: String, strict: bool) -> bool {
         if self.env_rec.contains_key(&name) {
             // TODO: change this when error handling comes into play

boa/src/environment/global_environment_record.rs

@@ -29,10 +29,6 @@ pub struct GlobalEnvironmentRecord {
 }
 
 impl GlobalEnvironmentRecord {
-    pub fn get_this_binding(&self) -> Value {
-        self.global_this_binding.clone()
-    }
-
     pub fn has_var_declaration(&self, name: &str) -> bool {
         self.var_names.contains(name)
     }
@@ -91,6 +87,10 @@ impl GlobalEnvironmentRecord {
 }
 
 impl EnvironmentRecordTrait for GlobalEnvironmentRecord {
+    fn get_this_binding(&self) -> Value {
+        self.global_this_binding.clone()
+    }
+
     fn has_binding(&self, name: &str) -> bool {
         if self.declarative_record.has_binding(name) {
             return true;

boa/src/environment/lexical_environment.rs

@@ -113,6 +113,11 @@ impl LexicalEnvironment {
             .get_global_object()
     }
 
+    pub fn get_this_binding(&self) -> Value {
+        let env = self.environment_stack.get(0).expect("").borrow();
+        env.get_this_binding()
+    }
+
     pub fn create_mutable_binding(&mut self, name: String, deletion: bool, scope: VariableScope) {
         match scope {
             VariableScope::Block => self

boa/src/environment/object_environment_record.rs

@@ -91,6 +91,10 @@ impl EnvironmentRecordTrait for ObjectEnvironmentRecord {
         false
     }
 
+    fn get_this_binding(&self) -> Value {
+        Gc::new(ValueData::Undefined)
+    }
+
     fn has_super_binding(&self) -> bool {
         false
     }

boa/src/exec/mod.rs

@@ -569,6 +569,10 @@ impl Executor for Interpreter {
                 // TODO: for now we can do nothing but return the value as-is
                 Ok(Gc::new((*self.run(node)?).clone()))
             }
+            Node::This => {
+                // Will either return `this` binding or undefined
+                Ok(self.realm.environment.get_this_binding())
+            }
             ref i => unimplemented!("{}", i),
         }
     }