[FunctionDeclaration - execution] evaluate declaration into undefined not function (#473)

boa/src/builtins/value/tests.rs

@@ -128,7 +128,7 @@ fn get_types() {
         forward_val(&mut engine, "function foo() {console.log(\"foo\");}")
             .unwrap()
             .get_type(),
-        Type::Function
+        Type::Undefined
     );
     assert_eq!(
         forward_val(&mut engine, "null").unwrap().get_type(),

boa/src/exec/declaration/mod.rs

@@ -35,9 +35,9 @@ impl Executable for FunctionDecl {
         interpreter
             .realm_mut()
             .environment
-            .initialize_binding(self.name(), val.clone());
+            .initialize_binding(self.name(), val);
 
-        Ok(val)
+        Ok(Value::undefined())
     }
 }
 

boa/src/exec/tests.rs

@@ -1,5 +1,24 @@
 use crate::{builtins::Value, exec, exec::Interpreter, forward, realm::Realm};
 
+#[test]
+fn function_declaration_returns_undefined() {
+    let scenario = r#"
+        function abc() {}
+        "#;
+
+    assert_eq!(&exec(scenario), "undefined");
+}
+
+#[test]
+fn empty_var_decl_undefined() {
+    let scenario = r#"
+        let b;
+        b === undefined;
+        "#;
+
+    assert_eq!(&exec(scenario), "true");
+}
+
 #[test]
 fn property_accessor_member_expression_dot_notation_on_string_literal() {
     let scenario = r#"
@@ -59,16 +78,6 @@ fn semicolon_expression_stop() {
     assert_eq!(&exec(scenario), "1");
 }
 
-#[test]
-fn empty_var_decl_undefined() {
-    let scenario = r#"
-        let b;
-        b == undefined;
-        "#;
-
-    assert_eq!(&exec(scenario), "true");
-}
-
 #[test]
 fn object_field_set() {
     let scenario = r#"