Privatize JsValue's internals and expose it through a JsVariant (with immutable reference)

cli/src/debug/gc.rs

@@ -5,7 +5,7 @@ use boa_engine::{
 /// Trigger garbage collection.
 fn collect(_: &JsValue, _: &[JsValue], _: &mut Context) -> JsResult<JsValue> {
     boa_gc::force_collect();
-    Ok(JsValue::undefined())
+    Ok(JsValue::UNDEFINED)
 }
 
 pub(super) fn create_object(context: &mut Context) -> JsObject {

cli/src/debug/limits.rs

@@ -13,7 +13,7 @@ fn get_loop(_: &JsValue, _: &[JsValue], context: &mut Context) -> JsResult<JsVal
 fn set_loop(_: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
     let value = args.get_or_undefined(0).to_length(context)?;
     context.runtime_limits_mut().set_loop_iteration_limit(value);
-    Ok(JsValue::undefined())
+    Ok(JsValue::UNDEFINED)
 }
 
 fn get_stack(_: &JsValue, _: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
@@ -29,7 +29,7 @@ fn set_stack(_: &JsValue, args: &[JsValue], context: &mut Context) -> JsResult<J
             .into());
     };
     context.runtime_limits_mut().set_stack_size_limit(value);
-    Ok(JsValue::undefined())
+    Ok(JsValue::UNDEFINED)
 }
 
 fn get_recursion(_: &JsValue, _: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
@@ -45,7 +45,7 @@ fn set_recursion(_: &JsValue, args: &[JsValue], context: &mut Context) -> JsResu
             .into());
     };
     context.runtime_limits_mut().set_recursion_limit(value);
-    Ok(JsValue::undefined())
+    Ok(JsValue::UNDEFINED)
 }
 
 pub(super) fn create_object(context: &mut Context) -> JsObject {

cli/src/debug/optimizer.rs

@@ -18,7 +18,7 @@ fn set_constant_folding(_: &JsValue, args: &[JsValue], context: &mut Context) ->
     let mut options = context.optimizer_options();
     options.set(OptimizerOptions::CONSTANT_FOLDING, value);
     context.set_optimizer_options(options);
-    Ok(JsValue::undefined())
+    Ok(JsValue::UNDEFINED)
 }
 
 fn get_statistics(_: &JsValue, _: &[JsValue], context: &mut Context) -> JsResult<JsValue> {
@@ -33,7 +33,7 @@ fn set_statistics(_: &JsValue, args: &[JsValue], context: &mut Context) -> JsRes
     let mut options = context.optimizer_options();
     options.set(OptimizerOptions::STATISTICS, value);
     context.set_optimizer_options(options);
-    Ok(JsValue::undefined())
+    Ok(JsValue::UNDEFINED)
 }
 
 pub(super) fn create_object(context: &mut Context) -> JsObject {

core/engine/src/builtins/array/mod.rs

@@ -38,7 +38,9 @@ use std::cmp::{min, Ordering};
 use super::{BuiltInBuilder, BuiltInConstructor, IntrinsicObject};
 
 mod array_iterator;
+use crate::value::JsVariant;
 pub(crate) use array_iterator::ArrayIterator;
+
 #[cfg(test)]
 mod tests;
 
@@ -537,9 +539,9 @@ impl Array {
         // 3. Else,
         //     a. If IsCallable(mapfn) is false, throw a TypeError exception.
         //     b. Let mapping be true.
-        let mapping = match mapfn {
-            JsValue::Undefined => None,
-            JsValue::Object(o) if o.is_callable() => Some(o),
+        let mapping = match mapfn.variant() {
+            JsVariant::Undefined => None,
+            JsVariant::Object(o) if o.is_callable() => Some(o),
             _ => {
                 return Err(JsNativeError::typ()
                     .with_message(format!("`{}` is not callable", mapfn.type_of()))
@@ -2665,9 +2667,9 @@ impl Array {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         // 1. If comparefn is not undefined and IsCallable(comparefn) is false, throw a TypeError exception.
-        let comparefn = match args.get_or_undefined(0) {
-            JsValue::Object(ref obj) if obj.is_callable() => Some(obj),
-            JsValue::Undefined => None,
+        let comparefn = match args.get_or_undefined(0).variant() {
+            JsVariant::Object(obj) if obj.is_callable() => Some(obj),
+            JsVariant::Undefined => None,
             _ => {
                 return Err(JsNativeError::typ()
                     .with_message("The comparison function must be either a function or undefined")
@@ -2728,9 +2730,9 @@ impl Array {
         context: &mut Context,
     ) -> JsResult<JsValue> {
         // 1. If comparefn is not undefined and IsCallable(comparefn) is false, throw a TypeError exception.
-        let comparefn = match args.get_or_undefined(0) {
-            JsValue::Object(ref obj) if obj.is_callable() => Some(obj),
-            JsValue::Undefined => None,
+        let comparefn = match args.get_or_undefined(0).variant() {
+            JsVariant::Object(obj) if obj.is_callable() => Some(obj),
+            JsVariant::Undefined => None,
             _ => {
                 return Err(JsNativeError::typ()
                     .with_message("The comparison function must be either a function or undefined")
@@ -3319,7 +3321,7 @@ fn compare_array_elements(
         let args = [x.clone(), y.clone()];
         //     a. Let v be ? ToNumber(? Call(comparefn, undefined, « x, y »)).
         let v = cmp
-            .call(&JsValue::Undefined, &args, context)?
+            .call(&JsValue::UNDEFINED, &args, context)?
             .to_number(context)?;
         //     b. If v is NaN, return +0𝔽.
         //     c. Return v.

core/engine/src/builtins/array/tests.rs

@@ -875,7 +875,8 @@ fn array_spread_non_iterable() {
 fn get_relative_start() {
     #[track_caller]
     fn assert(context: &mut Context, arg: Option<&JsValue>, len: u64, expected: u64) {
-        let arg = arg.unwrap_or(&JsValue::Undefined);
+        const UNDEFINED: &JsValue = &JsValue::UNDEFINED;
+        let arg = arg.unwrap_or(UNDEFINED);
         assert_eq!(
             Array::get_relative_start(context, arg, len).unwrap(),
             expected
@@ -902,7 +903,8 @@ fn get_relative_start() {
 fn get_relative_end() {
     #[track_caller]
     fn assert(context: &mut Context, arg: Option<&JsValue>, len: u64, expected: u64) {
-        let arg = arg.unwrap_or(&JsValue::Undefined);
+        const UNDEFINED: &JsValue = &JsValue::UNDEFINED;
+        let arg = arg.unwrap_or(UNDEFINED);
         assert_eq!(
             Array::get_relative_end(context, arg, len).unwrap(),
             expected

core/engine/src/builtins/array_buffer/mod.rs

@@ -880,7 +880,7 @@ impl ArrayBuffer {
                 // 8. If allocatingResizableBuffer is true, then
                 //    c. Set obj.[[ArrayBufferMaxByteLength]] to maxByteLength.
                 max_byte_len,
-                detach_key: JsValue::Undefined,
+                detach_key: JsValue::UNDEFINED,
             },
         );
 

core/engine/src/builtins/date/mod.rs

@@ -423,7 +423,7 @@ impl Date {
 
         // 4. If t is NaN, return NaN.
         if t.is_nan() {
-            return Ok(JsValue::from(f64::NAN));
+            return Ok(JsValue::NAN);
         };
 
         if LOCAL {

core/engine/src/builtins/function/mod.rs

@@ -511,12 +511,12 @@ impl BuiltInFunctionObject {
             // It is a Syntax Error if FormalParameters Contains YieldExpression is true.
             if generator && contains(&parameters, ContainsSymbol::YieldExpression) {
                 return Err(JsNativeError::syntax().with_message(
-                        if r#async {
-                            "yield expression is not allowed in formal parameter list of async generator"
-                        } else {
-                            "yield expression is not allowed in formal parameter list of generator"
-                        }
-                    ).into());
+                    if r#async {
+                        "yield expression is not allowed in formal parameter list of async generator"
+                    } else {
+                        "yield expression is not allowed in formal parameter list of generator"
+                    }
+                ).into());
             }
 
             // It is a Syntax Error if FormalParameters Contains AwaitExpression is true.
@@ -735,7 +735,7 @@ impl BuiltInFunctionObject {
         let f = BoundFunction::create(target.clone(), this_arg, bound_args, context)?;
 
         // 4. Let L be 0.
-        let mut l = JsValue::new(0);
+        let mut l = JsValue::ZERO;
 
         // 5. Let targetHasLength be ? HasOwnProperty(Target, "length").
         // 6. If targetHasLength is true, then

core/engine/src/builtins/intl/locale/mod.rs

@@ -649,7 +649,7 @@ impl Locale {
             .keywords
             .get(&key!("kn"))
             .map(Value::as_tinystr_slice);
-        Ok(JsValue::Boolean(match kn {
+        Ok(JsValue::new(match kn {
             Some([]) => true,
             Some([kn]) if kn == "true" => true,
             _ => false,

core/engine/src/builtins/intl/mod.rs

@@ -174,7 +174,7 @@ impl Intl {
         let ll = locale::canonicalize_locale_list(locales, context)?;
 
         // 2. Return CreateArrayFromList(ll).
-        Ok(JsValue::Object(Array::create_array_from_list(
+        Ok(JsValue::new(Array::create_array_from_list(
             ll.into_iter().map(|loc| js_string!(loc.to_string()).into()),
             context,
         )))

core/engine/src/builtins/intl/number_format/mod.rs

@@ -19,6 +19,12 @@ use num_bigint::BigInt;
 use num_traits::Num;
 pub(crate) use options::*;
 
+use super::{
+    locale::{canonicalize_locale_list, filter_locales, resolve_locale, validate_extension},
+    options::{coerce_options_to_object, IntlOptions},
+    Service,
+};
+use crate::value::JsVariant;
 use crate::{
     builtins::{
         builder::BuiltInBuilder, options::get_option, string::is_trimmable_whitespace,
@@ -41,12 +47,6 @@ use crate::{
     NativeFunction,
 };
 
-use super::{
-    locale::{canonicalize_locale_list, filter_locales, resolve_locale, validate_extension},
-    options::{coerce_options_to_object, IntlOptions},
-    Service,
-};
-
 #[cfg(test)]
 mod tests;
 
@@ -338,7 +338,7 @@ impl BuiltInConstructor for NumberFormat {
                 break 'block default_use_grouping;
             }
             // 3. If value is true, return true.
-            if let &JsValue::Boolean(true) = &value {
+            if let Some(true) = value.as_boolean() {
                 break 'block GroupingStrategy::Always;
             }
 
@@ -750,8 +750,8 @@ fn unwrap_number_format(nf: &JsValue, context: &mut Context) -> JsResult<JsObjec
 
         //    a. Return ? Get(nf, %Intl%.[[FallbackSymbol]]).
         let nf = nf_o.get(fallback_symbol, context)?;
-        if let JsValue::Object(nf) = nf {
-            if let Ok(nf) = nf.downcast::<NumberFormat>() {
+        if let Some(nf) = nf.as_object() {
+            if let Ok(nf) = nf.clone().downcast::<NumberFormat>() {
                 return Ok(nf);
             }
         }
@@ -771,16 +771,16 @@ fn to_intl_mathematical_value(value: &JsValue, context: &mut Context) -> JsResul
 
     // TODO: Add support in `FixedDecimal` for infinity and NaN, which
     // should remove the returned errors.
-    match prim_value {
+    match prim_value.variant() {
         // 2. If Type(primValue) is BigInt, return ℝ(primValue).
-        JsValue::BigInt(bi) => {
+        JsVariant::BigInt(bi) => {
             let bi = bi.to_string();
             FixedDecimal::try_from(bi.as_bytes())
                 .map_err(|err| JsNativeError::range().with_message(err.to_string()).into())
         }
         // 3. If Type(primValue) is String, then
         //     a. Let str be primValue.
-        JsValue::String(s) => {
+        JsVariant::String(s) => {
             // 5. Let text be StringToCodePoints(str).
             // 6. Let literal be ParseText(text, StringNumericLiteral).
             // 7. If literal is a List of errors, return not-a-number.
@@ -791,18 +791,18 @@ fn to_intl_mathematical_value(value: &JsValue, context: &mut Context) -> JsResul
             //     c. If rounded is +∞𝔽, return positive-infinity.
             //     d. If rounded is +0𝔽 and intlMV < 0, return negative-zero.
             //     e. If rounded is +0𝔽, return 0.
-            js_string_to_fixed_decimal(&s).ok_or_else(|| {
+            js_string_to_fixed_decimal(s).ok_or_else(|| {
                 JsNativeError::syntax()
                     .with_message("could not parse the provided string")
                     .into()
             })
         }
         // 4. Else,
-        other => {
+        _ => {
             // a. Let x be ? ToNumber(primValue).
             // b. If x is -0𝔽, return negative-zero.
             // c. Let str be Number::toString(x, 10).
-            let x = other.to_number(context)?;
+            let x = prim_value.to_number(context)?;
 
             FixedDecimal::try_from_f64(x, FloatPrecision::Floating)
                 .map_err(|err| JsNativeError::range().with_message(err.to_string()).into())

core/engine/src/builtins/iterable/async_from_sync_iterator.rs

@@ -172,7 +172,7 @@ impl AsyncFromSyncIterator {
                 // b. Perform ! Call(promiseCapability.[[Resolve]], undefined, « iterResult »).
                 promise_capability
                     .resolve()
-                    .call(&JsValue::Undefined, &[iter_result], context)
+                    .call(&JsValue::UNDEFINED, &[iter_result], context)
                     .expect("cannot fail according to spec");
 
                 // c. Return promiseCapability.[[Promise]].

core/engine/src/builtins/iterable/mod.rs

@@ -314,8 +314,8 @@ impl IteratorResult {
     /// Gets a new `IteratorResult` from a value. Returns `Err` if
     /// the value is not a [`JsObject`]
     pub(crate) fn from_value(value: JsValue) -> JsResult<Self> {
-        if let JsValue::Object(o) = value {
-            Ok(Self { object: o })
+        if let Some(object) = value.into_object() {
+            Ok(Self { object })
         } else {
             Err(JsNativeError::typ()
                 .with_message("next value should be an object")

core/engine/src/builtins/map/mod.rs

@@ -33,7 +33,9 @@ mod map_iterator;
 pub(crate) use map_iterator::MapIterator;
 
 pub mod ordered_map;
+use crate::value::JsVariant;
 use ordered_map::OrderedMap;
+
 #[cfg(test)]
 mod tests;
 
@@ -238,11 +240,11 @@ impl Map {
             // 2. Perform ? RequireInternalSlot(M, [[MapData]]).
             // 3. Let entries be the List that is M.[[MapData]].
             if let Some(mut map) = object.downcast_mut::<OrderedMap<JsValue>>() {
-                let key = match key {
-                    JsValue::Rational(r) => {
+                let key = match key.variant() {
+                    JsVariant::Float64(r) => {
                         // 5. If key is -0𝔽, set key to +0𝔽.
                         if r.is_zero() {
-                            JsValue::Rational(0f64)
+                            JsValue::ZERO
                         } else {
                             key.clone()
                         }
@@ -306,10 +308,9 @@ impl Map {
     /// [spec]: https://tc39.es/ecma262/#sec-map.prototype.delete
     /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/delete
     pub(crate) fn delete(this: &JsValue, args: &[JsValue], _: &mut Context) -> JsResult<JsValue> {
-        const JS_ZERO: &JsValue = &JsValue::Integer(0);
         let key = args.get_or_undefined(0);
         let key = match key.as_number() {
-            Some(n) if n.is_zero() => JS_ZERO,
+            Some(n) if n.is_zero() => &JsValue::ZERO,
             _ => key,
         };
 
@@ -342,15 +343,14 @@ impl Map {
     /// [spec]: https://tc39.es/ecma262/#sec-map.prototype.get
     /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/get
     pub(crate) fn get(this: &JsValue, args: &[JsValue], _: &mut Context) -> JsResult<JsValue> {
-        const JS_ZERO: &JsValue = &JsValue::Integer(0);
         let key = args.get_or_undefined(0);
         let key = match key.as_number() {
-            Some(n) if n.is_zero() => JS_ZERO,
+            Some(n) if n.is_zero() => &JsValue::ZERO,
             _ => key,
         };
 
         // 1. Let M be the this value.
-        if let JsValue::Object(ref object) = this {
+        if let Some(object) = this.as_object() {
             // 2. Perform ? RequireInternalSlot(M, [[MapData]]).
             // 3. Let entries be the List that is M.[[MapData]].
             if let Some(map) = object.downcast_ref::<OrderedMap<JsValue>>() {
@@ -407,15 +407,14 @@ impl Map {
     /// [spec]: https://tc39.es/ecma262/#sec-map.prototype.has
     /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/has
     pub(crate) fn has(this: &JsValue, args: &[JsValue], _: &mut Context) -> JsResult<JsValue> {
-        const JS_ZERO: &JsValue = &JsValue::Integer(0);
         let key = args.get_or_undefined(0);
         let key = match key.as_number() {
-            Some(n) if n.is_zero() => JS_ZERO,
+            Some(n) if n.is_zero() => &JsValue::ZERO,
             _ => key,
         };
 
         // 1. Let M be the this value.
-        if let JsValue::Object(ref object) = this {
+        if let Some(object) = this.as_object() {
             // 2. Perform ? RequireInternalSlot(M, [[MapData]]).
             // 3. Let entries be the List that is M.[[MapData]].
             if let Some(map) = object.downcast_ref::<OrderedMap<JsValue>>() {

core/engine/src/builtins/number/globals.rs

@@ -254,7 +254,7 @@ pub(crate) fn parse_int(_: &JsValue, args: &[JsValue], context: &mut Context) ->
             return Ok(JsValue::new(-0_f64));
         }
 
-        return Ok(JsValue::new(0_f64));
+        return Ok(JsValue::ZERO);
     }
 
     // 16. Return 𝔽(sign × mathInt).