Cache well known symbols (#706)

boa/src/builtins/symbol/mod.rs

@@ -26,6 +26,200 @@ use crate::{
 };
 use gc::{Finalize, Trace};
 
+/// A structure that contains the JavaScript well known symbols.
+#[derive(Debug, Clone)]
+pub struct WellKnownSymbols {
+    async_iterator: RcSymbol,
+    has_instance: RcSymbol,
+    is_concat_spreadable: RcSymbol,
+    iterator: RcSymbol,
+    match_: RcSymbol,
+    match_all: RcSymbol,
+    replace: RcSymbol,
+    search: RcSymbol,
+    species: RcSymbol,
+    split: RcSymbol,
+    to_primitive: RcSymbol,
+    to_string_tag: RcSymbol,
+    unscopables: RcSymbol,
+}
+
+impl WellKnownSymbols {
+    pub(crate) fn new() -> (Self, u32) {
+        let mut count = 0;
+
+        let async_iterator = Symbol::new(count, Some("Symbol.asyncIterator".into())).into();
+        count += 1;
+        let has_instance = Symbol::new(count, Some("Symbol.hasInstance".into())).into();
+        count += 1;
+        let is_concat_spreadable =
+            Symbol::new(count, Some("Symbol.isConcatSpreadable".into())).into();
+        count += 1;
+        let iterator = Symbol::new(count, Some("Symbol.iterator".into())).into();
+        count += 1;
+        let match_ = Symbol::new(count, Some("Symbol.match".into())).into();
+        count += 1;
+        let match_all = Symbol::new(count, Some("Symbol.matchAll".into())).into();
+        count += 1;
+        let replace = Symbol::new(count, Some("Symbol.replace".into())).into();
+        count += 1;
+        let search = Symbol::new(count, Some("Symbol.search".into())).into();
+        count += 1;
+        let species = Symbol::new(count, Some("Symbol.species".into())).into();
+        count += 1;
+        let split = Symbol::new(count, Some("Symbol.split".into())).into();
+        count += 1;
+        let to_primitive = Symbol::new(count, Some("Symbol.toPrimitive".into())).into();
+        count += 1;
+        let to_string_tag = Symbol::new(count, Some("Symbol.toStringTag".into())).into();
+        count += 1;
+        let unscopables = Symbol::new(count, Some("Symbol.unscopables".into())).into();
+        count += 1;
+
+        (
+            Self {
+                async_iterator,
+                has_instance,
+                is_concat_spreadable,
+                iterator,
+                match_,
+                match_all,
+                replace,
+                search,
+                species,
+                split,
+                to_primitive,
+                to_string_tag,
+                unscopables,
+            },
+            count,
+        )
+    }
+
+    /// The `Symbol.asyncIterator` well known symbol.
+    ///
+    /// A method that returns the default AsyncIterator for an object.
+    /// Called by the semantics of the `for-await-of` statement.
+    #[inline]
+    pub fn async_iterator_symbol(&self) -> RcSymbol {
+        self.async_iterator.clone()
+    }
+
+    /// The `Symbol.hasInstance` well known symbol.
+    ///
+    /// A method that determines if a `constructor` object
+    /// recognizes an object as one of the `constructor`'s instances.
+    /// Called by the semantics of the instanceof operator.
+    #[inline]
+    pub fn has_instance_symbol(&self) -> RcSymbol {
+        self.async_iterator.clone()
+    }
+
+    /// The `Symbol.isConcatSpreadable` well known symbol.
+    ///
+    /// A Boolean valued property that if `true` indicates that
+    /// an object should be flattened to its array elements
+    /// by `Array.prototype.concat`.
+    #[inline]
+    pub fn is_concat_spreadable_symbol(&self) -> RcSymbol {
+        self.is_concat_spreadable.clone()
+    }
+
+    /// The `Symbol.iterator` well known symbol.
+    ///
+    /// A method that returns the default Iterator for an object.
+    /// Called by the semantics of the `for-of` statement.
+    #[inline]
+    pub fn iterator_symbol(&self) -> RcSymbol {
+        self.iterator.clone()
+    }
+
+    /// The `Symbol.match` well known symbol.
+    ///
+    /// A regular expression method that matches the regular expression
+    /// against a string. Called by the `String.prototype.match` method.
+    #[inline]
+    pub fn match_symbol(&self) -> RcSymbol {
+        self.match_.clone()
+    }
+
+    /// The `Symbol.matchAll` well known symbol.
+    ///
+    /// A regular expression method that returns an iterator, that yields
+    /// matches of the regular expression against a string.
+    /// Called by the `String.prototype.matchAll` method.
+    #[inline]
+    pub fn match_all_symbol(&self) -> RcSymbol {
+        self.match_all.clone()
+    }
+
+    /// The `Symbol.replace` well known symbol.
+    ///
+    /// A regular expression method that replaces matched substrings
+    /// of a string. Called by the `String.prototype.replace` method.
+    #[inline]
+    pub fn replace_symbol(&self) -> RcSymbol {
+        self.replace.clone()
+    }
+
+    /// The `Symbol.search` well known symbol.
+    ///
+    /// A regular expression method that returns the index within a
+    /// string that matches the regular expression.
+    /// Called by the `String.prototype.search` method.
+    #[inline]
+    pub fn search_symbol(&self) -> RcSymbol {
+        self.search.clone()
+    }
+
+    /// The `Symbol.species` well known symbol.
+    ///
+    /// A function valued property that is the `constructor` function
+    /// that is used to create derived objects.
+    #[inline]
+    pub fn species_symbol(&self) -> RcSymbol {
+        self.species.clone()
+    }
+
+    /// The `Symbol.split` well known symbol.
+    ///
+    /// A regular expression method that splits a string at the indices
+    /// that match the regular expression.
+    /// Called by the `String.prototype.split` method.
+    #[inline]
+    pub fn split_symbol(&self) -> RcSymbol {
+        self.split.clone()
+    }
+
+    /// The `Symbol.toPrimitive` well known symbol.
+    ///
+    /// A method that converts an object to a corresponding primitive value.
+    /// Called by the `ToPrimitive` (`Value::to_primitve`) abstract operation.
+    #[inline]
+    pub fn to_primitive_symbol(&self) -> RcSymbol {
+        self.to_primitive.clone()
+    }
+
+    /// The `Symbol.toStringTag` well known symbol.
+    ///
+    /// A String valued property that is used in the creation of the default
+    /// string description of an object.
+    /// Accessed by the built-in method `Object.prototype.toString`.
+    #[inline]
+    pub fn to_string_tag_symbol(&self) -> RcSymbol {
+        self.to_string_tag.clone()
+    }
+
+    /// The `Symbol.unscopables` well known symbol.
+    ///
+    /// An object valued property whose own and inherited property names are property
+    /// names that are excluded from the `with` environment bindings of the associated object.
+    #[inline]
+    pub fn unscopables_symbol(&self) -> RcSymbol {
+        self.unscopables.clone()
+    }
+}
+
 #[derive(Debug, Finalize, Trace, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct Symbol {
     hash: u32,
@@ -109,32 +303,32 @@ impl Symbol {
 
     /// Initialise the `Symbol` object on the global object.
     #[inline]
-    pub fn init(interpreter: &mut Context) -> (&'static str, Value) {
+    pub fn init(context: &mut Context) -> (&'static str, Value) {
         // Define the Well-Known Symbols
         // https://tc39.es/ecma262/#sec-well-known-symbols
-        let symbol_async_iterator =
-            interpreter.construct_symbol(Some("Symbol.asyncIterator".into()));
-        let symbol_has_instance = interpreter.construct_symbol(Some("Symbol.hasInstance".into()));
-        let symbol_is_concat_spreadable =
-            interpreter.construct_symbol(Some("Symbol.isConcatSpreadable".into()));
-        let symbol_iterator = interpreter.construct_symbol(Some("Symbol.iterator".into()));
-        let symbol_match = interpreter.construct_symbol(Some("Symbol.match".into()));
-        let symbol_match_all = interpreter.construct_symbol(Some("Symbol.matchAll".into()));
-        let symbol_replace = interpreter.construct_symbol(Some("Symbol.replace".into()));
-        let symbol_search = interpreter.construct_symbol(Some("Symbol.search".into()));
-        let symbol_species = interpreter.construct_symbol(Some("Symbol.species".into()));
-        let symbol_split = interpreter.construct_symbol(Some("Symbol.split".into()));
-        let symbol_to_primitive = interpreter.construct_symbol(Some("Symbol.toPrimitive".into()));
-        let symbol_to_string_tag = interpreter.construct_symbol(Some("Symbol.toStringTag".into()));
-        let symbol_unscopables = interpreter.construct_symbol(Some("Symbol.unscopables".into()));
-
-        let global = interpreter.global_object();
+        let well_known_symbols = context.well_known_symbols();
+
+        let symbol_async_iterator = well_known_symbols.async_iterator_symbol();
+        let symbol_has_instance = well_known_symbols.has_instance_symbol();
+        let symbol_is_concat_spreadable = well_known_symbols.is_concat_spreadable_symbol();
+        let symbol_iterator = well_known_symbols.iterator_symbol();
+        let symbol_match = well_known_symbols.match_symbol();
+        let symbol_match_all = well_known_symbols.match_all_symbol();
+        let symbol_replace = well_known_symbols.replace_symbol();
+        let symbol_search = well_known_symbols.search_symbol();
+        let symbol_species = well_known_symbols.species_symbol();
+        let symbol_split = well_known_symbols.split_symbol();
+        let symbol_to_primitive = well_known_symbols.to_primitive_symbol();
+        let symbol_to_string_tag = well_known_symbols.to_string_tag_symbol();
+        let symbol_unscopables = well_known_symbols.unscopables_symbol();
+
+        let global = context.global_object();
         let _timer = BoaProfiler::global().start_event(Self::NAME, "init");
 
         // Create prototype object
         let prototype = Value::new_object(Some(global));
 
-        make_builtin_fn(Self::to_string, "toString", &prototype, 0, interpreter);
+        make_builtin_fn(Self::to_string, "toString", &prototype, 0, context);
 
         let symbol_object = make_constructor_fn(
             Self::NAME,

boa/src/context.rs

@@ -4,7 +4,8 @@ use crate::{
     builtins::{
         self,
         function::{Function, FunctionFlags, NativeFunction},
-        Console, Symbol,
+        symbol::{Symbol, WellKnownSymbols},
+        Console,
     },
     class::{Class, ClassBuilder},
     exec::Interpreter,
@@ -46,17 +47,22 @@ pub struct Context {
 
     /// console object state.
     console: Console,
+
+    /// Cached well known symbols
+    well_known_symbols: WellKnownSymbols,
 }
 
 impl Default for Context {
     fn default() -> Self {
         let realm = Realm::create();
         let executor = Interpreter::new();
+        let (well_known_symbols, symbol_count) = WellKnownSymbols::new();
         let mut context = Self {
             realm,
             executor,
-            symbol_count: 0,
+            symbol_count,
             console: Console::default(),
+            well_known_symbols,
         };
 
         // Add new builtIns to Context Realm
@@ -495,4 +501,20 @@ impl Context {
 
         result
     }
+
+    /// Returns a structure that contains the JavaScript well known symbols.
+    ///
+    /// # Examples
+    /// ```
+    ///# use boa::Context;
+    /// let mut context = Context::new();
+    ///
+    /// let iterator = context.well_known_symbols().iterator_symbol();
+    /// assert_eq!(iterator.description(), Some("Symbol.iterator"));
+    /// ```
+    /// This is equivalent to `let iterator = Symbol.iterator` in JavaScript.
+    #[inline]
+    pub fn well_known_symbols(&self) -> &WellKnownSymbols {
+        &self.well_known_symbols
+    }
 }