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//! This module implements the `Attribute` struct which contains the attibutes for property descriptors. use crate::gc::{empty_trace, Finalize, Trace}; use bitflags::bitflags; #[cfg(test)] mod tests; bitflags! { /// This struct constains the property flags as describen in the ECMAScript specification. /// /// It contains the following flags: /// - `[[Writable]]` (`WRITABLE`) - If `false`, attempts by ECMAScript code to change the property's /// `[[Value]]` attribute using `[[Set]]` will not succeed. /// - `[[Enumerable]]` (`ENUMERABLE`) - If the property will be enumerated by a for-in enumeration. /// - `[[Configurable]]` (`CONFIGURABLE`) - If `false`, attempts to delete the property, /// change the property to be an `accessor property`, or change its attributes (other than `[[Value]]`, /// or changing `[[Writable]]` to `false`) will fail. #[derive(Finalize)] pub struct Attribute: u8 { /// The `Writable` attribute decides whether the value associated with the property can be changed or not, from its initial value. const WRITABLE = 0b0000_0001; /// If the property can be enumerated by a `for-in` loop. const ENUMERABLE = 0b0000_0010; /// If the property descriptor can be changed later. const CONFIGURABLE = 0b0000_0100; /// The property is not writable. const READONLY = 0b0000_0000; /// The property can not be enumerated in a `for-in` loop. const NON_ENUMERABLE = 0b0000_0000; /// The property descriptor cannot be changed. const PERMANENT = 0b0000_0000; } } // We implement `Trace` manualy rather that wih derive, beacuse `rust-gc`, // derive `Trace` does not allow `Copy` and `Trace` to be both implemented. // // SAFETY: The `Attribute` struct only contains an `u8` // and therefore it should be safe to implement an empty trace. unsafe impl Trace for Attribute { empty_trace!(); } impl Attribute { /// Clear all flags. #[inline] pub fn clear(&mut self) { self.bits = 0; } /// Sets the `writable` flag. #[inline] pub fn set_writable(&mut self, value: bool) { if value { *self |= Self::WRITABLE; } else { *self |= *self & !Self::WRITABLE; } } /// Gets the `writable` flag. #[inline] pub fn writable(self) -> bool { self.contains(Self::WRITABLE) } /// Sets the `enumerable` flag. #[inline] pub fn set_enumerable(&mut self, value: bool) { if value { *self |= Self::ENUMERABLE; } else { *self |= *self & !Self::ENUMERABLE; } } /// Gets the `enumerable` flag. #[inline] pub fn enumerable(self) -> bool { self.contains(Self::ENUMERABLE) } /// Sets the `configurable` flag. #[inline] pub fn set_configurable(&mut self, value: bool) { if value { *self |= Self::CONFIGURABLE; } else { *self |= *self & !Self::CONFIGURABLE; } } /// Gets the `configurable` flag. #[inline] pub fn configurable(self) -> bool { self.contains(Self::CONFIGURABLE) } } impl Default for Attribute { /// Returns the default flags according to the [ECMAScript specification][spec]. /// /// [spec]: https://tc39.es/ecma262/#table-default-attribute-values fn default() -> Self { Self::READONLY | Self::NON_ENUMERABLE | Self::PERMANENT } }