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docs(syntax): more comments for ReferenceFlags (#7392)

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Add more docs to `ReferenceFlags`, mainly to include the runtime test in https://github.com/oxc-project/oxc/issues/5165#issuecomment-2488333549.
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overlookmotel 2024-11-21 11:20:28 +00:00
parent a32f5a73d3
commit b3d5802ef1
1 changed files with 25 additions and 9 deletions
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34
crates/oxc_syntax/src/reference.rs
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@ -53,6 +53,22 @@ bitflags! {
/// 2. Types being referenced as types
/// 3. Values being used in type contexts
///
/// ## Values
/// Whether a reference is considered [`Read`] or [`Write`] is determined according to ECMA spec.
///
/// See comments on [`Read`] and [`Write`] below.
///
/// Counter-intuitively, `y` in `x = y = z` is [`Write`] only. `x = y = z` is equivalent to:
///
/// ```js
/// var _temp = z;
/// y = _temp;
/// x = _temp;
/// ```
///
/// See <https://github.com/oxc-project/oxc/issues/5165#issuecomment-2488333549> for a runtime test
/// to determine Read/Write operations in a code snippet.
///
/// ## Value as Type
/// The [`ValueAsType`] flag is a temporary marker for references that need to
/// resolve to value symbols initially, but will ultimately be treated as type references.
@ -76,12 +92,12 @@ bitflags! {
#[cfg_attr(feature = "serialize", derive(Serialize))]
pub struct ReferenceFlags: u8 {
const None = 0;
/// A symbol is being read as a Value.
/// Symbol is being read from as a Value.
///
/// This value can be derived from the spec:
/// Whether a reference is `Read` is as defined in the spec:
///
/// Under `Runtime Semantics: Evaluation`, when [`GetValue`](https://tc39.es/ecma262/#sec-getvalue) is called
/// on a expression, and the expression is an `IdentifierReference`.
/// Under `Runtime Semantics: Evaluation`, when [`GetValue`](https://tc39.es/ecma262/#sec-getvalue)
/// is called on a expression, and the expression is an `IdentifierReference`.
///
/// For example:
/// ```text
@ -89,12 +105,12 @@ bitflags! {
/// 2. Perform ? GetValue(lRef).
/// ```
const Read = 1 << 0;
/// A symbol is being written to in a Value context.
/// Symbol is being written to as a Value.
///
/// This value can be derived from the spec:
/// Whether a reference is `Write` is as defined in the spec:
///
/// Under `Runtime Semantics: Evaluation`, when [`PutValue`](https://tc39.es/ecma262/#sec-putvalue) is called
/// on a expression, and the expression is an `IdentifierReference`.
/// Under `Runtime Semantics: Evaluation`, when [`PutValue`](https://tc39.es/ecma262/#sec-putvalue)
/// is called on a expression, and the expression is an `IdentifierReference`.
///
/// For example:
/// ```text
@ -109,7 +125,7 @@ bitflags! {
/// The symbol being referenced is a value.
///
/// Note that this does not necessarily indicate the reference is used
/// in a value context, since type queries are also flagged as [`Read`]
/// in a value context, since type queries are also flagged as [`Read`].
///
/// [`Read`]: ReferenceFlags::Read
const Value = Self::Read.bits() | Self::Write.bits();