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feat(transformer/nullish-coalescing-operator): add comments in top of file (#4972)

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part of #4881
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Dunqing 2024-08-20 01:06:35 +00:00
parent e331ca0a9d
commit 72ff2c67b9
1 changed files with 30 additions and 5 deletions
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35
crates/oxc_transformer/src/es2020/nullish_coalescing_operator.rs
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@ -1,3 +1,33 @@
//! ES2020: Nullish Coalescing Operator
//!
//! This plugin transforms nullish coalescing operators (`??`) to a series of ternary expressions.
//!
//! > This plugin is included in `preset-env`, in ES2020
//!
//! ## Example
//!
//! Input:
//! ```js
//! var foo = object.foo ?? "default";
//! ```
//!
//! Output:
//! ```js
//! var _object$foo;
//! var foo =
//! (_object$foo = object.foo) !== null && _object$foo !== void 0
//! ? _object$foo
//! : "default";
//! ```
//!
//! ## Implementation
//!
//! Implementation based on [@babel/plugin-transform-nullish-coalescing-operator](https://babeljs.io/docs/babel-plugin-transform-nullish-coalescing-operator).
//!
//! ## References:
//! * Babel plugin implementation: <https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-nullish-coalescing-operator>
//! * Nullish coalescing TC39 proposal: <https://github.com/tc39-transfer/proposal-nullish-coalescing>
use std::cell::Cell;
use oxc_semantic::{ReferenceFlag, SymbolFlags};
@ -10,11 +40,6 @@ use oxc_syntax::operator::{AssignmentOperator, BinaryOperator, LogicalOperator};
use crate::context::Ctx;
/// ES2020: Nullish Coalescing Operator
///
/// References:
/// * <https://babeljs.io/docs/babel-plugin-transform-nullish-coalescing-operator>
/// * <https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-nullish-coalescing-operator>
pub struct NullishCoalescingOperator<'a> {
_ctx: Ctx<'a>,
var_declarations: std::vec::Vec<Vec<'a, VariableDeclarator<'a>>>,