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feat(transformer/class-properties): do not create temp var for template literal computed key (#7919)

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Do not create temp var for computed key which is `TemplateLiteral` with no expressions. Evaluating such a template literal cannot have side effects.

```js
class C {
  [`foo`] = 1;
}
```

But this *can* have side effects:

```js
class C {
  [`foo${bar}`] = 1;
}
```
This commit is contained in:
overlookmotel 2024-12-15 16:55:00 +00:00
parent b31f123b7f
commit 02b653c061
1 changed files with 6 additions and 0 deletions
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6
crates/oxc_transformer/src/es2022/class_properties/computed_key.rs
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@ -112,6 +112,12 @@ fn key_needs_temp_var(key: &Expression, ctx: &TraverseCtx) -> bool {
| Expression::BigIntLiteral(_)
| Expression::RegExpLiteral(_)
| Expression::StringLiteral(_) => false,
// Template literal cannot have side effects if it has no expressions.
// If it *does* have expressions, but they're all literals, then also cannot have side effects,
// but don't bother checking for that as it shouldn't occur in real world code.
// Why would you write "`x${9}z`" when you can just write "`x9z`"?
// Note: "`x${foo}`" *can* have side effects if `foo` is an object with a `valueOf` method.
Expression::TemplateLiteral(lit) => !lit.expressions.is_empty(),
// `IdentifierReference`s can have side effects if is unbound.
//
// If var is mutated, it also needs a temp var, because of cases like