Preserve parentheses around TypeScript instantiation expressions in postfix contexts. Previously, `(f<T>).x` and `(f<T>)[x]` were emitted as `f<T>.x` and `f<T>[x]`, producing invalid syntax or changing how the expression is parsed.
The printer now respects the surrounding precedence while retaining grouping for lower-precedence operands.
`packages/codegen` drops required parentheses around the right operand of a private-in expression when that operand is another relational expression. This changes which value the private-field check receives and can change observable behavior.
For example, this input throws a `TypeError`:
```js
class C {
#x;
test(a, b) {
return #x in (a instanceof b);
}
}
new C().test({}, Object);
```
`a instanceof b` evaluates to `true`, but a private-field check requires an object on its right-hand side.
The JavaScript printer previously emitted:
```js
return #x in a instanceof b;
```
Relational operators associate to the left, so that output is parsed as `(#x in a) instanceof b`. The private-field check on `{}` produces `false`, and `false instanceof Object` returns `false` instead of throwing.
The printer now preserves the original grouping:
```js
return #x in (a instanceof b);
```
`printPrivateInExpression` now prints its right operand with `PREC_COMPARE` instead of `PREC_EQUALS`. The expression printers wrap operands whose precedence is equal to or lower than the requested precedence, so the comparison threshold retains parentheses around `<`, `<=`, `>`, `>=`, `instanceof`, and nested private-in expressions. The now-unused `PREC_EQUALS` import is removed.
Equality and lower-precedence operands continue to retain their required grouping. Shift, arithmetic, and exponentiation operands can still omit unnecessary parentheses. The existing `CTX_FORBID_IN` handling remains in place.
This applies to both ordinary and source-map-enabled printer builds and brings the JavaScript implementation in line with the Rust fix in #26411. It addresses grouping of the private-in right operand, separately from the left-operand correction in #26403.
`packages/codegen` can turn valid JavaScript into unparseable output when a `yield` expression appears in a classic `for` loop initializer and its argument contains an `in` operator.
For example, this input is valid:
```js
function* g(o) {
for (yield (1 in o); false;);
}
```
The JavaScript printer previously dropped the required grouping:
```js
function* g(o) {
for (yield 1 in o; false;);
}
```
An unparenthesized `in` is not allowed at this position in a classic `for` initializer. The same problem affects `yield*`, nested yields, and assignments inside the yield argument.
The printer now preserves the parentheses:
```js
function* g(o) {
for (yield (1 in o); false;);
}
```
The `for` printer already marks its initializer with `CTX_FORBID_IN`, but `printYieldExpression` discarded that context and printed its argument with `CTX_NONE`. The yield dispatch now passes its incoming context to `printYieldExpression`, which forwards only `CTX_FORBID_IN` to the argument when the yield expression is unwrapped. The argument retains its existing `PREC_YIELD` precedence.
When precedence requires parentheses around the entire yield expression, those parentheses already permit `in` inside. The argument context is cleared in that case, avoiding redundant inner parentheses:
```js
// Input
function* g(o) {
for ((yield (1 in o)) + 1; false;);
}
// Output
function* g(o) {
for ((yield 1 in o) + 1; false;);
}
```
Both `yield` and `yield*` use this path. Outside a restricted initializer, ordinary yields continue to omit unnecessary grouping: `yield (1 in o)` prints as `yield 1 in o`.
The correction applies to both ordinary and source-map-enabled builds and brings the JavaScript printer in line with the Rust fix in #26413.
Oxc codegen npm package emits invalid JavaScript when a quoted imported name matches its local binding. The printer compares the decoded names and omits the alias, but leaves the imported name quoted. A quoted import name requires an explicit `as` binding.
For this valid input:
```js
import { "foo" as foo } from "m";
```
The JavaScript printer previously emitted:
```js
import { "foo" } from "m";
```
It now prints the matching local binding as identifier shorthand:
```js
import { foo } from "m";
```
`printImportDeclaration` checks for a string-literal imported name whose decoded value equals the local binding name before printing the imported name. In that case, it prints the local identifier directly, including its source-map mapping. The local binding already supplies a valid identifier, so this requires neither a separate identifier-validity check nor an AST mutation.
Comparing the decoded value also handles escaped and Unicode import names:
```js
// Input
import { "a\u0062" as ab } from "m";
import { "π" as π } from "m";
// Output
import { ab } from "m";
import { π } from "m";
```
Declaration-level and inline TypeScript type imports use the same shorthand:
```ts
// Input
import type { "Foo" as Foo } from "m";
import { type "Bar" as Bar } from "m";
// Output
import type { Foo } from "m";
import { type Bar } from "m";
```
Quoted names that differ from their local bindings retain their quotes and aliases, including `"foo-bar" as foo`, `"" as foo`, and `"default" as foo`. Ordinary identifier imports keep their existing shorthand behavior. The correction applies to both the ordinary and source-map-enabled builds and brings the JavaScript printer in line with the Rust codegen fix in #26386.
The codegen npm package drops required parentheses when a private-in expression is the left operand of a higher-precedence binary operator. The generated JavaScript can evaluate a different expression and throw a runtime error.
For example, this input returns `2`:
```js
class C {
#x;
test(o) {
return (#x in o) + 1;
}
}
console.log(new C().test(new C()));
```
The JavaScript printer previously emitted the return expression as:
```js
return #x in o + 1;
```
Because `+` binds more tightly than `in`, that output is parsed as `#x in (o + 1)`. Adding `1` to the object produces a primitive, so the private-field check throws a `TypeError` instead of producing the boolean used by the original addition.
The printer now preserves the grouping:
```js
return (#x in o) + 1;
```
The iterative binary-expression printer already computes the precedence required for each left operand. Its private-in special case discarded that value and passed `PREC_LOWEST` to `printPrivateInExpression`. Passing `v.leftPrecedence` instead lets the existing private-in printer insert the required parentheses.
This preserves grouping for arithmetic, exponentiation, and shift operators. Equal- and lower-precedence operators, such as `<`, `===`, and `&&`, continue to omit unnecessary parentheses. The correction applies to both the ordinary and source-map-enabled JavaScript printer builds and brings this path in line with the Rust codegen fix in #26383.
`packages/codegen` emits invalid TypeScript for abstract accessors with an explicit accessibility modifier. The JavaScript printer writes `abstract` before `public` or `protected`, but TypeScript requires accessibility to come first and reports TS1029 for the generated declaration.
For example, this valid input:
```ts
abstract class C {
public abstract accessor x: number;
protected abstract accessor y: string;
}
```
was printed as:
```ts
abstract class C {
abstract public accessor x: number;
abstract protected accessor y: string;
}
```
The printer now preserves the valid modifier order:
```ts
abstract class C {
public abstract accessor x: number;
protected abstract accessor y: string;
}
```
`printAccessorProperty` now emits accessibility before `abstract`, matching the neighboring method and property printers. The same ordering also handles declarations such as `protected abstract override accessor x: number` and applies to both the ordinary and source-map-enabled builds.
This brings the JavaScript printer in line with the Rust codegen correction in #26392. The change is confined to accessor modifier ordering; subsequent `static`, `override`, and `accessor` emission and source-map anchoring retain their existing behavior.
camc314