…ering (#23516)

## What

Two zero-capacity arena `Vec`s in the TypeScript transformer were filled
in known-length loops and grew via reallocation. Pre-size them —
mirroring the JSX-props pre-size in #23466:

- **`transform_ts_enum_members`**: emits exactly `members.len() + 1`
statements (one per member + the final `return`) →
`vec_with_capacity(members.len() + 1)` (an **exact** capacity).
- **TS namespace `enter_program`**: rebuilds the program body; pre-size
to `program.body.len()` (an estimate — most statements pass through
1:1).

## Δ — fewer reallocations on TS fixtures

`allocs_transformer.snap`, reallocation count:

| fixture | before | after |
| --- | --- | --- |
| checker.ts | 64 | **5** |
| kitchen-sink.tsx | 304 | **280** |
| App.tsx | 25 | **17** |
| binder.ts | 6 | **0** |

(allocation **count** and **bytes** are unchanged — this removes the
intermediate growth reallocations.)

## Why it is behavior-preserving

Capacity-only: `vec_with_capacity` differs from `vec` solely in initial
capacity; element type, push order, and contents are identical, so the
produced AST is byte-identical. `oxc_transformer` tests pass.

Prepared with AI assistance.

### 💥 BREAKING CHANGES

- 7a76cd3 estree: [**BREAKING**] Make whether to include TS fields a
runtime option (#23574) (overlookmotel)
- e7b6b68 estree: [**BREAKING**] `ESTree` config use methods not consts
(#23573) (overlookmotel)

### 🚀 Features

- 556cc6d data_structures: Add `CodeBuffer::as_str` method (#23571)
(overlookmotel)
- 38c4b06 parser: Add friendly error for adjacent JSX elements (#23378)
(sapphi-red)
- 53509a8 minifier: Treeshake pure typed arrays and Set/Map array
literals (#23469) (Dunqing)
- 09762d9 minifier: Inline const value for read-only vars (#22593)
(Dunqing)

### 🐛 Bug Fixes

- 20375f9 react_compiler: Keep imports referenced only by a computed key
(#23586) (Boshen)
- 31bfd9b minifier: Keep Object introspection calls on a possible Proxy
(#23483) (Dunqing)
- 837a395 parser: Treat a line comment after ':' as leading, not
trailing (#23515) (Dunqing)
- e409fe0 minifier: Keep `new Map`/`WeakSet`/`WeakMap` with a string
argument (#23470) (Dunqing)
- ae02b4e ci/parser: Use `minimal` for vitest reporter (#23457)
(camc314)

### ⚡ Performance

- cf24329 mangler: Compile slot sort once instead of per CAPACITY
(#23577) (Boshen)
- 4058a6a parser: Reduce code bloat from verify_modifiers
monomorphization (#23576) (Boshen)
- 053b0c1 estree: Remove pointless `mem::take` (#23572) (overlookmotel)
- dfb52b6 transformer: Pre-size statement vecs in TS enum & namespace
lowering (#23516) (Yunfei He)
- 970e09a minifier: Compute template-literal inline checks in a single
pass (#23467) (Yunfei He)
- 3170c0e semantic,mangler,minifier: Fix `Semantic::stats` node count
and reuse stats in mangler builds (#23352) (Boshen)
- d1fa6e0 minifier: Evaluate ternary branches once in
minimize_conditional_expression (#23479) (Yunfei He)
- 3fa8051 transformer: Pre-size JSX props vec to attribute count
(#23466) (Yunfei He)
- 488b382 react_compiler: Borrow binding names in prefilter instead of
allocating (#23471) (Yunfei He)
- bcb3894 minifier: Incremental scoping refresh, delete
LiveUsageCollector (#23197) (Dunqing)

### 📚 Documentation

- f68641e data_structures: Improve docs on safety contract (#23575)
(overlookmotel)

Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

## Memory reduction: fewer arena reallocations on JSX

`transform_jsx` built the `React.createElement` / jsx props object in a
**zero-capacity** arena vec
(`ctx.ast.vec()`), regrowing it (4 → 8 → 16 …) as it pushed one property
per attribute. The attribute
count is already known, so pre-sizing the vec to it removes those
regrowths — mirroring `arguments`,
pre-sized a few lines above, and the same pattern as #9915.

Measured with `cargo allocs` (`TestFiles::complicated`). **Arena
reallocations drop on every JSX file;
nothing else changes** (system allocs and the arena-alloc count are
essentially flat):

| file | arena reallocs: before → after | **reduction** |
| --- | --- | --- |
| App.tsx | 77 → 25 | **−52 (−68%)** |
| kitchen-sink.tsx | 517 → 304 | **−213 (−41%)** |
| RadixUIAdoptionSection.jsx | 24 → 13 | **−11 (−46%)** |

Each eliminated realloc is a buffer grow + memcpy of the existing
elements, so this is real
work removed on the JSX hot path, not just bytes.

<details><summary>Raw <code>allocs_transformer.snap</code> diff (updated
in this PR)</summary>

```diff
-App.tsx                    | 415.34 kB      ||             25 |              2 ||            719 |             77
+App.tsx                    | 415.34 kB      ||             25 |              2 ||            719 |             25
-RadixUIAdoptionSection.jsx | 2.52 kB        ||             21 |              2 ||            259 |             24
+RadixUIAdoptionSection.jsx | 2.52 kB        ||             21 |              2 ||            259 |             13
-kitchen-sink.tsx           | 732.90 kB      ||            184 |              3 ||           6689 |            517
+kitchen-sink.tsx           | 732.90 kB      ||            184 |              3 ||           6690 |            304
```

(Non-JSX files unchanged. The lone `+1` arena alloc on kitchen-sink is
an eager 1-slot allocation for
a rare element whose attributes are all filtered out — negligible
against −213 reallocs.)

</details>

## Change

```rust
let mut properties =
    ctx.ast.vec_with_capacity(opening_element.as_ref().map_or(0, |e| e.attributes.len()));
```

Capacity-only: the vec's contents, push order, and emitted output are
unchanged — only the initial
allocation differs. CodSpeed (instructions) may pick up the saved
memcpys on JSX-heavy input, but this
is framed as a memory/allocation win.

## Behavior-preserving

`cargo test -p oxc_transformer` passes. The change is a capacity hint
and cannot alter the produced AST.

---

Prepared with AI assistance.

Co-authored-by: Cameron <cameron.clark@hey.com>

…ering (#23516)

## What

Two zero-capacity arena `Vec`s in the TypeScript transformer were filled
in known-length loops and grew via reallocation. Pre-size them —
mirroring the JSX-props pre-size in #23466:

- **`transform_ts_enum_members`**: emits exactly `members.len() + 1`
statements (one per member + the final `return`) →
`vec_with_capacity(members.len() + 1)` (an **exact** capacity).
- **TS namespace `enter_program`**: rebuilds the program body; pre-size
to `program.body.len()` (an estimate — most statements pass through
1:1).

## Δ — fewer reallocations on TS fixtures

`allocs_transformer.snap`, reallocation count:

| fixture | before | after |
| --- | --- | --- |
| checker.ts | 64 | **5** |
| kitchen-sink.tsx | 304 | **280** |
| App.tsx | 25 | **17** |
| binder.ts | 6 | **0** |

(allocation **count** and **bytes** are unchanged — this removes the
intermediate growth reallocations.)

## Why it is behavior-preserving

Capacity-only: `vec_with_capacity` differs from `vec` solely in initial
capacity; element type, push order, and contents are identical, so the
produced AST is byte-identical. `oxc_transformer` tests pass.

Prepared with AI assistance.

### 💥 BREAKING CHANGES

- 7a76cd3 estree: [**BREAKING**] Make whether to include TS fields a
runtime option (#23574) (overlookmotel)
- e7b6b68 estree: [**BREAKING**] `ESTree` config use methods not consts
(#23573) (overlookmotel)

### 🚀 Features

- 556cc6d data_structures: Add `CodeBuffer::as_str` method (#23571)
(overlookmotel)
- 38c4b06 parser: Add friendly error for adjacent JSX elements (#23378)
(sapphi-red)
- 53509a8 minifier: Treeshake pure typed arrays and Set/Map array
literals (#23469) (Dunqing)
- 09762d9 minifier: Inline const value for read-only vars (#22593)
(Dunqing)

### 🐛 Bug Fixes

- 20375f9 react_compiler: Keep imports referenced only by a computed key
(#23586) (Boshen)
- 31bfd9b minifier: Keep Object introspection calls on a possible Proxy
(#23483) (Dunqing)
- 837a395 parser: Treat a line comment after ':' as leading, not
trailing (#23515) (Dunqing)
- e409fe0 minifier: Keep `new Map`/`WeakSet`/`WeakMap` with a string
argument (#23470) (Dunqing)
- ae02b4e ci/parser: Use `minimal` for vitest reporter (#23457)
(camc314)

### ⚡ Performance

- cf24329 mangler: Compile slot sort once instead of per CAPACITY
(#23577) (Boshen)
- 4058a6a parser: Reduce code bloat from verify_modifiers
monomorphization (#23576) (Boshen)
- 053b0c1 estree: Remove pointless `mem::take` (#23572) (overlookmotel)
- dfb52b6 transformer: Pre-size statement vecs in TS enum & namespace
lowering (#23516) (Yunfei He)
- 970e09a minifier: Compute template-literal inline checks in a single
pass (#23467) (Yunfei He)
- 3170c0e semantic,mangler,minifier: Fix `Semantic::stats` node count
and reuse stats in mangler builds (#23352) (Boshen)
- d1fa6e0 minifier: Evaluate ternary branches once in
minimize_conditional_expression (#23479) (Yunfei He)
- 3fa8051 transformer: Pre-size JSX props vec to attribute count
(#23466) (Yunfei He)
- 488b382 react_compiler: Borrow binding names in prefilter instead of
allocating (#23471) (Yunfei He)
- bcb3894 minifier: Incremental scoping refresh, delete
LiveUsageCollector (#23197) (Dunqing)

### 📚 Documentation

- f68641e data_structures: Improve docs on safety contract (#23575)
(overlookmotel)

Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>