build: fix async private method token fusion; inlineChat: adopt native private fields

[jrieken]

Summary

Fix async private method token fusion in the private-to-property build rewrite, and adopt native ES private fields in the inlineChat module.

Session Context

Key decisions from the development session:

• Token fusion fix approach: When the character before # is an identifier character (e.g. async#run), the replacement is prefixed with a space (async $a instead of async$a). This is safe because an extra space in a non-minified position never changes semantics, and in minified code it's the minimal fix to prevent the $ from fusing with the preceding keyword.
• isIdentifierChar helper: Checks a-z, A-Z, 0-9, _, $ — the characters that can continue an identifier in JS. Placed outside convertPrivateFields as a module-level utility since it's pure and stateless.
• Test-first: The async fusion bug was first reproduced with failing tests, then fixed. Three test variants cover: minified async#method, minified static async#method, and non-minified async #method (which already had a space and passed before the fix).
• Build-time syntax check (from prior PR): The esbuild.transform() syntax check added in the prior PR is what caught this bug during the build — it works as intended.

Changes

Commit 1: build: fix async private method token fusion

• private-to-property.ts: When emitting a replacement for a PrivateIdentifier, check if the preceding character is an identifier char. If so, prepend a space to prevent token fusion (e.g. async#run → async $a not async$a).
• private-to-property.ts: Add isIdentifierChar() helper.
• test/private-to-property.test.ts: 3 new tests for async, static async, and readable async private methods.

Commit 2: inlineChat: adopt native ES private fields

• Convert 8 inlineChat files from private _field to #field pattern.

[Copilot]

Pull request overview

This PR addresses a build-time bug in the private-field rewrite (token fusion for minified async#method patterns) and modernizes the inline chat implementation by switching from TypeScript private _field members to native ES #private fields.

Changes:

• Fix convertPrivateFields to insert a separating space when a PrivateIdentifier follows an identifier character (prevents async$a token fusion).
• Add/extend unit tests covering async private method minified forms.
• Convert inline chat browser code to use native #private fields for state and injected services.

Show a summary per file

File	Description
build/next/private-to-property.ts	Prevents token fusion by conditionally prefixing replacements with a space based on preceding character.
build/next/test/private-to-property.test.ts	Adds tests intended to cover async/static-async private method minified cases.
src/vs/workbench/contrib/inlineChat/browser/inlineChatZoneWidget.ts	Migrates internal state/options/logging to native #private fields.
src/vs/workbench/contrib/inlineChat/browser/inlineChatWidget.ts	Migrates widget internals and injected services to #private fields.
src/vs/workbench/contrib/inlineChat/browser/inlineChatSessionServiceImpl.ts	Migrates service internals/events/session map to #private fields.
src/vs/workbench/contrib/inlineChat/browser/inlineChatOverlayWidget.ts	Migrates overlay widgets’ DOM/state/history interactions to #private fields.
src/vs/workbench/contrib/inlineChat/browser/inlineChatNotebook.ts	Migrates disposable store to #private field.
src/vs/workbench/contrib/inlineChat/browser/inlineChatHistoryService.ts	Migrates storage/history handling to #private fields/method.
src/vs/workbench/contrib/inlineChat/browser/inlineChatEditorAffordance.ts	Migrates widget state/editor refs to #private fields and methods.
src/vs/workbench/contrib/inlineChat/browser/inlineChatController.ts	Migrates controller state/services and internal helpers to #private fields/methods.

Copilot's findings

• Files reviewed: 10/10 changed files
• Comments generated: 1

[Copilot]

The “static async private method — no token fusion” test only checks that the transformed output parses via new Function(result.code). That can still pass even if async#init incorrectly fuses into an identifier (e.g. async$a) because the code remains syntactically valid, but Foo.$a won’t exist and/or await semantics won’t be preserved at runtime. Please extend this test to execute the transformed class (e.g. call Foo.go() and assert it resolves/returns as expected) so it actually detects token-fusion regressions for the static async case.

Suggested change

	test('static async private method — no token fusion', () => {
	const code = 'class Foo{static async#init(){await Promise.resolve()}static go(){return Foo.#init()}}';
	const result = convertPrivateFields(code, 'test.js');
	assert.doesNotThrow(() => new Function(result.code),
	'static async private method must produce valid JS, got:\n' + result.code);
	test('static async private method — no token fusion', async () => {
	const code = 'class Foo{static async#init(){return await Promise.resolve(1)}static go(){return Foo.#init()}}';
	const result = convertPrivateFields(code, 'test.js');
	assert.doesNotThrow(() => new Function(result.code),
	'static async private method must produce valid JS, got:\n' + result.code);
	const exec = new Function(`
	${result.code}
	return Foo.go();
	`);
	const value = await exec();
	assert.strictEqual(value, 1);