Announcing TypeScript 6.0

Overview

TypeScript 6.0 announced as the last release based on the current JavaScript codebase. It's the bridge to TypeScript 7.0, which uses a new Go-based native compiler.

What's New in TypeScript 6.0

1. Less Context-Sensitivity on this-less Functions

TypeScript 6.0 fixes inference for methods without explicit this usage:

// Before: error because consume's y was 'unknown'
callIt({
    consume(y) { return y.toFixed(); },
    produce(x: number) { return x * 2; },
});

// Now works - if 'this' is never used, function is not contextually sensitive

2. Subpath Imports Starting with #/

Now supports Node.js subpath imports with #/ prefix:

{
  "name": "my-package",
  "imports": {
    "#/*": "./dist/*"
  }
}

// Now works:
import * as utils from "#/utils.js";

3. Module Resolution Bundler + CommonJS

Now supports combining --moduleResolution bundler with --module commonjs.

Deprecations

• Import assertion syntax (import ... assert {...}) deprecated
• Extended to import() calls: import(..., { assert: {...}})

TypeScript 7.0 Preview

The new Go-based compiler offers:

• Native code speed
• Shared-memory multi-threading
• Try in VS Code: vscode marketplace
• Or npm: npm install @typescript/native-preview

Significance

TypeScript 6.0 marks the end of an era for the JavaScript-based compiler and the start of a new native era. The transition to Go represents a major architectural change for TypeScript.

Original Article