This document outlines our focused tasks for TypeScript 4.9. It minimally indicates intent to investigate tasks or contribute to an implementation. Nothing is set in stone, but we will strive to complete these tasks in a reasonable timeframe.

gantt
    dateFormat  YYYY-MM-DD
    TypeScript 4.8 Stabilization Period : 2022-08-05, 2022-08-25
    TypeScript 4.9 Beta Development : 2022-08-05, 2022-09-16
    TypeScript 4.9 RC Development : 2022-09-16, 2022-10-28
    TypeScript 4.9 Stabilization Period : 2022-10-28, 2022-11-15
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Language and Compiler Features

• ECMAScript Decorators
• Contextually Typed And Compatible Operator
• lib.d.ts Updates
• Support .ts as a Module Specifier for Bundler/Loader Scenarios
• Investigate Fine-Granularity Module Resolution Options
• Investigate Per-File Settings
• Make @types/web Versionable
• Investigate --isolatedDeclaration Emit Mode

Editor Productivity

• Switch to FsEvents for File-Watching by Default
• Virtual File System Support in TSServer
• Investigate Cancellation in Browser Contexts
• Prototype Automatic Type Acquisition in Web Contexts
• Investigate TS Server Plugins on the Web
• High Confidence JavaScript Diagnostics in Classes
• Provide Walkthroughs in Visual Studio Code Welcome View
• Easy Run/Debug for Loose TypeScript Files

Performance

• Investigate Module Resolution Caching in .tsbuildinfo Files
• Investigate Tooling for JIT Deoptimizations
• Investigate Outstanding Performance Issues
• Enrich TS Server Tracepoints

Infrastructure

• Enable strictFunctionTypes on TypeScript Codebase
• Determining Module Migration and Shipping Strategy
• Rewrite TSServer Crawler
• TSServer Performance Testing Infrastructure

Website

• Accessibility Improvements
• Make Onboarding and Cross-Platform Installation Smoother