TypeScript 6.0, the upcoming major update to Microsoft’s popular strongly typed JavaScript variant, has reached the release candidate (RC) stage. This version introduces several notable changes, including improved type checking for function expressions in generic calls. The RC is a step towards the full release, which is scheduled for March 17, after originally being expected earlier in the month.

What’s New in TypeScript 6.0 RC

The latest RC version adds enhanced support for type checking in generic function calls, particularly those within JSX expressions. This change aims to align TypeScript 6.0 more closely with the upcoming TypeScript 7.0, which will be based on the Go programming language for better performance. Developers can install the RC through NPM with the command npm install -D typescript@rc.

One of the key updates is an adjustment that helps catch more bugs related to generic calls, although it might require developers to specify explicit type arguments more often. Additionally, Microsoft has extended the deprecation of import assertion syntax. Now, syntax like import ... assert {...} is deprecated not only in static import statements but also in dynamic import calls such as import(..., { assert: {...} }).

Other Improvements and Changes

TypeScript 6.0 updates the DOM types to reflect the latest web standards, including improvements to the Temporal API. The release also introduces the RegExp.escape function, which helps escape special characters in regular expressions, like *, ?, and +. This feature is now part of the ECMAScript stage 4 proposal and is available in the es2025 library.

Further, the contents of declaration files such as lib.dom.iterable.d.ts and lib.dom.asynciterable.d.ts are now included within lib.dom.d.ts. This makes it easier for developers to specify what global declarations their runtime environment supports through TypeScript’s lib option. The release also marks the deprecation of the asserts syntax, which was proposed as part of the import assertions feature but has since been replaced by the import attributes proposal, using the with keyword instead.

Microsoft expects TypeScript 7.0 to follow soon after, aiming to maintain continuity and provide a faster feedback loop for developers during migration. Overall, TypeScript 6.0 RC introduces meaningful improvements that will help developers write more reliable code while preparing for the next major version based on a new language foundation.

Inspired by

• https://www.infoworld.com/article/4143186/typescript-6-0-reaches-release-candidate-stage.html

Sources

• microsoft.com
• github.com
• github.com