The native port of the TypeScript compiler also has made significant progress, with TypeScript 7.0 type checking nearly complete. A frequent question is whether it is “safe” to use TypeScript 7.0 to validate a build, Rosenwasser said, or in other words, does the TypeScript 7.0 compiler reliably find the same errors that TypeScript 5.9 does? The answer is yes, he said. For context, there have been around 20,000 compiler test cases, of which about 6,000 produce at least one error in TypeScript 6.0. In all but 74 cases, TypeScript 7.0 also produces at least one error. Developers can confidently use TypeScript 7.0 today to type-check a project for errors, Rosenwasser said. Beyond single-pass/single-project type checking, the command-line compiler also has reached major parity. Features such as --incremental, project reference support, and --build mode are all ported over and working.
TypeScript 7.0 will remove behaviors and flags planned for deprecation in TypeScript 6.0. A list of upcoming deprecations in TypeScript 6.0 can be seen in the issue tracker. For emit, --watch, and API capabilities, the JavaScript pipeline is not entirely complete. Developers who do not need JavaScript emit from TypeScript, running tsgo for a build will work fine, Rosenwasser said. Also, TypeScript 7.0 (Corsa) will not support the existing Strada API. The Corsa API is still a work in progress.
With TypeScript 6.0, there is no intention to produce a TypeScript 6.1 release, although there may be patch releases for TypeScript 6. “You can think of TypeScript 6.0 as a ‘bridge’ release between the TypeScript 5.9 line and 7.0,” Rosenwasser said. “6.0 will deprecate features to align with 7.0, and will be highly compatible in terms of type-checking behavior.” The intent is to ensure that TypeScript 6.0 and TypeScript 7.0 are as compatible as possible.
