Microsoft said several new types have been renamed since the beta. Previously, TypeScript provided a single type called BuiltinInterator to describe every value backed by Iterator.prototype. This type has been renamed IteratorObject in the RC, and has been given a different set of type parameters. It also adds several subtypes such as ArrayIterator and MapIterator.

Also in the RC, a new flag called --stopOnBuildErrors has been added for --build mode that stops builds if a project builds with any errors. New editor functionality also has been added including direct support for commit characters and exclude patterns for auto-imports.

Prior to the RC, the TypeScript 5.6 beta introduced a variety of changes. For disallowed nullish and truthy checks, the compiler now errors when it can syntactically determine that a truthy or nullish check will always evaluate in a specific way. Microsoft said “many, many bugs” could be caught this way. Some expressions still are allowed even if truthy or nullish. Specifically, true, false, 0, and 1 are all still allowed despite always being truthy or falsy.