prefer-typescript-7-native-compiler

TypeScript version evidence uses the root lockfile dependency where available, and ignores unrelated aliases and unresolved package protocols.

Why it matters

TypeScript 7 is a native Go port of the compiler (Project Corsa). It keeps the type-checking logic of TypeScript 6.0 while replacing the Node.js-based tsc with a native binary that uses shared-memory parallelism.

Microsoft reports on production-scale codebases:

7x-12x faster full builds (for example VS Code 125.7s -> 10.6s)
up to 30x faster type checking on medium-to-large projects
roughly 3x lower memory use
faster editor startup and first-error latency through the native language service

The speed comes from native execution and parallelism, not from changed checking rules, so moving to TypeScript 7 is mostly a compiler swap.

What it flags

Flags a repository whose package.json depends on TypeScript 5.x or 6.x. The rule reads the TypeScript version from repository signals derived from package.json.

Repositories on TypeScript 4.x or earlier, already on TypeScript 7.x or later, or with no detectable typescript dependency, are not flagged.

This rule is independent from prefer-typescript-5-performance-milestone, which recommends short-term 5.x milestones. A repository on TypeScript 5.x can receive both findings: one for the next 5.x step and one for the larger 7.x jump.

Suggested action

Confirm the codebase compiles cleanly under TypeScript 6.0 semantics first (stableTypeOrdering on, no ignoreDeprecations). The TypeScript team expects code that compiles cleanly with 6.0 to compile identically under 7.0.
Switch the typescript dependency to 7.x. The compiler binary is tsc.
TypeScript 7.0 does not ship a stable programmatic API (planned for 7.1). If a tool such as typescript-eslint needs the API, run TypeScript 6 and 7 side by side instead of replacing the package outright.
In CI, tune --checkers and --builders to the runner. These are not auto-detected: --checkers defaults to a fixed 4 and --builders controls parallel project-reference builds under --build. Raise them on larger runners and lower them on small or memory-limited runners; use --singleThreaded to disable parallelization entirely. Parsing and emitting parallelize automatically, but type-checking only scales when these flags are set.

Verification

Compare full type-check and build wall-clock time before and after the upgrade.
Compare peak memory during type checking.
Check editor or language-service error latency if it matters for local development.
Run the existing test suite and type-check in CI to confirm behavioral parity.

What the scanner does