Why TypeScript is moving to Go

The TypeScript team announced a native Go rewrite to achieve 7-10x faster compilation, dramatically reducing build times for large codebases. The Go compiler (codenamed 'Corsa') will be a full rewrite, not a port. TypeScript 6.0 serves as the transition release, deprecating everything that won't carry forward.

// Preparing for TypeScript 7.0 — the Go rewrite

// What's changing in TS 7 (native compiler):
// ✅ 10x faster type checking
// ✅ Same type system, same syntax
// ✅ tsc CLI remains the same

// What to do NOW:
// 1. Migrate off deprecated TS 5.x options
{
  "compilerOptions": {
    "target": "es2022",           // not "es5" (removed in TS 6)
    "module": "esnext",           // not "amd"/"umd" (removed)
    "moduleResolution": "bundler" // not "classic" (removed)
  }
}

// 2. Remove "ignoreDeprecations": "6.0" before TS 7
// 3. Run TS 6 in CI to catch new strict-by-default errors
// 4. Test with nightly: npm install typescript@next

What gets hard-removed in 7.0

Every option deprecated in TS 6.0 becomes a hard error in 7.0 with no escape hatch. This includes: target es3/es5, outFile, downlevelIteration, moduleResolution node/classic, module amd/umd/system/none, baseUrl as resolution root, esModuleInterop: false, allowSyntheticDefaultImports: false, alwaysStrict: false, module Foo {} namespace syntax, and import assertions (assert keyword).

How to prepare today

Run your tsconfig.json through the Migration Checker to identify all issues. Fix errors first (these are already broken in 6.0), then warnings (deprecated but escapable), then info items (no-ops to clean up). Use the "ignoreDeprecations": "6.0" escape hatch only as a temporary measure while you migrate.