Upgrade TypeScript 5.9 → 7.0 beta (native Go compiler)

[Simply007]

Summary

Upgrades the TypeScript compiler from 5.9.3 to 7.0 beta (@typescript/native-preview), which rewrites the compiler in Go and delivers ~8× faster build times. All existing type-level code, type tests, and tooling continue to work without modification to the core arithmetic types.

Also adds a full comparison of the plain-JS calculator vs the type-level calculator, covering both compile-time overhead and runtime parity.

Build-speed comparison

Measured on this project (NodeNext ESM, strict mode, macOS Apple Silicon):

Scenario	tsc 5.9.3	tsgo 7.0-dev	Speedup
Type-check (--noEmit)	~0.285 s	~0.035 s	~8×
Full build (emit JS + .d.ts)	~0.333 s	~0.043 s	~7.7×

See TYPESCRIPT_7_UPGRADE.md for raw numbers and full change analysis.

JS vs type-level calculator comparison (npm run compare)

	Plain JS	Type-level
Return type of add(55, 67)	number	122 (exact literal)
Build-time cost	trivial	small (scales with digit count / operand magnitude)
Runtime cost	a + b	a + b — identical (cast erased at emit)
Recursion limit	none	Mul first operand ≤ 999

See CALCULATOR_COMPARISON.md for full tables and analysis.

Changes

package.json

• typescript → npm:@typescript/native-preview@^7.0.0-dev.20260421.2 (Go-native compiler, tsgo binary)
• Add typescript-api → npm:typescript@^5.9 alias — kept for dev tools that use the TS programmatic JS API (not yet available in TS 7.0, planned for 7.1)
• Build script: tsc → tsgo
• Add compare script: npx tsx tools/compare-calculator.ts

src/index.ts

• Remove unused import { SourceMap } from 'node:module'

tools/inspect-types.ts · tools/benchmark-sum.ts · tools/compare-calculator.ts (new)

• Tool imports updated to typescript-api; new compare tool added

tsconfig.json — no changes needed

Test plan

• npm run build — compiles cleanly with tsgo
• npm run test:types — all tsd type assertions pass
• npm run inspect:sum — Sum<1234,5678> = 6912 ✓
• npm run benchmark — all Sum cases correct; Mul limit confirmed at 999
• npm run compare — comparison tool runs end-to-end cleanly

TODO before merging (waiting on stable TS 7.0 release)

• Replace npm:@typescript/native-preview@^7.0.0-dev.* with typescript@^7.0.0 once published
• Confirm binary name in stable release (tsgo vs tsc) and update build script
• Remove typescript-api alias and revert tool imports once TS 7.1 ships stable programmatic API
• Re-run benchmarks and update TYPESCRIPT_7_UPGRADE.md + CALCULATOR_COMPARISON.md with stable numbers
• Verify tsd@^0.31.0, tsx@^4.7.0, and @types/node@^25 work with stable TS 7.0
• Delete the TODO section from TYPESCRIPT_7_UPGRADE.md

Full checklist with context: TYPESCRIPT_7_UPGRADE.md#todo

Known limitation

npm run inspect / npm run benchmark / npm run compare use the TS 5.9 programmatic API (typescript-api alias). TS 7.0 has no stable JS API until 7.1. The TypeScript version: 5.9.3 line in tool output is expected.