Type System Patterns

7/6/2025 · 3 min

1. Subtractive inference

Precompute record of event → payload to avoid repeated conditional expansion.

2. Generated literal surfaces

Build step emits literal unions (networks, events). Favor ergonomics first; optimize size after stability.

3. Escape hatch

Use widening patterns (string & {}) for forward compatibility without losing autocomplete.

4. Template literal transforms

Recursive template literal mapping (A.B.C → A_B_C) producing stable identifiers while preserving original runtime values.

5. Decision checklist

□ Can we precompute?
□ Replace repeated conditional access with indexed map lookup
□ Defer size optimization until adoption data exists
□ Provide an escape path for unknown future values

Subtractive type design: precompute, map, and escape—repeat.

See also

• Type-safe webhook events
• When TypeScript unions get too big