Large TS types cause type inference slowdown #166
Description
Hey! This isn't a big problem, but I'm putting the TS type checking speed diagnostics from Claude here in case some parts of the definitions can be simplified:
Biggest type producers:
1. sury — 63,313 types (you use it for schemas)
[...]
⏺ Found the issue. Looking at sury type definitions:
The type explosion comes from:
1. Recursive conditional types (UnknownToOutput, UnknownToInput) that traverse nested object structures:
export type UnknownToOutput<T> = T extends Schema<unknown>
? Output<T>
: T extends unknown[]
? { [K in keyof T]: UnknownToOutput<T[K]> } // recursive
: T extends { [k in keyof T]: unknown }
? Flatten<{
[k in keyof T as HasUndefined<...> extends true ? k : never]?: ...
} & { ... }> // conditional mapped type
: T;
2. Large discriminated union in Schema<Output, Input> — 14 variants (never, unknown, string, number, bigint, boolean, symbol, null, undefined, nan, function, instance, array, object, union)
3. Recursive tuple transformers (_RestToOutput, _RestToInput) that build up arrays type-by-type
Every time you write S.Output<typeof someSchema>, TypeScript:
- Infers the schema structure
- Traverses every field recursively
- Evaluates HasUndefined conditionals for each field
- Computes the mapped type with optional/required splits
With 138 usages of S.Output<> across your codebase and nested schemas, this compounds quickly → 63k types.
Seems this isn't very avoidable? If not, feel free to close!