mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-11-03 07:54:40 +08:00
Chris Tate
d99fc851e6
In a JavaScript file, `const m = new Map()`, `new Set()` and `[]` type as Map<any, any>, Set<any> and any[], so every use lowered to the checked-dynamic collection operations: boxed keys and values, generic method dispatch, and dynamic arithmetic on what they returned. js-collection-types.ts proves types for such bindings from their uses. A `const` qualifies when every reference is a direct use of the collection: - for a Map: get/has/delete/clear, size, and set as a statement; - for a Set: has/delete/clear, size, and add as a statement; - for an array: push/pop/shift/at/includes/indexOf/join and length. The value then never leaves the binding. Its key, value or element type is the one primitive (string, number or boolean) of every expression the program writes. That is found by a fixed point that types `m.get(k) ?? d`, arithmetic, comparisons and constants defined from them, and it requires lookups of the same type. Any other reference (passing, returning, storing, exporting, iterating, inspecting, an optional call), a direct `eval` in the file, or any doubt keeps the binding untyped. A proven binding answers the lowerer's typeOf with a carrier type declared in scriptc-overrides.d.ts, which only the lowering program includes. `new Map()` and `new Set()` adopt it, so the binding lowers as the typed Map<K, V>, Set<K> or T[], as a JSDoc @type would make it. 7985 covers the typed cases and every refusal.
94 lines
4.3 KiB
TypeScript
94 lines
4.3 KiB
TypeScript
/* scriptc's divergence and precision overrides — interface merges that
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* re-type a handful of standard-library members to scriptc's documented
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* runtime behavior. Merged interfaces resolve overloads later-declaration-
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* first, so these win at call sites that match them; call forms only the
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* lib signatures accept still typecheck and are fenced by the lowerer.
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*
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* This file is part of the LOWERING program only. Preflight's second-chance
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* pass (checkPreflight) rebuilds the program WITHOUT it — the project's own
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* type world — so a program that typechecks under its own tsc is never
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* rejected over an override-manufactured error; the affected sites meet the
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* lowerer's honest fences instead (SC1100's checked-cast family for
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* JSON.parse results, the executor fences for Promise shapes). The
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* primitives every world needs (comptime, setTimeout) live
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* in scriptc.d.ts, which ships to BOTH programs. */
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interface String {
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at(index: number): string;
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}
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interface ObjectConstructor {
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values<T extends object>(o: T): Array<keyof T extends never ? unknown : T[keyof T]>;
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entries<T extends object>(o: T): Array<[string, keyof T extends never ? unknown : T[keyof T]]>;
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}
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interface JSON {
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parse(text: string): unknown;
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parse(text: string, reviver: (this: unknown, key: string, value: unknown) => unknown): unknown;
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stringify(value: unknown): string;
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stringify(
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value: unknown,
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replacer: (this: unknown, key: string, value: unknown) => unknown,
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space?: string | number,
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): string | undefined;
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}
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/* The supported Promise construction shape: an executor whose resolve takes
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* the plain value. Preferred over the lib signature at inference time, so
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* `new Promise<T>((resolve) => ...)` types resolve as `(value: T) => void`
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* — no PromiseLike union. The reject parameter is a real closure rejecting
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* the promise; its reason is pinned to Error (the lib says `reason?: any`)
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* because rejection payloads ride the same representation as thrown values
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* and the idiomatic reason IS an Error — reject(nonError) and bare
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* reject() typecheck only in the project world and meet the lowerer's
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* honest coercion fences instead. First settle wins, exactly JS: a reject
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* after resolve (or a second reject) is a no-op, and an executor throw
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* after any settle is swallowed. Executors that use the lib signature's
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* other extras (resolving with a thenable) still typecheck and fail
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* lowering on their types. */
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interface PromiseConstructor {
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new <T>(
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executor: (resolve: (value: T) => void, reject: (reason: Error) => void) => void,
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): Promise<T>;
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/* ES2024's Promise.withResolvers, in the executor's own scriptc shape:
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* resolve takes the plain value (no PromiseLike union; the conditional
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* collapses Promise<void>'s resolve to () => void so the record's
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* field types map exactly), reject is the executor's Error-pinned
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* rejection closure. The lib's own declaration would otherwise be
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* unrepresentable field-by-field. */
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withResolvers<T>(): {
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promise: Promise<T>;
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// `0 extends 1 & T` detects any (untyped JS: Promise.withResolvers()
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// infers it) — its settled value rides the dyn arm like unknown's,
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// so resolve takes one unknown; a naked conditional over any would
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// otherwise union BOTH branches, which no field can map.
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resolve: 0 extends 1 & T
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? (value: unknown) => void
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: [T] extends [void]
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? () => void
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: (value: T) => void;
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reject: (reason: Error) => void;
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};
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}
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/* Carriers of the types the lowerer gives untyped JavaScript collections
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* whose uses prove them (js-collection-types.ts). Nothing reads them at run
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* time. */
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declare namespace __scriptcInferredCollections {
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const map_string_string: Map<string, string>;
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const map_string_number: Map<string, number>;
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const map_string_boolean: Map<string, boolean>;
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const map_number_string: Map<number, string>;
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const map_number_number: Map<number, number>;
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const map_number_boolean: Map<number, boolean>;
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const map_boolean_string: Map<boolean, string>;
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const map_boolean_number: Map<boolean, number>;
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const map_boolean_boolean: Map<boolean, boolean>;
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const set_string: Set<string>;
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const set_number: Set<number>;
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const set_boolean: Set<boolean>;
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const array_string: string[];
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const array_number: number[];
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const array_boolean: boolean[];
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}
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