Skip to content

Support multiple super-traits in type system #8

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 3 commits into
base: master
Choose a base branch
from
Open

Support multiple super-traits in type system #8

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
576196b
attempt at fixing multiple super-traits
int0h Aug 4, 2025
194fc57
removed extra exports
int0h Aug 4, 2025
4e1e8f9
export Derived<T> type
int0h Aug 4, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
52 changes: 32 additions & 20 deletions src/traits.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,33 @@ export type Trait<
superTraits: ST
}

type ResolveTraitLike<T extends Trait | TypeFactory<Trait>> =
T extends TypeFactory<Trait>
? ExtractFactory<ReturnType<T>>
: T extends Trait
? ExtractFactory<T>
: unknown;

type Combine<T extends any[]> =
T extends [infer Head, ...infer Tail]
? Head & Combine<Tail>
: {};

type MapClassesToPrototypes<T extends Array<(new () => any) & {prototype: any}>> = {
[K in keyof T]: T[K]['prototype'];
}

type MapClassesToInstances<T extends Array<(new () => any) & {prototype: any}>> = {
[K in keyof T]: InstanceType<T[K]>;
}

type CombineClasses<T extends Array<(new () => any) & {prototype: any}>> =
(new () => Combine<MapClassesToInstances<T>>) & {prototype: Combine<MapClassesToPrototypes<T>>};

type ResolveTraitLikeArray<T extends Array<Trait | TypeFactory<Trait>>> = CombineClasses<{
[K in keyof T]: ResolveTraitLike<T[K]>;
}>;

/* API: generate trait (regular variant) */
/* eslint no-redeclare: off */
export function trait<
Expand All @@ -110,28 +137,13 @@ export function trait<
/* API: generate trait (super-trait variant) */
export function trait<
const ST extends (Trait | TypeFactory<Trait>)[],
T extends ConsFactory<Cons,
ST extends [ infer First, ...infer Rest ] ? (
First extends TypeFactory<Trait> ? ExtractFactory<ReturnType<First>> :
First extends Trait ? ExtractFactory<First> :
any
) : any
>
T extends ConsFactory<Cons, ResolveTraitLikeArray<ST>>
> (superTraits: ST, factory: T): Trait<T, ST>

/* API: generate trait (technical implementation) */
export function trait<
const ST extends (Trait | TypeFactory<Trait>)[],
T extends ConsFactory<Cons,
ST extends [ infer First, ...infer Rest ] ? (
First extends TypeFactory<Trait> ? ExtractFactory<ReturnType<First>> :
First extends Trait ? ExtractFactory<First> :
any
) : any
>
> (...args: any[]): Trait<T, ST> {
const factory: T = (args.length === 2 ? args[1] : args[0])
const superTraits: ST = (args.length === 2 ? args[0] : undefined)
export function trait(...args: any[]): Trait<any, any> {
const factory: ConsFactory<any, any> = (args.length === 2 ? args[1] : args[0])
const superTraits: (Trait | TypeFactory<Trait>)[] = (args.length === 2 ? args[0] : undefined)
return {
id: crc32(factory.toString()),
symbol: Symbol("trait"),
Expand Down Expand Up @@ -405,7 +417,7 @@ type DerivedType<T extends Trait> =
InstanceType<ExtractFactory<T>>

/* internal type: implements trait type or trait type factory */
type Derived<T extends (Trait | TypeFactory<Trait> | Cons)> =
export type Derived<T extends (Trait | TypeFactory<Trait> | Cons)> =
T extends TypeFactory<Trait> ? DerivedType<ReturnType<T>> :
T extends Trait ? DerivedType<T> :
T extends Cons ? T :
Expand Down