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Merged
Anders Hejlsberg (ahejlsberg) merged 2 commits into from
Oct 3, 2026
Merged

Ensure stable ordering in getInferTypeParameters result #64621

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e038e3f
Ensure stable ordering in getInferTypeParameters result
ahejlsberg Oct 3, 2026
dd54f62
Add regression test
ahejlsberg Oct 3, 2026
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1 change: 1 addition & 0 deletions tsc/internal/checker/checker.go
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Expand Up @@ -24268,6 +24268,7 @@ func (c *Checker) getInferTypeParameters(node *ast.Node) []*Type {
result = append(result, c.getDeclaredTypeOfSymbol(symbol))
}
}
slices.SortFunc(result, CompareTypes)
return result
}

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54 changes: 54 additions & 0 deletions tsc/testdata/baselines/reference/compiler/stableTypeMapperOrdering.js
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//// [tests/cases/compiler/stableTypeMapperOrdering.ts] ////

//// [stableTypeMapperOrdering.ts]
// https://github.com/microsoft/TypeScript/issues/64589

interface Endpoint<Name, Params, Middleware, Services> {
readonly name: Name;
readonly params: Params;
readonly middleware: Middleware;
readonly services: Services;
}

type Same<A, R> = R;

type AddMiddleware<E, I> =
E extends Endpoint<infer N, infer P, infer M, infer S>
? Endpoint<N, P, M | I, Same<I, S>>
: never;

interface Group<Endpoints> {
add<N extends string, P = never>(
name: N,
params?: P,
): Group<Endpoints | Endpoint<N, P, never, never>>;
middleware<I>(id: I): Group<AddMiddleware<Endpoints, I>>;
}

declare const group: Group<never>;

export const result = group.add("a", { id: "" }).add("c").middleware("m" as const);


//// [stableTypeMapperOrdering.js]
// https://github.com/microsoft/TypeScript/issues/64589
export const result = group.add("a", { id: "" }).add("c").middleware("m");


//// [stableTypeMapperOrdering.d.ts]
interface Endpoint<Name, Params, Middleware, Services> {
readonly name: Name;
readonly params: Params;
readonly middleware: Middleware;
readonly services: Services;
}
type Same<A, R> = R;
type AddMiddleware<E, I> = E extends Endpoint<infer N, infer P, infer M, infer S> ? Endpoint<N, P, M | I, Same<I, S>> : never;
interface Group<Endpoints> {
add<N extends string, P = never>(name: N, params?: P): Group<Endpoints | Endpoint<N, P, never, never>>;
middleware<I>(id: I): Group<AddMiddleware<Endpoints, I>>;
}
export declare const result: Group<Endpoint<"a", {
id: string;
}, "m", never> | Endpoint<"c", never, "m", never>>;
export {};
111 changes: 111 additions & 0 deletions tsc/testdata/baselines/reference/compiler/stableTypeMapperOrdering.symbols
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//// [tests/cases/compiler/stableTypeMapperOrdering.ts] ////

=== stableTypeMapperOrdering.ts ===
// https://github.com/microsoft/TypeScript/issues/64589

interface Endpoint<Name, Params, Middleware, Services> {
>Endpoint : Symbol(Endpoint, Decl(stableTypeMapperOrdering.ts, 0, 0))
>Name : Symbol(Name, Decl(stableTypeMapperOrdering.ts, 2, 19))
>Params : Symbol(Params, Decl(stableTypeMapperOrdering.ts, 2, 24))
>Middleware : Symbol(Middleware, Decl(stableTypeMapperOrdering.ts, 2, 32))
>Services : Symbol(Services, Decl(stableTypeMapperOrdering.ts, 2, 44))

readonly name: Name;
>name : Symbol(Endpoint.name, Decl(stableTypeMapperOrdering.ts, 2, 56))
>Name : Symbol(Name, Decl(stableTypeMapperOrdering.ts, 2, 19))

readonly params: Params;
>params : Symbol(Endpoint.params, Decl(stableTypeMapperOrdering.ts, 3, 22))
>Params : Symbol(Params, Decl(stableTypeMapperOrdering.ts, 2, 24))

readonly middleware: Middleware;
>middleware : Symbol(Endpoint.middleware, Decl(stableTypeMapperOrdering.ts, 4, 26))
>Middleware : Symbol(Middleware, Decl(stableTypeMapperOrdering.ts, 2, 32))

readonly services: Services;
>services : Symbol(Endpoint.services, Decl(stableTypeMapperOrdering.ts, 5, 34))
>Services : Symbol(Services, Decl(stableTypeMapperOrdering.ts, 2, 44))
}

type Same<A, R> = R;
>Same : Symbol(Same, Decl(stableTypeMapperOrdering.ts, 7, 1))
>A : Symbol(A, Decl(stableTypeMapperOrdering.ts, 9, 10))
>R : Symbol(R, Decl(stableTypeMapperOrdering.ts, 9, 12))
>R : Symbol(R, Decl(stableTypeMapperOrdering.ts, 9, 12))

type AddMiddleware<E, I> =
>AddMiddleware : Symbol(AddMiddleware, Decl(stableTypeMapperOrdering.ts, 9, 20))
>E : Symbol(E, Decl(stableTypeMapperOrdering.ts, 11, 19))
>I : Symbol(I, Decl(stableTypeMapperOrdering.ts, 11, 21))

E extends Endpoint<infer N, infer P, infer M, infer S>
>E : Symbol(E, Decl(stableTypeMapperOrdering.ts, 11, 19))
>Endpoint : Symbol(Endpoint, Decl(stableTypeMapperOrdering.ts, 0, 0))
>N : Symbol(N, Decl(stableTypeMapperOrdering.ts, 12, 26))
>P : Symbol(P, Decl(stableTypeMapperOrdering.ts, 12, 35))
>M : Symbol(M, Decl(stableTypeMapperOrdering.ts, 12, 44))
>S : Symbol(S, Decl(stableTypeMapperOrdering.ts, 12, 53))

? Endpoint<N, P, M | I, Same<I, S>>
>Endpoint : Symbol(Endpoint, Decl(stableTypeMapperOrdering.ts, 0, 0))
>N : Symbol(N, Decl(stableTypeMapperOrdering.ts, 12, 26))
>P : Symbol(P, Decl(stableTypeMapperOrdering.ts, 12, 35))
>M : Symbol(M, Decl(stableTypeMapperOrdering.ts, 12, 44))
>I : Symbol(I, Decl(stableTypeMapperOrdering.ts, 11, 21))
>Same : Symbol(Same, Decl(stableTypeMapperOrdering.ts, 7, 1))
>I : Symbol(I, Decl(stableTypeMapperOrdering.ts, 11, 21))
>S : Symbol(S, Decl(stableTypeMapperOrdering.ts, 12, 53))

: never;

interface Group<Endpoints> {
>Group : Symbol(Group, Decl(stableTypeMapperOrdering.ts, 14, 12))
>Endpoints : Symbol(Endpoints, Decl(stableTypeMapperOrdering.ts, 16, 16))

add<N extends string, P = never>(
>add : Symbol(Group.add, Decl(stableTypeMapperOrdering.ts, 16, 28))
>N : Symbol(N, Decl(stableTypeMapperOrdering.ts, 17, 6))
>P : Symbol(P, Decl(stableTypeMapperOrdering.ts, 17, 23))

name: N,
>name : Symbol(name, Decl(stableTypeMapperOrdering.ts, 17, 35))
>N : Symbol(N, Decl(stableTypeMapperOrdering.ts, 17, 6))

params?: P,
>params : Symbol(params, Decl(stableTypeMapperOrdering.ts, 18, 12))
>P : Symbol(P, Decl(stableTypeMapperOrdering.ts, 17, 23))

): Group<Endpoints | Endpoint<N, P, never, never>>;
>Group : Symbol(Group, Decl(stableTypeMapperOrdering.ts, 14, 12))
>Endpoints : Symbol(Endpoints, Decl(stableTypeMapperOrdering.ts, 16, 16))
>Endpoint : Symbol(Endpoint, Decl(stableTypeMapperOrdering.ts, 0, 0))
>N : Symbol(N, Decl(stableTypeMapperOrdering.ts, 17, 6))
>P : Symbol(P, Decl(stableTypeMapperOrdering.ts, 17, 23))

middleware<I>(id: I): Group<AddMiddleware<Endpoints, I>>;
>middleware : Symbol(Group.middleware, Decl(stableTypeMapperOrdering.ts, 20, 53))
>I : Symbol(I, Decl(stableTypeMapperOrdering.ts, 21, 13))
>id : Symbol(id, Decl(stableTypeMapperOrdering.ts, 21, 16))
>I : Symbol(I, Decl(stableTypeMapperOrdering.ts, 21, 13))
>Group : Symbol(Group, Decl(stableTypeMapperOrdering.ts, 14, 12))
>AddMiddleware : Symbol(AddMiddleware, Decl(stableTypeMapperOrdering.ts, 9, 20))
>Endpoints : Symbol(Endpoints, Decl(stableTypeMapperOrdering.ts, 16, 16))
>I : Symbol(I, Decl(stableTypeMapperOrdering.ts, 21, 13))
}

declare const group: Group<never>;
>group : Symbol(group, Decl(stableTypeMapperOrdering.ts, 24, 13))
>Group : Symbol(Group, Decl(stableTypeMapperOrdering.ts, 14, 12))

export const result = group.add("a", { id: "" }).add("c").middleware("m" as const);
>result : Symbol(result, Decl(stableTypeMapperOrdering.ts, 26, 12))
>group.add("a", { id: "" }).add("c").middleware : Symbol(Group.middleware, Decl(stableTypeMapperOrdering.ts, 20, 53))
>group.add("a", { id: "" }).add : Symbol(Group.add, Decl(stableTypeMapperOrdering.ts, 16, 28))
>group.add : Symbol(Group.add, Decl(stableTypeMapperOrdering.ts, 16, 28))
>group : Symbol(group, Decl(stableTypeMapperOrdering.ts, 24, 13))
>add : Symbol(Group.add, Decl(stableTypeMapperOrdering.ts, 16, 28))
>id : Symbol(id, Decl(stableTypeMapperOrdering.ts, 26, 38))
>add : Symbol(Group.add, Decl(stableTypeMapperOrdering.ts, 16, 28))
>middleware : Symbol(Group.middleware, Decl(stableTypeMapperOrdering.ts, 20, 53))
>const : Symbol(const)

68 changes: 68 additions & 0 deletions tsc/testdata/baselines/reference/compiler/stableTypeMapperOrdering.types
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//// [tests/cases/compiler/stableTypeMapperOrdering.ts] ////

=== stableTypeMapperOrdering.ts ===
// https://github.com/microsoft/TypeScript/issues/64589

interface Endpoint<Name, Params, Middleware, Services> {
readonly name: Name;
>name : Name

readonly params: Params;
>params : Params

readonly middleware: Middleware;
>middleware : Middleware

readonly services: Services;
>services : Services
}

type Same<A, R> = R;
>Same : R

type AddMiddleware<E, I> =
>AddMiddleware : AddMiddleware<E, I>

E extends Endpoint<infer N, infer P, infer M, infer S>
? Endpoint<N, P, M | I, Same<I, S>>
: never;

interface Group<Endpoints> {
add<N extends string, P = never>(
>add : <N extends string, P = never>(name: N, params?: P) => Group<Endpoints | Endpoint<N, P, never, never>>

name: N,
>name : N

params?: P,
>params : P | undefined

): Group<Endpoints | Endpoint<N, P, never, never>>;
middleware<I>(id: I): Group<AddMiddleware<Endpoints, I>>;
>middleware : <I>(id: I) => Group<AddMiddleware<Endpoints, I>>
>id : I
}

declare const group: Group<never>;
>group : Group<never>

export const result = group.add("a", { id: "" }).add("c").middleware("m" as const);
>result : Group<Endpoint<"a", { id: string; }, "m", never> | Endpoint<"c", never, "m", never>>
>group.add("a", { id: "" }).add("c").middleware("m" as const) : Group<Endpoint<"a", { id: string; }, "m", never> | Endpoint<"c", never, "m", never>>
>group.add("a", { id: "" }).add("c").middleware : <I>(id: I) => Group<Endpoint<"a", { id: string; }, I, never> | Endpoint<"c", never, I, never>>
>group.add("a", { id: "" }).add("c") : Group<Endpoint<"a", { id: string; }, never, never> | Endpoint<"c", never, never, never>>
>group.add("a", { id: "" }).add : <N extends string, P = never>(name: N, params?: P | undefined) => Group<Endpoint<"a", { id: string; }, never, never> | Endpoint<N, P, never, never>>
>group.add("a", { id: "" }) : Group<Endpoint<"a", { id: string; }, never, never>>
>group.add : <N extends string, P = never>(name: N, params?: P | undefined) => Group<Endpoint<N, P, never, never>>
>group : Group<never>
>add : <N extends string, P = never>(name: N, params?: P | undefined) => Group<Endpoint<N, P, never, never>>
>"a" : "a"
>{ id: "" } : { id: string; }
>id : string
>"" : ""
>add : <N extends string, P = never>(name: N, params?: P | undefined) => Group<Endpoint<"a", { id: string; }, never, never> | Endpoint<N, P, never, never>>
>"c" : "c"
>middleware : <I>(id: I) => Group<Endpoint<"a", { id: string; }, I, never> | Endpoint<"c", never, I, never>>
>"m" as const : "m"
>"m" : "m"

29 changes: 29 additions & 0 deletions tsc/testdata/tests/cases/compiler/stableTypeMapperOrdering.ts
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// @declaration: true

// https://github.com/microsoft/TypeScript/issues/64589

interface Endpoint<Name, Params, Middleware, Services> {
readonly name: Name;
readonly params: Params;
readonly middleware: Middleware;
readonly services: Services;
}

type Same<A, R> = R;

type AddMiddleware<E, I> =
E extends Endpoint<infer N, infer P, infer M, infer S>
? Endpoint<N, P, M | I, Same<I, S>>
: never;

interface Group<Endpoints> {
add<N extends string, P = never>(
name: N,
params?: P,
): Group<Endpoints | Endpoint<N, P, never, never>>;
middleware<I>(id: I): Group<AddMiddleware<Endpoints, I>>;
}

declare const group: Group<never>;

export const result = group.add("a", { id: "" }).add("c").middleware("m" as const);
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