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Unwrap NoInfer-wrapped unions before conditional type distribution attempt #61077

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Unwrap NoInfer-wrapped unions before conditional type distribution attempt #61077

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e9939f6
Unwrap `NoInfer`-wrapped unions before conditional type distribution …
Andarist Jan 29, 2025
892d183
unwrap them in `canTailRecurse` too
Andarist Jan 30, 2025
5a0d2de
Merge remote-tracking branch 'origin/main' into fix/unwrap-noinfer-be…
Andarist Nov 4, 2025
390aad2
add extra test case
Andarist Nov 4, 2025
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10 changes: 8 additions & 2 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -19832,7 +19832,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
const typeParamMapper = combineTypeMappers((newType as ConditionalType).mapper, newMapper);
const typeArguments = map(newRoot.outerTypeParameters, t => getMappedType(t, typeParamMapper));
const newRootMapper = createTypeMapper(newRoot.outerTypeParameters, typeArguments);
const newCheckType = newRoot.isDistributive ? getMappedType(newRoot.checkType, newRootMapper) : undefined;
let newCheckType = newRoot.isDistributive ? getMappedType(newRoot.checkType, newRootMapper) : undefined;
if (newCheckType && isNoInferType(newCheckType)) {
newCheckType = (newCheckType as SubstitutionType).baseType;
}
if (!newCheckType || newCheckType === newRoot.checkType || !(newCheckType.flags & (TypeFlags.Union | TypeFlags.Never))) {
root = newRoot;
mapper = newRootMapper;
Expand Down Expand Up @@ -20928,7 +20931,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
if (!result) {
const newMapper = createTypeMapper(root.outerTypeParameters, typeArguments);
const checkType = root.checkType;
const distributionType = root.isDistributive ? getReducedType(getMappedType(checkType, newMapper)) : undefined;
let distributionType = root.isDistributive ? getReducedType(getMappedType(checkType, newMapper)) : undefined;
if (distributionType && isNoInferType(distributionType)) {
distributionType = (distributionType as SubstitutionType).baseType;
}
// Distributive conditional types are distributed over union types. For example, when the
// distributive conditional type T extends U ? X : Y is instantiated with A | B for T, the
// result is (A extends U ? X : Y) | (B extends U ? X : Y).
Expand Down
128 changes: 128 additions & 0 deletions tests/baselines/reference/noInferVsDistributiveConditionalType1.symbols
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@@ -0,0 +1,128 @@
//// [tests/cases/conformance/types/typeRelationships/typeInference/noInferVsDistributiveConditionalType1.ts] ////

=== noInferVsDistributiveConditionalType1.ts ===
// https://github.com/microsoft/TypeScript/issues/61076

type FooEvent = { type: "FOO" };
>FooEvent : Symbol(FooEvent, Decl(noInferVsDistributiveConditionalType1.ts, 0, 0))
>type : Symbol(type, Decl(noInferVsDistributiveConditionalType1.ts, 2, 17))

type BarEvent = { type: "BAR" };
>BarEvent : Symbol(BarEvent, Decl(noInferVsDistributiveConditionalType1.ts, 2, 32))
>type : Symbol(type, Decl(noInferVsDistributiveConditionalType1.ts, 3, 17))

type Input = FooEvent | BarEvent;
>Input : Symbol(Input, Decl(noInferVsDistributiveConditionalType1.ts, 3, 32))
>FooEvent : Symbol(FooEvent, Decl(noInferVsDistributiveConditionalType1.ts, 0, 0))
>BarEvent : Symbol(BarEvent, Decl(noInferVsDistributiveConditionalType1.ts, 2, 32))

type Result = Extract<NoInfer<Input>, FooEvent>;
>Result : Symbol(Result, Decl(noInferVsDistributiveConditionalType1.ts, 5, 33))
>Extract : Symbol(Extract, Decl(lib.es5.d.ts, --, --))
>NoInfer : Symbol(NoInfer, Decl(lib.es5.d.ts, --, --))
>Input : Symbol(Input, Decl(noInferVsDistributiveConditionalType1.ts, 3, 32))
>FooEvent : Symbol(FooEvent, Decl(noInferVsDistributiveConditionalType1.ts, 0, 0))

type EventObject = {
>EventObject : Symbol(EventObject, Decl(noInferVsDistributiveConditionalType1.ts, 6, 48))

type: string;
>type : Symbol(type, Decl(noInferVsDistributiveConditionalType1.ts, 8, 20))

};

type ActionFunction<
>ActionFunction : Symbol(ActionFunction, Decl(noInferVsDistributiveConditionalType1.ts, 10, 2))

TExpressionEvent extends EventObject,
>TExpressionEvent : Symbol(TExpressionEvent, Decl(noInferVsDistributiveConditionalType1.ts, 12, 20))
>EventObject : Symbol(EventObject, Decl(noInferVsDistributiveConditionalType1.ts, 6, 48))

TEvent extends EventObject,
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 13, 39))
>EventObject : Symbol(EventObject, Decl(noInferVsDistributiveConditionalType1.ts, 6, 48))

> = {
(args: { event: TExpressionEvent }): void;
>args : Symbol(args, Decl(noInferVsDistributiveConditionalType1.ts, 16, 3))
>event : Symbol(event, Decl(noInferVsDistributiveConditionalType1.ts, 16, 10))
>TExpressionEvent : Symbol(TExpressionEvent, Decl(noInferVsDistributiveConditionalType1.ts, 12, 20))

_out_TEvent?: TEvent;
>_out_TEvent : Symbol(_out_TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 16, 44))
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 13, 39))

};

type TransitionsConfig<TEvent extends EventObject> = {
>TransitionsConfig : Symbol(TransitionsConfig, Decl(noInferVsDistributiveConditionalType1.ts, 18, 2))
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 20, 23))
>EventObject : Symbol(EventObject, Decl(noInferVsDistributiveConditionalType1.ts, 6, 48))

[K in TEvent["type"]]?: {
>K : Symbol(K, Decl(noInferVsDistributiveConditionalType1.ts, 21, 3))
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 20, 23))

actions?: ActionFunction<Extract<TEvent, { type: K }>, TEvent>;
>actions : Symbol(actions, Decl(noInferVsDistributiveConditionalType1.ts, 21, 27))
>ActionFunction : Symbol(ActionFunction, Decl(noInferVsDistributiveConditionalType1.ts, 10, 2))
>Extract : Symbol(Extract, Decl(lib.es5.d.ts, --, --))
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 20, 23))
>type : Symbol(type, Decl(noInferVsDistributiveConditionalType1.ts, 22, 46))
>K : Symbol(K, Decl(noInferVsDistributiveConditionalType1.ts, 21, 3))
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 20, 23))

};
};

declare function createMachine<TEvent extends EventObject>(config: {
>createMachine : Symbol(createMachine, Decl(noInferVsDistributiveConditionalType1.ts, 24, 2))
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 26, 31))
>EventObject : Symbol(EventObject, Decl(noInferVsDistributiveConditionalType1.ts, 6, 48))
>config : Symbol(config, Decl(noInferVsDistributiveConditionalType1.ts, 26, 59))

types?: {
>types : Symbol(types, Decl(noInferVsDistributiveConditionalType1.ts, 26, 68))

events?: TEvent;
>events : Symbol(events, Decl(noInferVsDistributiveConditionalType1.ts, 27, 11))
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 26, 31))

};
on?: TransitionsConfig<NoInfer<TEvent>>;
>on : Symbol(on, Decl(noInferVsDistributiveConditionalType1.ts, 29, 4))
>TransitionsConfig : Symbol(TransitionsConfig, Decl(noInferVsDistributiveConditionalType1.ts, 18, 2))
>NoInfer : Symbol(NoInfer, Decl(lib.es5.d.ts, --, --))
>TEvent : Symbol(TEvent, Decl(noInferVsDistributiveConditionalType1.ts, 26, 31))

}): void;

createMachine({
>createMachine : Symbol(createMachine, Decl(noInferVsDistributiveConditionalType1.ts, 24, 2))

types: {
>types : Symbol(types, Decl(noInferVsDistributiveConditionalType1.ts, 33, 15))

events: {} as Input,
>events : Symbol(events, Decl(noInferVsDistributiveConditionalType1.ts, 34, 10))
>Input : Symbol(Input, Decl(noInferVsDistributiveConditionalType1.ts, 3, 32))

},
on: {
>on : Symbol(on, Decl(noInferVsDistributiveConditionalType1.ts, 36, 4))

FOO: {
>FOO : Symbol(FOO, Decl(noInferVsDistributiveConditionalType1.ts, 37, 7))

actions: ({ event }) => {
>actions : Symbol(actions, Decl(noInferVsDistributiveConditionalType1.ts, 38, 10))
>event : Symbol(event, Decl(noInferVsDistributiveConditionalType1.ts, 39, 17))

event; // { type: "FOO"; }
>event : Symbol(event, Decl(noInferVsDistributiveConditionalType1.ts, 39, 17))

},
},
},
});

141 changes: 141 additions & 0 deletions tests/baselines/reference/noInferVsDistributiveConditionalType1.types
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@@ -0,0 +1,141 @@
//// [tests/cases/conformance/types/typeRelationships/typeInference/noInferVsDistributiveConditionalType1.ts] ////

=== noInferVsDistributiveConditionalType1.ts ===
// https://github.com/microsoft/TypeScript/issues/61076

type FooEvent = { type: "FOO" };
>FooEvent : FooEvent
> : ^^^^^^^^
>type : "FOO"
> : ^^^^^

type BarEvent = { type: "BAR" };
>BarEvent : BarEvent
> : ^^^^^^^^
>type : "BAR"
> : ^^^^^

type Input = FooEvent | BarEvent;
>Input : Input
> : ^^^^^

type Result = Extract<NoInfer<Input>, FooEvent>;
>Result : FooEvent
> : ^^^^^^^^

type EventObject = {
>EventObject : EventObject
> : ^^^^^^^^^^^

type: string;
>type : string
> : ^^^^^^

};

type ActionFunction<
>ActionFunction : ActionFunction<TExpressionEvent, TEvent>
> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

TExpressionEvent extends EventObject,
TEvent extends EventObject,
> = {
(args: { event: TExpressionEvent }): void;
>args : { event: TExpressionEvent; }
> : ^^^^^^^^^ ^^^
>event : TExpressionEvent
> : ^^^^^^^^^^^^^^^^

_out_TEvent?: TEvent;
>_out_TEvent : TEvent | undefined
> : ^^^^^^^^^^^^^^^^^^

};

type TransitionsConfig<TEvent extends EventObject> = {
>TransitionsConfig : TransitionsConfig<TEvent>
> : ^^^^^^^^^^^^^^^^^^^^^^^^^

[K in TEvent["type"]]?: {
actions?: ActionFunction<Extract<TEvent, { type: K }>, TEvent>;
>actions : ActionFunction<Extract<TEvent, { type: K; }>, TEvent> | undefined
> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^
>type : K
> : ^

};
};

declare function createMachine<TEvent extends EventObject>(config: {
>createMachine : <TEvent extends EventObject>(config: { types?: { events?: TEvent; }; on?: TransitionsConfig<NoInfer<TEvent>>; }) => void
> : ^ ^^^^^^^^^ ^^ ^^ ^^^^^
>config : { types?: { events?: TEvent; }; on?: TransitionsConfig<NoInfer<TEvent>>; }
> : ^^^^^^^^^^ ^^^^^^^ ^^^

types?: {
>types : { events?: TEvent; } | undefined
> : ^^^^^^^^^^^ ^^^^^^^^^^^^^^^

events?: TEvent;
>events : TEvent | undefined
> : ^^^^^^^^^^^^^^^^^^

};
on?: TransitionsConfig<NoInfer<TEvent>>;
>on : TransitionsConfig<NoInfer<TEvent>> | undefined
> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

}): void;

createMachine({
>createMachine({ types: { events: {} as Input, }, on: { FOO: { actions: ({ event }) => { event; // { type: "FOO"; } }, }, },}) : void
> : ^^^^
>createMachine : <TEvent extends EventObject>(config: { types?: { events?: TEvent; }; on?: TransitionsConfig<NoInfer<TEvent>>; }) => void
> : ^ ^^^^^^^^^ ^^ ^^ ^^^^^
>{ types: { events: {} as Input, }, on: { FOO: { actions: ({ event }) => { event; // { type: "FOO"; } }, }, },} : { types: { events: Input; }; on: { FOO: { actions: ({ event }: { event: FooEvent; }) => void; }; }; }
> : ^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

types: {
>types : { events: Input; }
> : ^^^^^^^^^^ ^^^
>{ events: {} as Input, } : { events: Input; }
> : ^^^^^^^^^^ ^^^

events: {} as Input,
>events : Input
> : ^^^^^
>{} as Input : Input
> : ^^^^^
>{} : {}
> : ^^

},
on: {
>on : { FOO: { actions: ({ event }: { event: FooEvent; }) => void; }; }
> : ^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>{ FOO: { actions: ({ event }) => { event; // { type: "FOO"; } }, }, } : { FOO: { actions: ({ event }: { event: FooEvent; }) => void; }; }
> : ^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

FOO: {
>FOO : { actions: ({ event }: { event: FooEvent; }) => void; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>{ actions: ({ event }) => { event; // { type: "FOO"; } }, } : { actions: ({ event }: { event: FooEvent; }) => void; }
> : ^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

actions: ({ event }) => {
>actions : ({ event }: { event: FooEvent; }) => void
> : ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>({ event }) => { event; // { type: "FOO"; } } : ({ event }: { event: FooEvent; }) => void
> : ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>event : FooEvent
> : ^^^^^^^^

event; // { type: "FOO"; }
>event : FooEvent
> : ^^^^^^^^

},
},
},
});

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