<
R,
Ret,
P extends {
readonly [Tag in Types.Tags<"_tag", R> & string]?:
| ((_: Extract<R, Record<"_tag", Tag>>) => Ret)
| undefined
} & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never }
>(
fields: P
): <I, F, A, Pr>(
self: Matcher<I, F, R, A, Pr, Ret>
) => Matcher<
I,
Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>,
Types.ApplyFilters<
I,
Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>
>,
A | ReturnType<P[keyof P] & {}>,
Pr,
Ret
>Matches values based on their _tag field, mapping each tag to a
corresponding handler.
Details
This function provides a way to handle discriminated unions by mapping _tag
values to specific functions. Each handler receives the matched value and
returns a transformed result. If all possible tags are handled, you can
enforce exhaustiveness using Match.exhaustive to ensure no case is missed.
Example (Mapping tag handlers)
import { Match, pipe } from "effect"
const match = pipe(
Match.type<
{ _tag: "A"; a: string } | { _tag: "B"; b: number } | {
_tag: "C"
c: boolean
}
>(),
Match.tags({
A: (a) => a.a,
B: (b) => b.b,
C: (c) => c.c
}),
Match.exhaustive
)Defining patterns
Source effect/Match.ts:104118 lines
export const const tags: <
R,
Ret,
P extends {
readonly [Tag in Types.Tags<"_tag", R> &
string]?:
| ((
_: Extract<R, Record<"_tag", Tag>>
) => Ret)
| undefined
} & {
readonly [Tag in Exclude<
keyof P,
Types.Tags<"_tag", R>
>]: never
}
>(
fields: P
) => <I, F, A, Pr>(
self: Matcher<I, F, R, A, Pr, Ret>
) => Matcher<
I,
Types.AddWithout<
F,
Extract<R, Record<"_tag", keyof P>>
>,
Types.ApplyFilters<
I,
Types.AddWithout<
F,
Extract<R, Record<"_tag", keyof P>>
>
>,
A | ReturnType<P[keyof P] & {}>,
Pr,
Ret
>
Matches values based on their _tag field, mapping each tag to a
corresponding handler.
Details
This function provides a way to handle discriminated unions by mapping _tag
values to specific functions. Each handler receives the matched value and
returns a transformed result. If all possible tags are handled, you can
enforce exhaustiveness using Match.exhaustive to ensure no case is missed.
Example (Mapping tag handlers)
import { Match, pipe } from "effect"
const match = pipe(
Match.type<
{ _tag: "A"; a: string } | { _tag: "B"; b: number } | {
_tag: "C"
c: boolean
}
>(),
Match.tags({
A: (a) => a.a,
B: (b) => b.b,
C: (c) => c.c
}),
Match.exhaustive
)
tags: <
function (type parameter) R in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>R,
function (type parameter) Ret in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>Ret,
function (type parameter) P in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>P extends
& { readonly [function (type parameter) TagTag in Types.type Types.Tags<D extends string, P> = P extends Record<D, infer X> ? X : neverExtracts tag values from a discriminated union based on a discriminant field.
Details
This utility type extracts the possible values of a discriminant field
from a union type. It's used internally to implement tag-based pattern
matching for discriminated unions.
Example (Extracting discriminator tags)
import type { Match } from "effect"
type Events =
| { _tag: "click"; x: number; y: number }
| { _tag: "keypress"; key: string }
| { _tag: "scroll"; delta: number }
type EventTags = Match.Types.Tags<"_tag", Events>
// Result: "click" | "keypress" | "scroll"
type CustomTags = Match.Types.Tags<
"type",
| { type: "user"; name: string }
| { type: "admin"; permissions: Array<string> }
>
// Result: "user" | "admin"
Tags<"_tag", function (type parameter) R in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>_: type Extract<T, U> = T extends U
? T
: never
Extract from T those types that are assignable to U
Extract<function (type parameter) R in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>R, type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<"_tag", function (type parameter) TagTag>>) => function (type parameter) Ret in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>Ret) | undefined }
& { readonly [function (type parameter) TagTag in type Exclude<T, U> = T extends U
? never
: T
Exclude from T those types that are assignable to U
Exclude<keyof function (type parameter) P in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>P, Types.type Types.Tags<D extends string, P> = P extends Record<D, infer X> ? X : neverExtracts tag values from a discriminated union based on a discriminant field.
Details
This utility type extracts the possible values of a discriminant field
from a union type. It's used internally to implement tag-based pattern
matching for discriminated unions.
Example (Extracting discriminator tags)
import type { Match } from "effect"
type Events =
| { _tag: "click"; x: number; y: number }
| { _tag: "keypress"; key: string }
| { _tag: "scroll"; delta: number }
type EventTags = Match.Types.Tags<"_tag", Events>
// Result: "click" | "keypress" | "scroll"
type CustomTags = Match.Types.Tags<
"type",
| { type: "user"; name: string }
| { type: "admin"; permissions: Array<string> }
>
// Result: "user" | "admin"
Tags<"_tag", function (type parameter) R in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>R>>]: never }
>(
fields: P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }fields: function (type parameter) P in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>P
) => <function (type parameter) I in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>I, function (type parameter) F in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>F, function (type parameter) A in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>A, function (type parameter) Pr in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>Pr>(
self: Matcher<I, F, R, A, Pr, Ret>self: type Matcher<
Input,
Filters,
RemainingApplied,
Result,
Provided,
Return = any
> =
| TypeMatcher<
Input,
Filters,
RemainingApplied,
Result,
Return
>
| ValueMatcher<
Input,
Filters,
RemainingApplied,
Result,
Provided,
Return
>
Union type for matchers created by Match.type and Match.value.
Details
A Matcher carries the input type, accumulated filters, remaining cases,
result type, and, for value matchers, the provided value being matched.
Example (Matching string and number values)
import { Match } from "effect"
// Simulated dynamic input that can be a string or a number
const input: string | number = "some input"
// ┌─── string
// ▼
const result = Match.value(input).pipe(
// Match if the value is a number
Match.when(Match.number, (n) => `number: ${n}`),
// Match if the value is a string
Match.when(Match.string, (s) => `string: ${s}`),
// Ensure all possible cases are covered
Match.exhaustive
)
console.log(result)
// Output: "string: some input"
Matcher<function (type parameter) I in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>I, function (type parameter) F in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>F, function (type parameter) R in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>R, function (type parameter) A in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>A, function (type parameter) Pr in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>Pr, function (type parameter) Ret in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>Ret>
) => type Matcher<
Input,
Filters,
RemainingApplied,
Result,
Provided,
Return = any
> =
| TypeMatcher<
Input,
Filters,
RemainingApplied,
Result,
Return
>
| ValueMatcher<
Input,
Filters,
RemainingApplied,
Result,
Provided,
Return
>
Union type for matchers created by Match.type and Match.value.
Details
A Matcher carries the input type, accumulated filters, remaining cases,
result type, and, for value matchers, the provided value being matched.
Example (Matching string and number values)
import { Match } from "effect"
// Simulated dynamic input that can be a string or a number
const input: string | number = "some input"
// ┌─── string
// ▼
const result = Match.value(input).pipe(
// Match if the value is a number
Match.when(Match.number, (n) => `number: ${n}`),
// Match if the value is a string
Match.when(Match.string, (s) => `string: ${s}`),
// Ensure all possible cases are covered
Match.exhaustive
)
console.log(result)
// Output: "string: some input"
Matcher<
function (type parameter) I in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>I,
Types.type Types.AddWithout<A, X> = [A] extends [Types.Without<infer WX>] ? Types.Without<X | WX> : [A] extends [Types.Only<infer OX>] ? Types.Only<Exclude<OX, X>> : neverAdds a type to the exclusion filter, expanding what should be filtered out.
Details
This utility type manages the accumulation of excluded types during
pattern matching. When multiple exclusions are applied, it combines
them into a single filter representation.
Example (Accumulating excluded types)
import { Match } from "effect"
// AddWithout is used when combining multiple exclusions:
Match.type<string | number | boolean | null>().pipe(
Match.not(Match.string, () => "not string"),
Match.not(Match.number, () => "not number"),
// Type system uses AddWithout to combine exclusions
Match.orElse(() => "was string or number")
)
AddWithout<function (type parameter) F in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>F, type Extract<T, U> = T extends U
? T
: never
Extract from T those types that are assignable to U
Extract<function (type parameter) R in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>R, type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<"_tag", keyof function (type parameter) P in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>P>>>,
Types.type Types.ApplyFilters<I, A> = A extends Types.Only<infer X> ? X : A extends Types.Without<infer X> ? Exclude<I, X> : neverApplies accumulated filters to an input type, producing the final narrowed type.
Details
This utility type takes the collected inclusion/exclusion filters and
applies them to the input type to compute the final narrowed result.
It's the culmination of the type-level filtering process.
Example (Applying accumulated filters)
import type { Match } from "effect"
// ApplyFilters computes the final narrowed type:
type Result = Match.Types.ApplyFilters<
string | number | boolean,
Match.Types.Only<string>
>
// Result: string
type ExclusionResult = Match.Types.ApplyFilters<
string | number | boolean,
Match.Types.Without<string>
>
// Result: number | boolean
ApplyFilters<function (type parameter) I in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>I, Types.type Types.AddWithout<A, X> = [A] extends [Types.Without<infer WX>] ? Types.Without<X | WX> : [A] extends [Types.Only<infer OX>] ? Types.Only<Exclude<OX, X>> : neverAdds a type to the exclusion filter, expanding what should be filtered out.
Details
This utility type manages the accumulation of excluded types during
pattern matching. When multiple exclusions are applied, it combines
them into a single filter representation.
Example (Accumulating excluded types)
import { Match } from "effect"
// AddWithout is used when combining multiple exclusions:
Match.type<string | number | boolean | null>().pipe(
Match.not(Match.string, () => "not string"),
Match.not(Match.number, () => "not number"),
// Type system uses AddWithout to combine exclusions
Match.orElse(() => "was string or number")
)
AddWithout<function (type parameter) F in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>F, type Extract<T, U> = T extends U
? T
: never
Extract from T those types that are assignable to U
Extract<function (type parameter) R in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>R, type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<"_tag", keyof function (type parameter) P in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>P>>>>,
function (type parameter) A in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>A | type ReturnType<
T extends (...args: any) => any
> = T extends (...args: any) => infer R ? R : any
Obtain the return type of a function type
ReturnType<function (type parameter) P in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>P[keyof function (type parameter) P in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>P] & {}>,
function (type parameter) Pr in <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>): Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>Pr,
function (type parameter) Ret in <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P): <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>Ret
> = import internalinternal.const tags: <R, Ret, P extends { readonly [Tag in Types.Tags<"_tag", R> & string]?: ((_: Extract<R, Record<"_tag", Tag>>) => Ret) | undefined; } & { readonly [Tag in Exclude<keyof P, Types.Tags<"_tag", R>>]: never; }>(fields: P) => <I, F, A, Pr>(self: Matcher<...>) => Matcher<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>, Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<"_tag", keyof P>>>>, A | ReturnType<P[keyof P] & {}>, Pr, Ret>tagsReferenced by 1 symbols