<E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(
self: Effect<A, E, R>
) => Effect<A | B, E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect<A, E, R>,
f: (e: NoInfer<E>) => Effect<B, E2, R2>
): Effect<A | B, E2, R | R2>Applies catch eagerly when an effect is already resolved.
When to use
Use when an already-resolved failed effect should recover immediately while pending effects still use regular error recovery.
Details
Success effects pass through unchanged because there is no error to catch.
Failure effects apply the catch function immediately, and pending effects
fall back to regular catch behavior.
Example (Catching failures eagerly when possible)
import { Effect } from "effect"
// For resolved failure effects, the catch function is applied immediately
const failed = Effect.fail("original error")
const recovered = Effect.catchEager(
failed,
(err: string) => Effect.succeed(`recovered from: ${err}`)
) // Applied eagerly
// For success effects, returns success as-is
const success = Effect.succeed(42)
const unchanged = Effect.catchEager(
success,
(err: string) => Effect.succeed(`recovered from: ${err}`)
) // Returns success as-is
// For pending effects, behaves like regular catch
const pending = Effect.delay(Effect.fail("error"), "100 millis")
const recoveredPending = Effect.catchEager(
pending,
(err: string) => Effect.succeed(`recovered from: ${err}`)
) // Uses regular catchexport const const catchEager: {
<E, B, E2, R2>(
f: (e: NoInfer<E>) => Effect<B, E2, R2>
): <A, R>(
self: Effect<A, E, R>
) => Effect<A | B, E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect<A, E, R>,
f: (e: NoInfer<E>) => Effect<B, E2, R2>
): Effect<A | B, E2, R | R2>
}
Applies catch eagerly when an effect is already resolved.
When to use
Use when an already-resolved failed effect should recover immediately while
pending effects still use regular error recovery.
Details
Success effects pass through unchanged because there is no error to catch.
Failure effects apply the catch function immediately, and pending effects
fall back to regular catch behavior.
Example (Catching failures eagerly when possible)
import { Effect } from "effect"
// For resolved failure effects, the catch function is applied immediately
const failed = Effect.fail("original error")
const recovered = Effect.catchEager(
failed,
(err: string) => Effect.succeed(`recovered from: ${err}`)
) // Applied eagerly
// For success effects, returns success as-is
const success = Effect.succeed(42)
const unchanged = Effect.catchEager(
success,
(err: string) => Effect.succeed(`recovered from: ${err}`)
) // Returns success as-is
// For pending effects, behaves like regular catch
const pending = Effect.delay(Effect.fail("error"), "100 millis")
const recoveredPending = Effect.catchEager(
pending,
(err: string) => Effect.succeed(`recovered from: ${err}`)
) // Uses regular catch
catchEager: {
<function (type parameter) E in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>E, function (type parameter) B in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>B, function (type parameter) E2 in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>E2, function (type parameter) R2 in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>R2>(
f: (e: NoInfer<E>) => Effect<B, E2, R2>f: (e: NoInfer<E>e: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) E in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>E>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) B in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>B, function (type parameter) E2 in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>E2, function (type parameter) R2 in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>R2>
): <function (type parameter) A in <A, R>(self: Effect<A, E, R>): Effect<A | B, E2, R | R2>A, function (type parameter) R in <A, R>(self: Effect<A, E, R>): Effect<A | B, E2, R | R2>R>(self: Effect<A, E, R>(parameter) self: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, R>(self: Effect<A, E, R>): Effect<A | B, E2, R | R2>A, function (type parameter) E in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>E, function (type parameter) R in <A, R>(self: Effect<A, E, R>): Effect<A | B, E2, R | R2>R>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, R>(self: Effect<A, E, R>): Effect<A | B, E2, R | R2>A | function (type parameter) B in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>B, function (type parameter) E2 in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>E2, function (type parameter) R in <A, R>(self: Effect<A, E, R>): Effect<A | B, E2, R | R2>R | function (type parameter) R2 in <E, B, E2, R2>(f: (e: NoInfer<E>) => Effect<B, E2, R2>): <A, R>(self: Effect<A, E, R>) => Effect<A | B, E2, R | R2>R2>
<function (type parameter) A in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>A, function (type parameter) E in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>E, function (type parameter) R in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>R, function (type parameter) B in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>B, function (type parameter) E2 in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>E2, function (type parameter) R2 in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>R2>(
self: Effect<A, E, R>(parameter) self: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>A, function (type parameter) E in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>E, function (type parameter) R in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>R>,
f: (e: NoInfer<E>) => Effect<B, E2, R2>f: (e: NoInfer<E>e: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) E in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>E>) => interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) B in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>B, function (type parameter) E2 in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>E2, function (type parameter) R2 in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>R2>
): interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<function (type parameter) A in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>A | function (type parameter) B in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>B, function (type parameter) E2 in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>E2, function (type parameter) R in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>R | function (type parameter) R2 in <A, E, R, B, E2, R2>(self: Effect<A, E, R>, f: (e: NoInfer<E>) => Effect<B, E2, R2>): Effect<A | B, E2, R | R2>R2>
} = import internalinternal.const catchEager: {
<E, B, E2, R2>(
f: (e: NoInfer<E>) => Effect.Effect<B, E2, R2>
): <A, R>(
self: Effect.Effect<A, E, R>
) => Effect.Effect<A | B, E2, R | R2>
<A, E, R, B, E2, R2>(
self: Effect.Effect<A, E, R>,
f: (e: NoInfer<E>) => Effect.Effect<B, E2, R2>
): Effect.Effect<A | B, E2, R | R2>
}