effect-io-ai

Package: effect
Module: Function

Function.satisfies

Ensures that the type of an expression matches some type, without changing the resulting type of that expression.

When to use

Use to check assignability while preserving the expression’s precise inferred type.

Example (Checking an expression against a type)

import { Function } from "effect"
import * as assert from "node:assert"

const test1 = Function.satisfies<number>()(5 as const)
// ^? const test: 5
// @ts-expect-error
const test2 = Function.satisfies<string>()(5)
// ^? Argument of type 'number' is not assignable to parameter of type 'string'

assert.deepStrictEqual(Function.satisfies<number>()(5), 5)

See

• cast for changing only the static TypeScript type

Signature

declare const satisfies: <A>() => <B extends A>(b: B) => B

Source

Since v2.0.0