effect-io-ai

Package: effect
Module: Match

Match.instanceOfUnsafe

Checks whether a value is an instance of a constructor without type-safe narrowing.

When to use

Use when you need constructor matching to use the unsafe refinement type.

Details

This predicate checks if a value is an instance of the specified constructor but doesn’t provide the same type safety guarantees as the regular instanceOf. Use this when you need more flexibility but understand the type safety implications.

Example (Matching class instances unsafely)

import { Match } from "effect"

class CustomError extends Error {
  constructor(message: string, public code: number) {
    super(message)
  }
}

// When you need to match instances but handle type narrowing manually
const handleError = Match.type<unknown>().pipe(
  Match.when(Match.instanceOfUnsafe(CustomError), (err: any) => {
    // Manual type assertion needed
    const customErr = err as CustomError
    return `Custom error ${customErr.code}: ${customErr.message}`
  }),
  Match.orElse(() => "Not a CustomError")
)

See

• instanceOf for type-safe constructor matching

Signature

declare const instanceOfUnsafe: <A extends abstract new (...args: any) => any>(constructor: A) => SafeRefinement<InstanceType<A>, InstanceType<A>>

Source

Since v4.0.0