EC
TS2518
TypeScriptERRORNotableTypeHIGH confidence

A 'this'-based type guard is not compatible with a parameter-based type guard.

Production Risk

Build will fail; resolve before shipping.

What this means

A type-checking error (TS2518): A 'this'-based type guard is not compatible with a parameter-based type guard.. This diagnostic is emitted by the TypeScript compiler when a 'this'-based type guard is not compatible with a parameter-based type guard..

Why it happens
  1. 1The value type does not match the declared or expected type
  2. 2A type narrowing or assertion is needed
How to reproduce

TypeScript compiler reports TS2518 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS2518
// A 'this'-based type guard is not compatible with a parameter-based type guard.

expected output

error TS2518: A 'this'-based type guard is not compatible with a parameter-based type guard.

Fix

Address the TypeScript diagnostic

WHEN When this error is reported by the compiler

Address the TypeScript diagnostic
// Run the TypeScript compiler for details:
npx tsc --noEmit
// Use the TypeScript playground to test your code:
// https://www.typescriptlang.org/play

Why this works

Review the full error message and location; the TypeScript handbook provides guidance on each error category.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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