EC
TS2720
TypeScriptERRORNotableTypeHIGH confidence

Class 'X' incorrectly implements class 'X'. Did you mean to extend 'X' and in...

Production Risk

Build will fail; resolve before shipping.

What this means

A type-checking error (TS2720): Class 'X' incorrectly implements class 'X'. Did you mean to extend 'X' and inherit its members as a subclass?. This diagnostic is emitted by the TypeScript compiler when class 'X' incorrectly implements class 'X'. Did you mean to extend 'X' and inherit its members as a subclass?.

Why it happens
  1. 1Incorrect TypeScript syntax or type usage
  2. 2Type mismatch between declared and actual value
How to reproduce

TypeScript compiler reports TS2720 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS2720
// Class 'X' incorrectly implements class 'X'. Did you mean to extend 'X' and inherit its members as a subclass?

expected output

error TS2720: Class 'X' incorrectly implements class 'X'. Did you mean to extend 'X' and inherit its members as a subclass?

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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