EC
TS2656
TypeScriptERRORNotableTypeHIGH confidence

Non-abstract class expression is missing implementations for the following me...

Production Risk

Build will fail; resolve before shipping.

What this means

A type-checking error (TS2656): Non-abstract class expression is missing implementations for the following members of 'X': X.. This diagnostic is emitted by the TypeScript compiler when non-abstract class expression is missing implementations for the following members of 'X': X..

Why it happens
  1. 1The function overload signatures do not match the implementation
How to reproduce

TypeScript compiler reports TS2656 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS2656
// Non-abstract class expression is missing implementations for the following members of 'X': X.

expected output

error TS2656: Non-abstract class expression is missing implementations for the following members of 'X': X.

Fix

Implement all abstract members

WHEN Extending an abstract class

Implement all abstract members
abstract class Base {
  abstract doWork(): void;
}
class Derived extends Base {
  doWork(): void { /* implementation */ }
}

Why this works

All abstract members must be implemented in concrete subclasses.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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