EC
TS1245
TypeScriptERRORNotableSyntaxHIGH confidence

Method 'X' cannot have an implementation because it is marked abstract.

Production Risk

Build will fail; resolve before shipping.

What this means

A syntax error (TS1245): Method 'X' cannot have an implementation because it is marked abstract.. This diagnostic is emitted by the TypeScript compiler when method 'X' cannot have an implementation because it is marked abstract..

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

TypeScript compiler reports TS1245 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS1245
// Method 'X' cannot have an implementation because it is marked abstract.

expected output

error TS1245: Method 'X' cannot have an implementation because it is marked abstract.

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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