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noEmptyInterface (since v1.0.0)

Diagnostic Category: lint/suspicious/noEmptyInterface


Disallow the declaration of empty interfaces.

An empty interface in TypeScript does very little: any non-nullable value is assignable to {}. Using an empty interface is often a sign of programmer error, such as misunderstanding the concept of {} or forgetting to fill in fields.

The rule ignores empty interfaces that extends one or multiple types.

interface A {}
suspicious/noEmptyInterface.js:1:1 lint/suspicious/noEmptyInterface  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━

   An empty interface is equivalent to {}.
  > 1 │ interface A {}
    2 │ 
   Safe fix: Use a type alias instead.
    1  - interface·A·{}
      1+ type·A·=·{}
    2 2  
interface A {
prop: string;
// Allow empty interfaces that extend a type.
interface B extends A {}