# implements-on-classes
* [Options](#user-content-implements-on-classes-options)
* [`contexts`](#user-content-implements-on-classes-options-contexts)
* [Context and settings](#user-content-implements-on-classes-context-and-settings)
* [Failing examples](#user-content-implements-on-classes-failing-examples)
* [Passing examples](#user-content-implements-on-classes-passing-examples)
Reports an issue with any non-constructor function using `@implements`.
Constructor functions, whether marked with `@class`, `@constructs`, or being
an ES6 class constructor, will not be flagged.
To indicate that a function follows another function's signature, one might
instead use `@type` to indicate the `@function` or `@callback` to which the
function is adhering.
## Options
A single options object has the following properties.
### contexts
Set this to an array of strings representing the AST context (or an object with
`context` and `comment` properties) where you wish the rule to be applied.
`context` defaults to `any` and `comment` defaults to no specific comment context.
Overrides the default contexts (`ArrowFunctionExpression`, `FunctionDeclaration`,
`FunctionExpression`). Set to `"any"` if you want
the rule to apply to any JSDoc block throughout your files (as is necessary
for finding function blocks not attached to a function declaration or
expression, i.e., `@callback` or `@function` (or its aliases `@func` or
`@method`) (including those associated with an `@interface`).
See the ["AST and Selectors"](#user-content-eslint-plugin-jsdoc-advanced-ast-and-selectors)
section of our Advanced docs for more on the expected format.
## Context and settings
|||
|---|---|
|Context|`ArrowFunctionExpression`, `FunctionDeclaration`, `FunctionExpression`; others when `contexts` option enabled|
|Tags|`implements` (prevented)|
|Recommended|true|
|Options|`contexts`|
## Failing examples
The following patterns are considered problems:
````ts
/**
* @implements {SomeClass}
*/
function quux () {
}
// Message: @implements used on a non-constructor function
/**
* @implements {SomeClass}
*/
function quux () {
}
// "jsdoc/implements-on-classes": ["error"|"warn", {"contexts":["any"]}]
// Message: @implements used on a non-constructor function
/**
* @function
* @implements {SomeClass}
*/
function quux () {
}
// "jsdoc/implements-on-classes": ["error"|"warn", {"contexts":["any"]}]
// Message: @implements used on a non-constructor function
/**
* @callback
* @implements {SomeClass}
*/
// "jsdoc/implements-on-classes": ["error"|"warn", {"contexts":["any"]}]
// Message: @implements used on a non-constructor function
/**
* @implements {SomeClass}
*/
function quux () {
}
// Settings: {"jsdoc":{"tagNamePreference":{"implements":false}}}
// Message: Unexpected tag `@implements`
class Foo {
/**
* @implements {SomeClass}
*/
constructor() {}
/**
* @implements {SomeClass}
*/
bar() {}
}
// "jsdoc/implements-on-classes": ["error"|"warn", {"contexts":["MethodDefinition"]}]
// Message: @implements used on a non-constructor function
class Foo {
/**
* @implements {SomeClass}
*/
constructor() {}
/**
* @implements {SomeClass}
*/
bar() {}
}
// "jsdoc/implements-on-classes": ["error"|"warn", {"contexts":["any"]}]
// Message: @implements used on a non-constructor function
````
## Passing examples
The following patterns are not considered problems:
````ts
/**
* @implements {SomeClass}
* @class
*/
function quux () {
}
/**
* @implements {SomeClass}
* @class
*/
function quux () {
}
// "jsdoc/implements-on-classes": ["error"|"warn", {"contexts":["any"]}]
/**
* @implements {SomeClass}
*/
// "jsdoc/implements-on-classes": ["error"|"warn", {"contexts":["any"]}]
/**
* @implements {SomeClass}
* @constructor
*/
function quux () {
}
/**
*
*/
class quux {
/**
* @implements {SomeClass}
*/
constructor () {
}
}
/**
*
*/
const quux = class {
/**
* @implements {SomeClass}
*/
constructor () {
}
}
/**
*
*/
function quux () {
}
/**
*
*/
function quux () {
}
// Settings: {"jsdoc":{"tagNamePreference":{"implements":false}}}
/**
* @function
* @implements {SomeClass}
*/
/**
* @callback
* @implements {SomeClass}
*/
````