no-redeclare
Disallow variable redeclaration.
Examples
This rule extends the base eslint/no-redeclare
rule.
It adds support for TypeScript function overloads, and declaration merging.
How to Use
module.exports = {
"rules": {
// Note: you must disable the base rule as it can report incorrect errors
"no-redeclare": "off",
"@typescript-eslint/no-redeclare": "warn"
}
};
Options
See eslint/no-redeclare
options.
This rule adds the following options:
interface Options extends BaseNoRedeclareOptions {
ignoreDeclarationMerge?: boolean;
}
const defaultOptions: Options = {
...baseNoRedeclareDefaultOptions,
ignoreDeclarationMerge: true,
};
ignoreDeclarationMerge
When set to true
, the rule will ignore declaration merges between the following sets:
- interface + interface
- namespace + namespace
- class + interface
- class + namespace
- class + interface + namespace
- function + namespace
- enum + namespace
Examples of correct code with { ignoreDeclarationMerge: true }
:
interface A {
prop1: 1;
}
interface A {
prop2: 2;
}
namespace Foo {
export const a = 1;
}
namespace Foo {
export const b = 2;
}
class Bar {}
namespace Bar {}
function Baz() {}
namespace Baz {}
Note: Even with this option set to true, this rule will report if you name a type and a variable the same name. This is intentional. Declaring a variable and a type and a variable the same is usually an accident, and it can lead to hard-to-understand code. If you have a rare case where you're intentionally naming a type the same name as a variable, use a disable comment. For example:
type something = string;
// eslint-disable-next-line @typescript-eslint/no-redeclare -- intentionally naming the variable the same as the type
const something = 2;
Taken with ❤️ from ESLint core