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noRedeclare (since v1.0.0)

Diagnostic Category: lint/suspicious/noRedeclare

Sources:

Disallow variable, function, class, and type redeclarations in the same scope.

Examples

Section titled Examples

Invalid

Section titled Invalid
var a = 3;
var a = 10;
code-block.js:2:5 lint/suspicious/noRedeclare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Shouldn't redeclare 'a'. Consider to delete it or rename it.
  
    1 │ var a = 3;
  > 2 │ var a = 10;
      │     ^
    3 │ 
  
  ℹ 'a' is defined here:
  
  > 1 │ var a = 3;
      │     ^
    2 │ var a = 10;
    3 │ 
  

let a = 3;
let a = 10;
code-block.js:2:5 lint/suspicious/noRedeclare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Shouldn't redeclare 'a'. Consider to delete it or rename it.
  
    1 │ let a = 3;
  > 2 │ let a = 10;
      │     ^
    3 │ 
  
  ℹ 'a' is defined here:
  
  > 1 │ let a = 3;
      │     ^
    2 │ let a = 10;
    3 │ 
  

function f() {}
function f() {}
code-block.js:2:10 lint/suspicious/noRedeclare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Shouldn't redeclare 'f'. Consider to delete it or rename it.
  
    1 │ function f() {}
  > 2 │ function f() {}
      │          ^
    3 │ 
  
  ℹ 'f' is defined here:
  
  > 1 │ function f() {}
      │          ^
    2 │ function f() {}
    3 │ 
  

class C {
    static {
        var c = 3;
        var c = 10;
    }
}
code-block.js:4:13 lint/suspicious/noRedeclare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Shouldn't redeclare 'c'. Consider to delete it or rename it.
  
    2 │     static {
    3 │         var c = 3;
  > 4 │         var c = 10;
      │             ^
    5 │     }
    6 │ }
  
  ℹ 'c' is defined here:
  
    1 │ class C {
    2 │     static {
  > 3 │         var c = 3;
      │             ^
    4 │         var c = 10;
    5 │     }
  

type Person = { name: string; }
class Person { name: string; }
code-block.ts:2:7 lint/suspicious/noRedeclare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Shouldn't redeclare 'Person'. Consider to delete it or rename it.
  
    1 │ type Person = { name: string; }
  > 2 │ class Person { name: string; }
      │       ^^^^^^
    3 │ 
  
  ℹ 'Person' is defined here:
  
  > 1 │ type Person = { name: string; }
      │      ^^^^^^
    2 │ class Person { name: string; }
    3 │

Valid

Section titled Valid
var a = 3;
a = 10;
class Foo {
    bar(a: A);
    bar(a: A, b: B);
    bar(a: A, b: B) {}
}
Section titled Related links