noSelfAssign (since v12.0.0)
Disallow assignments where both sides are exactly the same.
Self assignments have no effect, so probably those are an error due to incomplete refactoring.
Source: https://eslint.org/docs/latest/rules/no-self-assign
Examples
Invalid
a = a;nursery/noSelfAssign.js:1:5 lint/nursery/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ a is assigned to itself.
> 1 │ a = a;
│ ^
2 │
ℹ This is where is assigned.
> 1 │ a = a;
│ ^
2 │
[a] = [a];nursery/noSelfAssign.js:1:8 lint/nursery/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ a is assigned to itself.
> 1 │ [a] = [a];
│ ^
2 │
ℹ This is where is assigned.
> 1 │ [a] = [a];
│ ^
2 │
({a: b} = {a: b});nursery/noSelfAssign.js:1:15 lint/nursery/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ b is assigned to itself.
> 1 │ ({a: b} = {a: b});
│ ^
2 │
ℹ This is where is assigned.
> 1 │ ({a: b} = {a: b});
│ ^
2 │
a.b = a.b;nursery/noSelfAssign.js:1:9 lint/nursery/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ b is assigned to itself.
> 1 │ a.b = a.b;
│ ^
2 │
ℹ This is where is assigned.
> 1 │ a.b = a.b;
│ ^
2 │
a[b] = a[b];nursery/noSelfAssign.js:1:10 lint/nursery/noSelfAssign ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ b is assigned to itself.
> 1 │ a[b] = a[b];
│ ^
2 │
ℹ This is where is assigned.
> 1 │ a[b] = a[b];
│ ^
2 │
Valid
a &= a;
var a = a;
let a = a;
const a = a;
[a, b] = [b, a];