A chain of `@if` / `@else if` directives is evaluated from top to bottom. At most, only one branch will be executed: the first one with a condition that evaluates to true.

Therefore, duplicating a condition automatically leads to dead code. Usually, this is due to a copy/paste error. At best, it's simply dead code and at worst, it's a bug that is likely to induce further bugs as the code is maintained, and obviously it could lead to unexpected behavior.

## Noncompliant Code Example

    @if $x == 0 {
      do-something();
    } @else if $x == 1 {
      do-something-different();
    } @else if $x == 0 {  /* Noncompliant: Same condition as in the @if directive */
      do-something-else();
    }

## Compliant Solution

    @if $x == 0 {
      do-something();
    } @else if $x == 1 {
      do-something-different();
    } @else if $x == 2 {
      do-something-else();
    }