Generated by SassMeister.com. http://sassmeister.com/gist/38be6e1459ecabdb2c61

SassMeister-input-HTML.jade

.block
  .block__element
    p Lorem ipsum
    
  .block__element--modifier
    p Lorem ipsum
    
  .block__element.block__element--modifier
    p Lorem ipsum

SassMeister-input.scss

// ----
// Sass (v3.4.7)
// Compass (v1.0.1)
// ----

$module: 'block';

.#{$module} {
  
  &__element {
    color: red;
    
     &--modifier {
      color: green;
    }
  }

  &--modifier {
    .#{$module}__element {
      color: blue;
    }
  }

}

SassMeister-output.css

.block__element {
  color: red;
}
.block__element--modifier {
  color: green;
}
.block--modifier .block__element {
  color: blue;
}

SassMeister-rendered.html

<div class="block">
  <div class="block__element">
    <p>Lorem ipsum</p>
  </div>
  <div class="block__element--modifier">
    <p>Lorem ipsum</p>
  </div>
  <div class="block__element block__element--modifier">
    <p>Lorem ipsum</p>
  </div>
</div>