Generated by SassMeister.com. http://sassmeister.com/gist/2cfc6b7de2ce8591cffb

SassMeister-input.scss

// ----
// Sass (v3.4.13)
// Compass (v1.0.3)
// ----

// 
//  Namespace Collision Detection
//
@function span(){ /* This is not susy */ }
@function last(){ /* This is not susy */ }
@mixin span(){   /* This is not susy */ }

// === Susy get's imported here ===
@mixin _susy-collision-detect {
  //
  // What needs testing
  // Note! alpha will always collide as it is 
  // now part of core Sass 
  //
  $test-collisions:(
    'span', 'gutter', 'container', 'nested', 'global-box-sizing', 'box-sizing',
    'break', 'nobreak', 'first', 'alpha', 'last', 'omega', 'pre', 'push'
  );
  
  //
  // Look for mixins or functions
  //
  $found-collisions:'';
  @for $i from 1 through length($test-collisions){
    $name: nth($test-collisions, $i);
    @if mixin-exists($name){ 
      $found-collisions: $found-collisions + '\A\2022  #{$name} (mixin)';
    }
    @if function-exists($name){ 
      $found-collisions: $found-collisions + '\A\2022  #{$name} (function)';
    }
  }
  
  //
  // Show warning/throw error  
  //
  @if $found-collisions != '' {
    @error('Susy says – we seems to have collisions on the following items:\A#{ $found-collisions }\A\A Please re-map....');
  }
}
@include _susy-collision-detect;

//
//  This is not found as it comes after 
//
@function first(){ /* This is not susy */ }

SassMeister-output.css

Susy says – we seems to have collisions on the following items:

• span (mixin)
• span (function)
• alpha (function)
• last (function)

Please re-map....