`Unrecognized input` error with LESS guarded mixin

See more:

CSS

compilation

LESS

In my LESS project I am having issues getting my guarded mixins working with variables that I declared in another file. Here is the code I am working with:

_defaults.less (contains all of my variables)

//------------------------------------//
//  @INCLUDE
//------------------------------------//
// Set whatever components you want included
// in your project to `true` and any components
// you do not wish to be included to `false`

// Base
@use-main:        true;

_main.less (just a random partial in my project)

.main(@boolean) when (@boolean = true) {
    // Styles go here
}

// Execute mixin
.main(@use-main);

style.less (imports all of my partials)

//------------------------------------//
//  @IMPORTS
//------------------------------------//

// Base styles
@import "base/_main.less";

This is how my project is structured (for around 20 partials that are then imported into the `style.less` file).

Whenever I try to compile my project, I get this error:

> Unrecognised input
> c:\Users\Keenan\Documents\GitHub\project\less\base\_main.less line 1