Generated by SassMeister.com.

input.scss

// ----------------------------------------
// emulate mixin-context
// ----------------------------------------
$mixin-context-list: ();
@mixin mixin-context($name){
    $mixin-context-list: append($mixin-context-list, $name, comma) !global;
    @content;
    $mixin-context-list: nth-remove($mixin-context-list, -1) !global; 
}
@function mixin-context(){
    @return $mixin-context-list;
}

// 	helper
@function nth-remove($list, $n){
    $r: ();$n: if($n < 0, length($list) + $n + 1, $n); $b: is-bracketed($list); $s: list-separator($list);
    @for $i from 1 through length($list){ @if $i != $n { $r: append($r, nth($list, $i)); }} 
    @return join((), $r, $s, $b);
}
// ----------------------------------------





// ----------------------------------------
// Mixins
// ----------------------------------------
@mixin button {
	@include mixin-context(button){
		button { 
		    mixin-context: mixin-context();

		    @if index(mixin-context(), log-in){
		    	message: 'login buttons are special';
		    }
		}							
	}
}


@mixin card {
	@include mixin-context(card){
		.card {
			@include button;
		}
	}
}

@mixin collection {
	@include mixin-context(collection){
		.collection {
			@include card;
		}
	}
}


@mixin sign-up {
	@include mixin-context(sign-up){
		.sign-up {
			@include button;
		}
	}
}

@mixin log-in {
	@include mixin-context(log-in){
		.log-in {
			@include button;
		}
	}
}

@mixin modal {
	@include mixin-context(modal){
		.modal {
			@include log-in;
		}
	}
}

@mixin sidebar {
	@include mixin-context(sidebar){
		.sidebar {
			@include collection;
			@include button;	
		}
	}
}

// ----------------------------------------
// Assemble
// ----------------------------------------
@include button;
@include log-in;
@include card;
@include collection;
@include sign-up;
@include sidebar;
@include modal;

output.css

button {
  mixin-context: button;
}

.log-in button {
  mixin-context: log-in, button;
  message: "login buttons are special";
}

.card button {
  mixin-context: card, button;
}

.collection .card button {
  mixin-context: collection, card, button;
}

.sign-up button {
  mixin-context: sign-up, button;
}

.sidebar .collection .card button {
  mixin-context: sidebar, collection, card, button;
}
.sidebar button {
  mixin-context: sidebar, button;
}

.modal .log-in button {
  mixin-context: modal, log-in, button;
  message: "login buttons are special";
}

settings.json

{
  "sass": {
    "compiler": "dart-sass/1.26.11",
    "extensions": {},
    "syntax": "SCSS",
    "outputStyle": "expanded"
  },
  "autoprefixer": false
}