global meta issue with spacing function and dart sass

issue.scss

$context--spacing: (0, 2, 4, 8, 16, 24, 32, 48, 64);
$context--keyline-border-color: #ccc;

@function spacing($keys...) {
	@if length($context--spacing) == 0 {
		@error 'No values found in $context--spacing.';
	}

	@if length($keys) > 4 {
		@error 'spacing() accepts a maximum of 4 arguments.';
	}

	$context--spacing-value: ();

	@each $key in $keys {
		@if index($context--spacing, $key) {
			$i: index($context--spacing, $key);

			$context--spacing-value: append($context--spacing-value, nth($context--spacing, $i) * 1px); // Add current item in loop to $context--spacing-value list
		}

		@else {
			@error '#{$key} is not defined in $context--spacing. Permitted values are #{$context--spacing}.';
		}
	}

	// If the length is 1, don't return type 'list'
	// This allows maths operations to be done on a single value. E.g. spacing(12) * 2.
	@if length($context--spacing-value == 1) {
		@return nth($context--spacing-value, 1);
	}
	@else {
		@return $context--spacing-value;
	}
}

@mixin u-keyline($direction: bottom, $spacing: $context--keyline-spacing, $thickness: 1px) {
	$valid-directions: (top, right, bottom, left);

	@if index($valid-directions, $direction) {
		border-#{$direction}: $thickness solid $context--keyline-border-color;
		padding-#{$direction}: spacing($spacing);
		margin-#{$direction}: spacing($spacing);
	}
	@else {
		@warn '$direction should be one of #{$valid-directions}, but was #{$direction}';
	}
}

$meta--keyline-spacing: spacing(8);

.c-meta__item {
	@include u-keyline('right', $meta--keyline-spacing);
}