$border-width-data: (
  base: rem(1px),
  thick: rem(2px),
  thicker: rem(3px),
);

/// Returns the width of the specified border type.
/// @param {String} $variant [base] - The border variant key.
/// @return {Number} The width for the border.

@function border-width($variant: base) {
  $fetched-value: map-get($border-width-data, $variant);

  @if type-of($fetched-value) == number {
    @return $fetched-value;
  } @else {
    @error 'Border width variant `#{$variant}` not found. Available variants: #{available-names($border-width-data)}';
  }
}