material-components_material-web/sass/_assert.scss

@use 'sass:meta';

///
/// is-type returns the given value if it matches the given type. If not, it
/// throws an error.
/// @param {*} $val - the value to check the type of.
/// @param {String} $type - the type we expect $val to be.
/// @return {*} returns $val assuming it is of type $type.
///
@function is-type($val, $type) {
  $actual: meta.type-of($val);
  @if $actual != $type {
    @error 'expected "#{$val}" to be of type "#{$type}"; was type "#{$actual}"';
  }
  @return $val;
}