merge method
Merges this object with other, returning a new object of type T.
Implementation
@override
ContextVariantBuilder merge(ContextVariantBuilder? other) {
if (other == null) return this;
if (other.variant != variant) {
throw ArgumentError.value(other, 'variant is not the same');
}
return ContextVariantBuilder(mergeFn(other.fn), variant);
}