You could implement something like lvalue pattern matching, if you wanted to. Assuming you construct tagged unions like so: Valid 123 Error "Error mes

You could implement something like lvalue pattern matching, if you wanted to. Assuming you construct tagged unions like so: Valid 123 Error "Error message" You could pattern match on the left side of an assignment like so: Valid foo = dosomething() use(foo) Which would extract the wrapped value into 'foo' if the union's tag was 'Valid', or aborted/panicked/did something else somewhat sane if the value didn't match.