Any time we get the value of Literal, we want to assert that it's actually a
literal. We've been open coding this pattern sporadically throughout the
opcodedispatcher. Let's add an ergonomic helper to fetch the value of literal,
asserting that the value is indeed literal.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Alyssa Rosenzweig
edf1a7970d