## Why this should be merged
To be able to generate RLP code using type aliases (defined e.g. in
`coreth`).
This can and should be PR-ed upstream as well I think.
## How this works
Call `types.Unalias()` at the start of `buildContext.makeOp()`. The
alternative of adding a `case` to the switch statement adds unnecessary
recursive calls while `types.Unalias()` is a no-op if not an alias.
## How this was tested
New `rlpgen` unit test with aliases of well-known types that have
special handling—these make their proper handling easy to spot when
inspecting generated code. A recursive alias in the same test also
demonstrates full alias resolution.
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Co-authored-by: Arran Schlosberg <me@arranschlosberg.com>
