Storing it as body IR accomplishes nothing practical over
storing it as source file, i.e. .di files.
except that there's no need to parse source code over and over
again,
which is good for other tools (like completion suggesting,
intelligent
code browsing and so on).
Which usually hold an AST in memory anyway. We have a fast
parser, parsing even a big codebase once is really not a problem,
see DCD for example.
If the only advantage is to skip a parsing stage here or there,
it does not justify the work that would be needed.
