[cfe-dev] [F18/AST] Using clang tooling with f18

[David Greene via cfe-dev]

> There was a different Flang project before Nvidia's involvement, which
> successfully used and extended Clang ASTs. The code is still on
> Github, along with updated fork (which builds with trunk). It
> implements a fair share of the Fortran features that you have
> mentioned using (what is essentially) Clang's infrastructure.

Thanks for the pointer!  Hopefully we can learn some things from that
project.  It looks like it is still active (last commit three days ago),
but it lacks Fortran 95 support.

> IMO, it is possible to use Clang ASTs, but also there is a lot of
> other code and patterns in Clang that would be useful for a Fortran
> frontend - error handling, driver, testing, etc. It would make sense
> to take those things from Clang rather than reinvent them in F18.

I completely agree.  The goal is to have f18 become an "official" LLVM
project.  In that sense it will be the second frontend to LLVM (I know
about llgo but I don't think there was any attempt at reuse).  There's a
tension between making rapid progress on f18 and reusing clang
components.  Not having worked entensively in either codebase, I don't
have a good sense of how to resolve that tension.

                             -David