Refactor clang_getUnqualifiedType (#202)

[TravisCardwell]

Motivation: perform checks in Haskell to take advantage of type safety.

• WrapperResult is completely factored out.
• ClangVersionError is added to indicate version support errors.
• InvalidCXTypeError is added to indicate Haskell-side invalid type errors.
• clang_getUnqualifiedType (Haskell) is refactored to check the libclang version and type validity, removing the checks from wrap_getUnqualifiedType (C).

[TravisCardwell]

Build failures! Interesting. Builds and tests pass locally, and I purposefully made the build fail before changing the C code, so I do not think it is a local cache issue. Investigating...

[edsko]

Build failures! Interesting. Builds and tests pass locally, and I purposefully made the build fail before changing the C code, so I do not think it is a local cache issue. Investigating...

Which OS do you use? On Ubuntu at least it's very easy to have multiple llvm verisons installed (I'm on Ubuntu 24, which supports llvm-14 through llvm-18). I switch between them by having something like this in my .envrc

# export PATH=/usr/lib/llvm-14/bin:$PATH

Not strictly needed, CI will check it anyway, and you'll probably not have to deal with different llvm versions very often anyway, but I thought I'd mention it just in case it's useful.

[TravisCardwell]

I am currently using Arch. llvm14 is available, so I installed it and confirmed that putting the directory at the beginning of my PATH works. Thank you!

Details

$ export PATH=/usr/lib/llvm14/bin:$PATH
$ rm -rf dist-newstyle
$ cabal build all
...
checking for llvm-config... /usr/lib/llvm14/bin/llvm-config
checking LLVM version... 14.0.6
checking LLVM library directory... /usr/lib/llvm14/lib
checking LLVM include directory... /usr/lib/llvm14/include
...

At some point, we might want to test against more versions. Debian has packages for many versions (on different distributions), and it should not be difficult to test locally within containers.

llvm	Version	Distribution
6	6.0.1	buster (oldoldstable)
7	7.0.1	buster (oldoldstable)
9	9.0.1	bullseye (oldstable)
11	11.0.1	bullseye (oldstable)
13	13.0.1	bookworm (stable)
14	14.0.6	bookworm (stable)
15	15.0.6	bookworm (stable)
16	16.0.6	bookworm (stable)
17	17.0.6	sid (unstable)
18	18.1.8	sid (unstable)
19	19.1.1	sid (unstable)
20	20240921	(experimental)

I am not sure what the situation is on Ubuntu, used in CI, as Ubuntu Packages Search is returning internal server errors when searching.

[edsko]

Yes, testing with some older versions especially would be useful, to see if there are any assumptions that we are making that aren't warranted.