Hi, Last year there was an effort led by Tom Tromey to add Rust language support into LLDB. He had implemented a fairly complete language plugin, however it was not accepted into mainline because of supportability concerns. I guess these concerns had some merit, because this change did not survive even in Rust's private branch <https://github.com/rust-lang/llvm-project/pull/19> due to the difficulty of rebasing on top of LLVM 9.
I am wondering if there's a more limited version of this, that *can* be merged into mainline: In terms of its memory model, Rust is not that far off from C++, so treating Rust types is if they were C++ types basically works. There is only one major problem: currently LLDB cannot deal with tagged unions, which Rust code uses quite heavily. When such a type is encountered, LLDB just emits an empty struct, which makes it impossible to examine the contents. My tentative proposal is to modify LLDB's DWARFASTParserClang to handle DW_TAG_variant et al, and create a C++ approximation of these types, e.g. as a polymorphic class, or just an untagged union. This would provide at least a minimal level of functionality for Rust (and possibly other languages) and be a much lesser maintenance burden on LLDB core team. What would y'all say?
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