[PATCH] D42082: Add DWARF for discriminated unions

[Paul Robinson via Phabricator via llvm-commits]

probinson added a comment.

In https://reviews.llvm.org/D42082#979081, @tromey wrote:

> I think this approach actually makes more sense, because surely the discriminant is something whose placement cannot vary.


But it doesn't.  It's a child of TAG_variant_part, but not under any individual TAG_variant.
That said, I'm happy to support a proposal to move the discriminant's member description out from under TAG_variant_part.  Especially given GCC's practice, which probably is the same for Pascal as it is for Ada.  Semantically it doesn't make any real difference where that member goes.

> I'm thinking now `DW_TAG_Rust_enum` would be a better fit for what I need.  This approach would let me handle univariant enums consistently as well.

I'd argue against a new tag, because it raises the barrier to debugger support for Rust.  I can see wanting to emit all Rust enums consistently, whether they have variant data or not.

How about this:  A Rust enum is implicitly a struct, which has one member in the "univariant" case, and a variant part if it does have additional data.  I'll accept putting the member outside the TAG_variant_part; it's pedantically incorrect but there's a good case for doing it the other way.


Repository:
  rL LLVM

https://reviews.llvm.org/D42082