Issue 180517.2: Tagless variant parts
Section 5.7.10, pg 123
I'm working on improving the DWARF output of the Rust compiler.
In Rust, an enum is a discriminated union. The compiler supplies
the discriminant. It's possible in Rust to have a unvariant enum,
in which case the compiler omits the discriminant field entirely.
In the Rust compiler (and in LLVM and in gdb) we've chosen to
represent this as a DW_TAG_variant_part that has a single child
(the enum payload), but which does not have a DW_AT_discr member.
I suggest adding text to 5.7.10 allowing this use, for example:
If the variant part does not have a discriminant, then the variant
part should have a single DW_TAG_variant child.
Proposed change conflicts with usage in Pascal and Ada.
Standard allows proposed use case.