Currently LLDB's `ParseRustVariantPart` generates the following
`CXXRecordDecl` for a Rust enum
```rust
enum AA {
A(u8)
}
```
```
CXXRecordDecl 0x5555568d5970 <<invalid sloc>> <invalid sloc> struct AA
|-CXXRecordDecl 0x5555568d5ab0 <<invalid sloc>> <invalid sloc> union test_issue::AA$Inner definition
| |-CXXRecordDecl 0x5555568d5d18 <<invalid sloc>> <invalid sloc> struct A$Variant definition
| | |-DefinitionData pass_in_registers aggregate standard_layout trivially_copyable trivial
| | | `-Destructor simple irrelevant trivial needs_implicit
| | `-FieldDecl 0x555555a77880 <<invalid sloc>> <invalid sloc> value 'test_issue::AA::A'
| `-FieldDecl 0x555555a778f0 <<invalid sloc>> <invalid sloc> $variant$ 'test_issue::AA::test_issue::AA$Inner::A$Variant'
|-CXXRecordDecl 0x5555568d5c48 <<invalid sloc>> <invalid sloc> struct A definition
| `-FieldDecl 0x555555a777e0 <<invalid sloc>> <invalid sloc> __0 'unsigned char'
`-FieldDecl 0x555555a77960 <<invalid sloc>> <invalid sloc> $variants$ 'test_issue::AA::test_issue::AA$Inner'
```
While when the Rust enum type name is the same as its variant name, the
generated `CXXRecordDecl` becomes the following – there's a circular
reference between `struct A$Variant` and `struct A`, causing #163048.
```rust
enum A {
A(u8)
}
```
```
CXXRecordDecl 0x5555568d5760 <<invalid sloc>> <invalid sloc> struct A
|-CXXRecordDecl 0x5555568d58a0 <<invalid sloc>> <invalid sloc> union test_issue::A$Inner definition
| |-CXXRecordDecl 0x5555568d5a38 <<invalid sloc>> <invalid sloc> struct A$Variant definition
| | `-FieldDecl 0x5555568d5b70 <<invalid sloc>> <invalid sloc> value 'test_issue::A' <---- bug here
| `-FieldDecl 0x5555568d5be0 <<invalid sloc>> <invalid sloc> $variant$ 'test_issue::A::test_issue::A$Inner::A$Variant'
`-FieldDecl 0x5555568d5c50 <<invalid sloc>> <invalid sloc> $variants$ 'test_issue::A::test_issue::A$Inner'
```
The problem was caused by `GetUniqueTypeNameAndDeclaration` not
returning the correct qualified name for DWARF DIE `test_issue::A::A`,
instead, it returned `A`. This caused `ParseStructureLikeDIE` to find
the wrong type `test_issue::A` and returned early.
The failure in `GetUniqueTypeNameAndDeclaration` appears to stem from a
language check that returns early unless the language is C++. I changed
it so Rust follows the C++ path rather than returning. I’m not entirely
sure this is the right approach — Rust’s qualified name rules look
similar, but not identical? Alternatively, we could add a Rust-specific
implementation that forms qualified names according to Rust's rules.
bdae26f3b4