Refactorer crashes if the processed code has `derive(PartialEq, Eq)`

[Rua]

Seems to be triggered by CI in #1817:

thread 'main' panicked at 'expected TyKind::Path(qself, path), got Rptr(None, MutTy { ty: Ty { id: NodeId(100617), kind: Path(None, Path { span: Span { lo: BytePos(129373), hi: BytePos(129382), ctxt: #57 }, segments: [PathSegment { ident: C2Rust_Unnamed#0, id: NodeId(100618), args: None }], tokens: None }), span: Span { lo: BytePos(129373), hi: BytePos(129382), ctxt: #57 }, tokens: None }, mutbl: Not })', c2rust-refactor/src/path_edit.rs:127:17