syntax_data: {"ast_node_type":"other","tokens":[{"end":63,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             // but who knows what breaks if we change this now.
context_before:             // This still uses `PassMode::Pair` for ScalarPair types. That's unlikely to be intended,
context_after:             if matches!(arg.layout.backend_repr, BackendRepr::Memory { .. }) {