syntax_data: {"ast_node_type":"variable","tokens":[{"end":46,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let Some(first) = fields.next() else {
context_before:         let mut fields = non_zst_fields(cx, layout);
context_after:             // No fields here, so this could be a primitive or enum -- either way it's not a newtype around a thing