Function parse_primary 

fn parse_primary<'a>(
    expr: &'a str,
    decls: &BTreeMap<String, String>,
    stack: &mut Vec<String>,
) -> Result<(ParsedSchema, &'a str, bool), String>

Splits the head of a schema expression from the method chain that follows.

The third element of the tuple says whether the head was the bare z namespace, in which case the first call in the chain is z.object({...}) rather than a modifier. Upstream writes both z.object({...}).passthrough() and, after prettier wraps it, z\n .object({...})\n .passthrough().