Function parse_property_head 

fn parse_property_head(input: ParseStream<'_>) -> Result<AttrProperty>

Parse a property call head tag(arg0, arg1, ...).

The argument list is parsed position-by-position rather than as a single Expr::Call, because property arguments may be generic types (e.g. ValidTransmute(T, Option<NonZero<T>>)) that syn cannot parse as value expressions.