JSON.NodeRule.Object.swift

internal import Grammar

extension JSON.NodeRule {
    /// Matches an object literal.
    ///
    /// Object literals begin and end with curly braces (`{` and `}`), and
    /// contain instances of ``Item`` separated by ``JSON.CommaRule``s.
    /// Trailing commas are not allowed.
    enum Object {
    }
}
extension JSON.NodeRule.Object: ParsingRule {
    typealias Terminal = UInt8

    static func parse<Source>(
        _ input: inout ParsingInput<some ParsingDiagnostics<Source>>
    ) throws -> [(key: JSON.Key, value: JSON.Node)]
        where Source.Index == Location, Source.Element == Terminal {
        try input.parse(as: JSON.BraceLeftRule<Location>.self)
        var items: [(key: JSON.Key, value: JSON.Node)]
        if let head: (key: JSON.Key, value: JSON.Node) = try? input.parse(as: Item.self) {
            items = [head]
            while   let (_, next): (Void, (key: JSON.Key, value: JSON.Node)) = try? input.parse(
                    as: (JSON.CommaRule<Location>, Item).self
                ) {
                items.append(next)
            }
        } else {
            items = []
        }
        try input.parse(as: JSON.BraceRightRule<Location>.self)
        return items
    }
}