/// <summary> /// Decodes an id node using a symbol-to-value mapping. /// An error is reported if the node cannot be decoded. /// </summary> /// <param name="node">A node to decode.</param> /// <param name="decodeMap"> /// A mapping of symbols to values that is used for /// decoding the node. /// </param> /// <param name="enumDescription"> /// A short description of the type of value that is being /// decoded, e.g., "method lookup strategy". /// </param> /// <param name="result"> /// The decoded value, if any. /// </param> /// <returns> /// <c>true</c> if the node could be decoded; otherwise, <c>false</c>. /// </returns> public bool AssertDecodeEnum <T>( LNode node, IReadOnlyDictionary <Symbol, T> decodeMap, string enumDescription, out T result) { if (!node.IsId) { Log.LogSyntaxError( node, FeedbackHelpers.QuoteEven( "expected " + enumDescription + " (", FeedbackHelpers.SpellNodeKind(LNodeKind.Id), " node) but got ", FeedbackHelpers.SpellNodeKind(node), " node.")); result = default(T); return(false); } if (decodeMap.TryGetValue(node.Name, out result)) { return(true); } else { // Create a sorted list of all admissible values. var sortedKeys = new List <string>(); foreach (var item in decodeMap.Keys) { sortedKeys.Add(item.Name); } sortedKeys.Sort(); // Generate a lengthy message that details exactly what // is admissible. var message = new List <MarkupNode>(); message.Add("unknown " + enumDescription + " "); message.Add(node.Name.Name); message.Add("; expected "); for (int i = 0; i < sortedKeys.Count - 1; i++) { message.Add(sortedKeys[i]); if (i < sortedKeys.Count - 2) { message.Add(", "); } else { message.Add(" or "); } } message.Add(sortedKeys[sortedKeys.Count - 1]); message.Add("."); Log.LogSyntaxError( node, FeedbackHelpers.QuoteEven(message.ToArray())); return(false); } }