/// <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);
}
}
