void _ValidateExpression(EbnfExpression expr, IDictionary <string, int> refCounts, IList <EbnfMessage> messages)
{
var l = expr as EbnfLiteralExpression;
if (null != l)
{
var i = GetIdForExpression(l);
// don't count itself. only things just like itself
if (null != i && !ReferenceEquals(Productions[i].Expression, l))
{
refCounts[i] += 1;
}
}
var rx = expr as EbnfRegexExpression;
if (null != rx)
{
try
{
FA.Parse(rx.Value);
}
catch (ExpectingException)
{
messages.Add(
new EbnfMessage(
EbnfErrorLevel.Error, 12,
"Invalid regular expression",
expr.Line, expr.Column, expr.Position));
}
var i = GetIdForExpression(rx);
if (null != i && !ReferenceEquals(Productions[i].Expression, l))
{
refCounts[i] += 1;
}
}
var r = expr as EbnfRefExpression;
if (null != r)
{
int rc;
if (null == r.Symbol)
{
messages.Add(
new EbnfMessage(
EbnfErrorLevel.Error, 4,
"Null reference expression",
expr.Line, expr.Column, expr.Position));
return;
}
if (!refCounts.TryGetValue(r.Symbol, out rc))
{
messages.Add(
new EbnfMessage(
EbnfErrorLevel.Error, 1,
string.Concat(
"Reference to undefined symbol \"",
r.Symbol,
"\""),
expr.Line, expr.Column, expr.Position));
return;
}
refCounts[r.Symbol] = rc + 1;
return;
}
var b = expr as EbnfBinaryExpression;
if (null != b)
{
if (null == b.Left && null == b.Right)
{
messages.Add(
new EbnfMessage(
EbnfErrorLevel.Warning, 3,
"Nil expression",
expr.Line, expr.Column, expr.Position));
return;
}
_ValidateExpression(b.Left, refCounts, messages);
_ValidateExpression(b.Right, refCounts, messages);
return;
}
var u = expr as EbnfUnaryExpression;
if (null != u)
{
if (null == u.Expression)
{
messages.Add(
new EbnfMessage(
EbnfErrorLevel.Warning, 3,
"Nil expression",
expr.Line, expr.Column, expr.Position));
return;
}
_ValidateExpression(u.Expression, refCounts, messages);
}
}