public virtual SyntaxToken VisitToken(SyntaxToken token)
{
// PERF: This is a hot method, so it has been written to minimize the following:
// 1. Virtual method calls
// 2. Copying of structs
// 3. Repeated null checks
// PERF: Avoid testing node for null more than once
var node = token.Node;
if (node == null)
{
return(token);
}
// PERF: Make one virtual method call each to get the leading and trailing trivia
var leadingTrivia = node.GetLeadingTriviaCore();
var trailingTrivia = node.GetTrailingTriviaCore();
// Trivia is either null or a non-empty list (there's no such thing as an empty green list)
Debug.Assert(leadingTrivia == null || !leadingTrivia.IsList || leadingTrivia.SlotCount > 0);
Debug.Assert(trailingTrivia == null || !trailingTrivia.IsList || trailingTrivia.SlotCount > 0);
if (leadingTrivia != null)
{
// PERF: Expand token.LeadingTrivia when node is not null.
var leading = this.VisitList(new SyntaxTriviaList(token, leadingTrivia));
if (trailingTrivia != null)
{
// Both leading and trailing trivia
// PERF: Expand token.TrailingTrivia when node is not null and leadingTrivia is not null.
// Also avoid node.Width because it makes a virtual call to GetText. Instead use node.FullWidth - trailingTrivia.FullWidth.
var index = leadingTrivia.IsList ? leadingTrivia.SlotCount : 1;
var trailing = this.VisitList(new SyntaxTriviaList(token, trailingTrivia, token.Position + node.FullWidth - trailingTrivia.FullWidth, index));
if (leading.Node != leadingTrivia)
{
token = token.WithLeadingTrivia(leading);
}
return(trailing.Node != trailingTrivia?token.WithTrailingTrivia(trailing) : token);
}
else
{
// Leading trivia only
return(leading.Node != leadingTrivia?token.WithLeadingTrivia(leading) : token);
}
}
else if (trailingTrivia != null)
{
// Trailing trivia only
// PERF: Expand token.TrailingTrivia when node is not null and leading is null.
// Also avoid node.Width because it makes a virtual call to GetText. Instead use node.FullWidth - trailingTrivia.FullWidth.
var trailing = this.VisitList(new SyntaxTriviaList(token, trailingTrivia, token.Position + node.FullWidth - trailingTrivia.FullWidth, index: 0));
return(trailing.Node != trailingTrivia?token.WithTrailingTrivia(trailing) : token);
}
else
{
// No trivia
return(token);
}
}