private static bool TopLevelChanged(SyntaxTree oldTree, SourceText oldText, SyntaxTree newTree, SourceText newText)
{
// ** currently, it doesn't do any text based quick check. we can add them later if current logic is not performant enough for typing case.
var change = newText.GetEncompassingTextChangeRange(oldText);
if (change == default(TextChangeRange))
{
// nothing has changed
return false;
}
// if texts are small enough, just use the equivalent to find out whether there was top level edits
if (oldText.Length < MaxTextChangeRangeLength && newText.Length < MaxTextChangeRangeLength)
{
var topLevel = !newTree.IsEquivalentTo(oldTree, topLevel: true);
return topLevel;
}
// okay, text is not small and whole text is changed, then we always treat it as top level edit
if (change.NewLength == newText.Length)
{
return true;
}
// if changes are small enough, we use IsEquivalentTo to find out whether there was a top level edit
if (change.Span.Length < MaxTextChangeRangeLength && change.NewLength < MaxTextChangeRangeLength)
{
var topLevel = !newTree.IsEquivalentTo(oldTree, topLevel: true);
return topLevel;
}
// otherwise, we always consider top level change
return true;
}
