private IEnumerable <ISymbol> GetDeclaredSymbolsInTree(
SyntaxTree tree,
Compilation compilation,
Func <SyntaxTree, Compilation, CancellationToken, SemanticModel> getCachedSemanticModel,
CancellationToken cancellationToken)
{
SemanticModel model = getCachedSemanticModel(tree, compilation, cancellationToken);
Text.TextSpan fullSpan = tree.GetRoot(cancellationToken).FullSpan;
List <DeclarationInfo> declarationInfos = new List <DeclarationInfo>();
model.ComputeDeclarationsInSpan(fullSpan, getSymbol: true, builder: declarationInfos, cancellationToken: cancellationToken);
return(declarationInfos.Select(declInfo => declInfo.DeclaredSymbol).Distinct().WhereNotNull());
}