public override void Visit(SyntaxNode node)
{
// FIXME How comes a node can be null here?
if (node != null)
{
if (supportedKinds.Contains(node.CSharpKind()))
{
currentBasicBlock.Statements.Add(node);
}
else if (node.IsKind(SyntaxKind.IfStatement))
{
IfStatementSyntax ifNode = (IfStatementSyntax)node;
ControlFlowBasicBlock conditionBasicBlock = currentBasicBlock;
ControlFlowBasicBlock ifTrueBasicBlock = new ControlFlowBasicBlock();
ControlFlowBasicBlock afterIfBasicBlock = new ControlFlowBasicBlock();
conditionBasicBlock.Terminator = ifNode;
Visit(ifNode.Condition);
ifTrueBasicBlock.Successors.Add(afterIfBasicBlock);
SetCurrentBasicBlock(ifTrueBasicBlock);
Visit(ifNode.Statement);
SetCurrentBasicBlock(afterIfBasicBlock);
conditionBasicBlock.Successors.Add(ifTrueBasicBlock);
conditionBasicBlock.Successors.Add(afterIfBasicBlock);
}
else
{
base.Visit(node);
}
}
}
private static void Check(ControlFlowBasicBlock basicBlock, HashSet <ISymbol> nulls, SemanticModel semanticModel, Action <Diagnostic> addDiagnostic)
{
foreach (SyntaxNode node in basicBlock.Statements)
{
if (node.IsKind(SyntaxKind.SimpleAssignmentExpression))
{
BinaryExpressionSyntax statement = (BinaryExpressionSyntax)node;
ISymbol target = semanticModel.GetSymbolInfo(statement.Left).Symbol;
if (target != null)
{
if (IsNull(statement.Right, nulls, semanticModel))
{
nulls.Add(target);
}
else
{
nulls.Remove(target);
}
}
}
else if (node.IsKind(SyntaxKind.ReturnStatement))
{
ReturnStatementSyntax statement = (ReturnStatementSyntax)node;
if (IsNull(statement.Expression, nulls, semanticModel))
{
addDiagnostic(Diagnostic.Create(Rule, statement.GetLocation()));
}
// End of control flow
return;
}
else if (node.IsKind(SyntaxKind.EqualsExpression) || node.IsKind(SyntaxKind.NotEqualsExpression))
{
BinaryExpressionSyntax statement = (BinaryExpressionSyntax)node;
ISymbol target = null;
bool isLeftNull = IsNull(statement.Left, nulls, semanticModel);
bool isRightNull = IsNull(statement.Right, nulls, semanticModel);
if (!isLeftNull && isRightNull)
{
target = semanticModel.GetSymbolInfo(statement.Left).Symbol;
}
else if (isLeftNull && !isRightNull)
{
target = semanticModel.GetSymbolInfo(statement.Right).Symbol;
}
if (target == null)
{
// nothing new was learnt, check both successors using the same state
Check(basicBlock.Successors[0], nulls, semanticModel, addDiagnostic);
Check(basicBlock.Successors[1], nulls, semanticModel, addDiagnostic);
}
else
{
// we're able to learn something new
HashSet <ISymbol> leftNulls = new HashSet <ISymbol>(nulls);
if (statement.IsKind(SyntaxKind.EqualsExpression))
{
leftNulls.Add(target);
}
else
{
leftNulls.Remove(target);
}
HashSet <ISymbol> rightNulls = new HashSet <ISymbol>(nulls);
if (statement.IsKind(SyntaxKind.EqualsExpression))
{
rightNulls.Remove(target);
}
else
{
rightNulls.Add(target);
}
Check(basicBlock.Successors[0], leftNulls, semanticModel, addDiagnostic);
Check(basicBlock.Successors[1], rightNulls, semanticModel, addDiagnostic);
}
}
}
if (basicBlock.Successors.Count == 1)
{
Check(basicBlock.Successors[0], nulls, semanticModel, addDiagnostic);
}
}
private void SetCurrentBasicBlock(ControlFlowBasicBlock newCurrentBasicBlock)
{
basicBlocks.Add(currentBasicBlock);
currentBasicBlock = newCurrentBasicBlock;
}