private static void CheckForBooleanConstant(BinaryExpressionSyntax binaryExpression, ExpressionSyntax booleanContantExpression,
ErrorLocation errorLocation, SyntaxNodeAnalysisContext context, bool leftSide)
{
var expression = leftSide
? binaryExpression.Left
: binaryExpression.Right;
if (!EquivalenceChecker.AreEquivalent(expression.RemoveParentheses(), booleanContantExpression))
{
return;
}
Location location;
switch (errorLocation)
{
case ErrorLocation.Normal:
location = expression.GetLocation();
break;
case ErrorLocation.Extended:
location = CalculateExtendedLocation(binaryExpression, leftSide);
break;
case ErrorLocation.Inverted:
location = CalculateExtendedLocation(binaryExpression, !leftSide);
break;
default:
location = null;
break;
}
context.ReportDiagnosticWhenActive(Diagnostic.Create(rule, location));
}
protected sealed override void Initialize(SonarAnalysisContext context)
{
context.RegisterSyntaxNodeActionInNonGenerated(
c =>
{
var equalsExpression = (BinaryExpressionSyntax)c.Node;
var leftIsNull = EquivalenceChecker.AreEquivalent(equalsExpression.Left, CSharpSyntaxHelper.NullLiteralExpression);
var rightIsNull = EquivalenceChecker.AreEquivalent(equalsExpression.Right, CSharpSyntaxHelper.NullLiteralExpression);
if (!(leftIsNull ^ rightIsNull))
{
return;
}
var expressionToTypeCheck = leftIsNull ? equalsExpression.Right : equalsExpression.Left;
if (c.SemanticModel.GetTypeInfo(expressionToTypeCheck).Type is ITypeParameterSymbol typeInfo &&
!typeInfo.HasReferenceTypeConstraint &&
!typeInfo.ConstraintTypes.OfType <IErrorTypeSymbol>().Any() &&
!typeInfo.ConstraintTypes.Any(typeSymbol =>
typeSymbol.IsReferenceType &&
typeSymbol.IsClass()))
{
var expressionToReportOn = leftIsNull ? equalsExpression.Left : equalsExpression.Right;
c.ReportDiagnosticWhenActive(Diagnostic.Create(rule, expressionToReportOn.GetLocation(),
typeInfo.Name));
}
},
SyntaxKind.EqualsExpression,
SyntaxKind.NotEqualsExpression);
}
private static bool CheckForNullabilityAndBooleanConstantsReport(BinaryExpressionSyntax binaryExpression,
SyntaxNodeAnalysisContext context, bool reportOnTrue)
{
var typeLeft = context.SemanticModel.GetTypeInfo(binaryExpression.Left).Type;
var typeRight = context.SemanticModel.GetTypeInfo(binaryExpression.Right).Type;
var shouldNotReport = IsOnNullableBoolean(typeLeft, typeRight);
if (shouldNotReport)
{
return(true);
}
var binaryExpressionLeft = binaryExpression.Left.RemoveParentheses();
var binaryExpressionRight = binaryExpression.Right.RemoveParentheses();
var leftIsTrue = EquivalenceChecker.AreEquivalent(binaryExpressionLeft, CSharpSyntaxHelper.TrueLiteralExpression);
var leftIsFalse = EquivalenceChecker.AreEquivalent(binaryExpressionLeft, CSharpSyntaxHelper.FalseLiteralExpression);
var rightIsTrue = EquivalenceChecker.AreEquivalent(binaryExpressionRight, CSharpSyntaxHelper.TrueLiteralExpression);
var rightIsFalse = EquivalenceChecker.AreEquivalent(binaryExpressionRight, CSharpSyntaxHelper.FalseLiteralExpression);
var leftIsBoolean = leftIsTrue || leftIsFalse;
var rightIsBoolean = rightIsTrue || rightIsFalse;
if (leftIsBoolean && rightIsBoolean)
{
var bothAreSame = (leftIsTrue && rightIsTrue) || (leftIsFalse && rightIsFalse);
var errorLocation = bothAreSame
? CalculateExtendedLocation(binaryExpression, false)
: CalculateExtendedLocation(binaryExpression, reportOnTrue == leftIsTrue);
context.ReportDiagnosticWhenActive(Diagnostic.Create(rule, errorLocation));
return(true);
}
return(false);
}
private static ExpressionSyntax GetNullCoalescing(ExpressionSyntax whenTrue, ExpressionSyntax whenFalse,
ExpressionSyntax compared, SemanticModel semanticModel, SyntaxAnnotation annotation)
{
if (EquivalenceChecker.AreEquivalent(whenTrue, compared))
{
var createdExpression = SyntaxFactory.BinaryExpression(
SyntaxKind.CoalesceExpression,
compared,
whenFalse)
.WithAdditionalAnnotations(annotation);
return(createdExpression);
}
if (EquivalenceChecker.AreEquivalent(whenFalse, compared))
{
var createdExpression = SyntaxFactory.BinaryExpression(
SyntaxKind.CoalesceExpression,
compared,
whenTrue)
.WithAdditionalAnnotations(annotation);
return(createdExpression);
}
return(GetSimplificationFromInvocations(whenTrue, whenFalse, null, compared, semanticModel, annotation,
isNullCoalescing: true));
}
private static ExpressionSyntax GetSimplifiedAssignment(ExpressionSyntax expression1, ExpressionSyntax expression2,
ExpressionSyntax condition, ExpressionSyntax compared, SemanticModel semanticModel, SyntaxAnnotation annotation,
bool isNullCoalescing)
{
var assignment1 = expression1 as AssignmentExpressionSyntax;
var assignment2 = expression2 as AssignmentExpressionSyntax;
var canBeSimplified =
assignment1 != null &&
assignment2 != null &&
EquivalenceChecker.AreEquivalent(assignment1.Left, assignment2.Left) &&
assignment1.Kind() == assignment2.Kind();
if (!canBeSimplified)
{
return(null);
}
var createdExpression = isNullCoalescing
? GetNullCoalescing(assignment1.Right, assignment2.Right, compared, semanticModel, annotation)
: GetConditionalExpression(condition, assignment1.Right, assignment2.Right, annotation);
return(SyntaxFactory.AssignmentExpression(
assignment1.Kind(),
assignment1.Left,
createdExpression));
}
private static bool CheckValueTypeDefaultValueInitializer(VariableDeclaratorSyntax variable, IFieldSymbol variableSymbol,
SemanticModel semanticModel)
{
if (!variableSymbol.Type.IsValueType)
{
return(false);
}
switch (variableSymbol.Type.SpecialType)
{
case SpecialType.System_Boolean:
return(EquivalenceChecker.AreEquivalent(variable.Initializer.Value, FalseExpression));
case SpecialType.System_Char:
case SpecialType.System_Byte:
case SpecialType.System_Decimal:
case SpecialType.System_Double:
case SpecialType.System_Int16:
case SpecialType.System_Int32:
case SpecialType.System_Int64:
case SpecialType.System_SByte:
case SpecialType.System_Single:
case SpecialType.System_UInt16:
case SpecialType.System_UInt32:
case SpecialType.System_UInt64:
int constantValue;
return(SillyBitwiseOperation.TryGetConstantIntValue(variable.Initializer.Value, out constantValue) &&
constantValue == 0);
default:
return(false);
}
}
public override void Initialize(AnalysisContext context)
{
context.RegisterSyntaxNodeActionInNonGenerated(
c =>
{
var increment = (PostfixUnaryExpressionSyntax)c.Node;
var operatorText = increment.OperatorToken.IsKind(SyntaxKind.PlusPlusToken)
? "increment"
: "decrement";
if (increment.Parent is ReturnStatementSyntax)
{
c.ReportDiagnostic(Diagnostic.Create(Rule, increment.GetLocation(), operatorText));
return;
}
var assignment = increment.Parent as AssignmentExpressionSyntax;
if (assignment != null &&
assignment.IsKind(SyntaxKind.SimpleAssignmentExpression) &&
assignment.Right == increment &&
EquivalenceChecker.AreEquivalent(assignment.Left, increment.Operand))
{
c.ReportDiagnostic(Diagnostic.Create(Rule, increment.GetLocation(), operatorText));
}
},
SyntaxKind.PostIncrementExpression,
SyntaxKind.PostDecrementExpression);
}
private static void CheckLogicalExpression(SyntaxNodeAnalysisContext context)
{
var binaryExpression = (BinaryExpressionSyntax)context.Node;
var left = TryGetBinaryExpression(binaryExpression.Left);
var right = TryGetBinaryExpression(binaryExpression.Right);
if (right == null || left == null)
{
return;
}
var eqRight = EquivalenceChecker.AreEquivalent(right.Right, left.Right);
var eqLeft = EquivalenceChecker.AreEquivalent(right.Left, left.Left);
if (!eqRight || !eqLeft)
{
return;
}
var isEquality = IsIndirectEquality(binaryExpression, right, left, context);
if (isEquality ||
IsIndirectInequality(binaryExpression, right, left, context))
{
var messageEqualityPart = GetMessageEqualityPart(isEquality);
context.ReportDiagnostic(Diagnostic.Create(rule, binaryExpression.GetLocation(), messageEqualityPart));
}
}
private static bool AreCandidateAssignments(ExpressionSyntax expression1, ExpressionSyntax expression2,
ExpressionSyntax compared, SemanticModel semanticModel, bool comparedIsNullInTrue, out bool isNullCoalescing)
{
isNullCoalescing = false;
var assignment1 = expression1 as AssignmentExpressionSyntax;
var assignment2 = expression2 as AssignmentExpressionSyntax;
var canBeSimplified =
assignment1 != null &&
assignment2 != null &&
EquivalenceChecker.AreEquivalent(assignment1.Left, assignment2.Left) &&
assignment1.Kind() == assignment2.Kind();
if (!canBeSimplified)
{
return(false);
}
if (!AreTypesCompatible(assignment1.Right, assignment2.Right, semanticModel))
{
return(false);
}
if (compared != null &&
CanExpressionBeNullCoalescing(assignment1.Right, assignment2.Right, compared, semanticModel, comparedIsNullInTrue))
{
isNullCoalescing = true;
}
return(true);
}
internal static bool TryGetExpressionComparedToNull(ExpressionSyntax expression,
out ExpressionSyntax compared, out bool comparedIsNullInTrue)
{
compared = null;
comparedIsNullInTrue = false;
if (!(expression is BinaryExpressionSyntax binary) ||
!EqualsOrNotEquals.Contains(binary.Kind()))
{
return(false);
}
comparedIsNullInTrue = binary.IsKind(SyntaxKind.EqualsExpression);
if (EquivalenceChecker.AreEquivalent(binary.Left, CSharpSyntaxHelper.NullLiteralExpression))
{
compared = binary.Right;
return(true);
}
if (EquivalenceChecker.AreEquivalent(binary.Right, CSharpSyntaxHelper.NullLiteralExpression))
{
compared = binary.Left;
return(true);
}
return(false);
}
private static bool ContainsExpression(ExecutableStatementSyntax container, ExpressionSyntax contained)
{
return(contained != null &&
container.DescendantNodes()
.OfType <MemberAccessExpressionSyntax>()
.Any(m => m.Expression != null && EquivalenceChecker.AreEquivalent(contained, m.Expression)));
}
internal static bool TryGetComparedVariable(ExpressionSyntax expression,
out ExpressionSyntax compared, out bool comparedIsNullInTrue)
{
compared = null;
comparedIsNullInTrue = false;
var binary = expression as BinaryExpressionSyntax;
if (binary == null ||
!EqualsOrNotEquals.Contains(binary.Kind()))
{
return(false);
}
comparedIsNullInTrue = binary.IsKind(SyntaxKind.EqualsExpression);
if (EquivalenceChecker.AreEquivalent(binary.Left, NullExpression))
{
compared = binary.Right;
return(true);
}
if (EquivalenceChecker.AreEquivalent(binary.Right, NullExpression))
{
compared = binary.Left;
return(true);
}
return(false);
}
private static void CheckConditionalExpression(SyntaxNodeAnalysisContext context)
{
var conditional = (ConditionalExpressionSyntax)context.Node;
var condition = conditional.Condition.RemoveParentheses();
var whenTrue = conditional.WhenTrue.RemoveParentheses();
var whenFalse = conditional.WhenFalse.RemoveParentheses();
if (EquivalenceChecker.AreEquivalent(whenTrue, whenFalse))
{
/// handled by S2758, <see cref="TernaryOperatorPointless"/>
return;
}
ExpressionSyntax comparedToNull;
bool comparedIsNullInTrue;
if (!TryGetExpressionComparedToNull(condition, out comparedToNull, out comparedIsNullInTrue) ||
!ExpressionCanBeNull(comparedToNull, context.SemanticModel))
{
// expression not compared to null, or can't be null
return;
}
if (CanExpressionBeNullCoalescing(whenTrue, whenFalse, comparedToNull, context.SemanticModel, comparedIsNullInTrue))
{
context.ReportDiagnostic(Diagnostic.Create(rule, conditional.GetLocation(), "??"));
}
}
private static void CheckFollowingExpressions(SyntaxNodeAnalysisContext c, int currentExpressionIndex,
List <ExpressionSyntax> expressionsInChain,
ExpressionSyntax expressionComparedToNull, BinaryExpressionSyntax comparisonToNull)
{
for (var j = currentExpressionIndex + 1; j < expressionsInChain.Count; j++)
{
var descendantNodes = expressionsInChain[j].DescendantNodes()
.Where(descendant =>
descendant.IsKind(expressionComparedToNull.Kind()) &&
EquivalenceChecker.AreEquivalent(expressionComparedToNull, descendant))
.Where(descendant =>
(descendant.Parent is MemberAccessExpressionSyntax &&
EquivalenceChecker.AreEquivalent(expressionComparedToNull,
((MemberAccessExpressionSyntax)descendant.Parent).Expression)) ||
(descendant.Parent is ElementAccessExpressionSyntax &&
EquivalenceChecker.AreEquivalent(expressionComparedToNull,
((ElementAccessExpressionSyntax)descendant.Parent).Expression)))
.ToList();
if (descendantNodes.Any())
{
c.ReportDiagnostic(Diagnostic.Create(Rule, comparisonToNull.GetLocation(),
expressionComparedToNull.ToString()));
}
}
}
private static bool IsCompliantCoalesceExpression(ExpressionSyntax parentExpression, AssignmentExpressionSyntax assignment)
{
BinaryExpressionSyntax coalesceExpression;
return(assignment.IsKind(SyntaxKind.SimpleAssignmentExpression) &&
TryGetCoalesceExpressionParent(parentExpression, out coalesceExpression) &&
EquivalenceChecker.AreEquivalent(assignment.Left.RemoveParentheses(), coalesceExpression.Left.RemoveParentheses()));
}
private static void ReportIfExpressionsMatch(SyntaxNodeAnalysisContext context, ExpressionSyntax left, ExpressionSyntax right,
SyntaxToken operatorToken)
{
if (EquivalenceChecker.AreEquivalent(left.RemoveParentheses(), right.RemoveParentheses()))
{
context.ReportDiagnostic(Diagnostic.Create(rule, context.Node.GetLocation(), operatorToken));
}
}
private static void CheckMatchingTests(ExpressionSyntax current, ExpressionSyntax preceding,
SyntaxNodeAnalysisContext c)
{
if (EquivalenceChecker.AreEquivalent(current, preceding))
{
c.ReportDiagnostic(Diagnostic.Create(Rule, current.GetLocation(),
preceding.GetLineNumberToReport()));
}
}
private static bool TwoSidesAreDifferentBooleans(BinaryExpressionSyntax binary)
{
return((
EquivalenceChecker.AreEquivalent(binary.Left, BooleanLiteralUnnecessary.TrueExpression) &&
EquivalenceChecker.AreEquivalent(binary.Right, BooleanLiteralUnnecessary.FalseExpression)) ||
(
EquivalenceChecker.AreEquivalent(binary.Left, BooleanLiteralUnnecessary.FalseExpression) &&
EquivalenceChecker.AreEquivalent(binary.Right, BooleanLiteralUnnecessary.TrueExpression)));
}
private static bool TwoSidesAreSameBooleans(BinaryExpressionSyntax binary)
{
return((
EquivalenceChecker.AreEquivalent(binary.Left, SyntaxHelper.TrueLiteralExpression) &&
EquivalenceChecker.AreEquivalent(binary.Right, SyntaxHelper.TrueLiteralExpression)) ||
(
EquivalenceChecker.AreEquivalent(binary.Left, SyntaxHelper.FalseLiteralExpression) &&
EquivalenceChecker.AreEquivalent(binary.Right, SyntaxHelper.FalseLiteralExpression)));
}
private static void ReportIfExpressionsMatch(SyntaxNodeAnalysisContext context, ExpressionSyntax left, ExpressionSyntax right,
SyntaxToken operatorToken)
{
if (EquivalenceChecker.AreEquivalent(left.RemoveParentheses(), right.RemoveParentheses()))
{
string message = string.Format(OperatorMessageFormat, operatorToken);
context.ReportDiagnosticWhenActive(Diagnostic.Create(rule, context.Node.GetLocation(), message));
}
}
private static void CheckForLoopCondition(SyntaxNodeAnalysisContext context)
{
var forLoop = (ForStatementSyntax)context.Node;
if (forLoop.Condition != null &&
EquivalenceChecker.AreEquivalent(forLoop.Condition.RemoveParentheses(), SyntaxHelper.TrueLiteralExpression))
{
context.ReportDiagnostic(Diagnostic.Create(Rule, forLoop.Condition.GetLocation()));
}
}
private static void CheckLogicalNot(SyntaxNodeAnalysisContext c)
{
var logicalNot = (PrefixUnaryExpressionSyntax)c.Node;
if (EquivalenceChecker.AreEquivalent(logicalNot.Operand, TrueExpression) ||
EquivalenceChecker.AreEquivalent(logicalNot.Operand, FalseExpression))
{
c.ReportDiagnostic(Diagnostic.Create(Rule, logicalNot.Operand.GetLocation()));
}
}
private static void CheckStatement(SyntaxNodeAnalysisContext c, StatementSyntax statementToCheck,
IEnumerable <StatementSyntax> precedingStatements)
{
var precedingStatement = precedingStatements
.FirstOrDefault(preceding => EquivalenceChecker.AreEquivalent(statementToCheck, preceding));
if (precedingStatement != null)
{
ReportStatement(c, statementToCheck, precedingStatement);
}
}
private static void CheckLogicalNot(SyntaxNodeAnalysisContext context)
{
var logicalNot = (PrefixUnaryExpressionSyntax)context.Node;
var logicalNotOperand = logicalNot.Operand.RemoveParentheses();
if (EquivalenceChecker.AreEquivalent(logicalNotOperand, SyntaxHelper.TrueLiteralExpression) ||
EquivalenceChecker.AreEquivalent(logicalNotOperand, SyntaxHelper.FalseLiteralExpression))
{
context.ReportDiagnostic(Diagnostic.Create(Rule, logicalNot.Operand.GetLocation()));
}
}
private static Document RewriteConditional(Document document, SyntaxNode root, SyntaxNode syntaxNode,
ConditionalExpressionSyntax conditional)
{
var whenTrue = conditional.WhenTrue.RemoveParentheses();
if (whenTrue.Equals(syntaxNode) &&
EquivalenceChecker.AreEquivalent(syntaxNode, SyntaxHelper.TrueLiteralExpression))
{
var newRoot = ReplaceExpressionWithBinary(conditional, root,
SyntaxKind.LogicalOrExpression,
conditional.Condition,
conditional.WhenFalse);
return(document.WithSyntaxRoot(newRoot));
}
if (whenTrue.Equals(syntaxNode) &&
EquivalenceChecker.AreEquivalent(syntaxNode, SyntaxHelper.FalseLiteralExpression))
{
var newRoot = ReplaceExpressionWithBinary(conditional, root,
SyntaxKind.LogicalAndExpression,
GetNegatedExpression(conditional.Condition),
conditional.WhenFalse);
return(document.WithSyntaxRoot(newRoot));
}
var whenFalse = conditional.WhenFalse.RemoveParentheses();
if (whenFalse.Equals(syntaxNode) &&
EquivalenceChecker.AreEquivalent(syntaxNode, SyntaxHelper.TrueLiteralExpression))
{
var newRoot = ReplaceExpressionWithBinary(conditional, root,
SyntaxKind.LogicalOrExpression,
GetNegatedExpression(conditional.Condition),
conditional.WhenTrue);
return(document.WithSyntaxRoot(newRoot));
}
if (whenFalse.Equals(syntaxNode) &&
EquivalenceChecker.AreEquivalent(syntaxNode, SyntaxHelper.FalseLiteralExpression))
{
var newRoot = ReplaceExpressionWithBinary(conditional, root,
SyntaxKind.LogicalAndExpression,
conditional.Condition,
conditional.WhenTrue);
return(document.WithSyntaxRoot(newRoot));
}
return(document);
}
private static void CheckStatementsAt(int currentIndex, List <SyntaxList <StatementSyntax> > statements,
SyntaxNodeAnalysisContext context, string constructType)
{
for (int j = 0; j < currentIndex; j++)
{
if (EquivalenceChecker.AreEquivalent(statements[currentIndex], statements[j]))
{
ReportIssue(statements[currentIndex], statements[j], context, constructType);
return;
}
}
}
private static void CheckConditionAt(int currentIndex, List <ExpressionSyntax> conditions, SyntaxNodeAnalysisContext context)
{
for (var j = 0; j < currentIndex; j++)
{
if (EquivalenceChecker.AreEquivalent(conditions[currentIndex], conditions[j]))
{
context.ReportDiagnosticWhenActive(Diagnostic.Create(rule, conditions[currentIndex].GetLocation(),
conditions[j].GetLineNumberToReport()));
return;
}
}
}
protected override void Initialize(SonarAnalysisContext context)
{
context.RegisterSyntaxNodeActionInNonGenerated(
c =>
{
var expression = (AssignmentStatementSyntax)c.Node;
if (EquivalenceChecker.AreEquivalent(expression.Left, expression.Right))
{
c.ReportDiagnostic(Diagnostic.Create(Rule, c.Node.GetLocation()));
}
},
SyntaxKind.SimpleAssignmentStatement);
}
public void AreEquivalent_List()
{
var result = EquivalenceChecker.AreEquivalent(
methods.First(m => m.Identifier.ValueText == "Method1").Body.Statements,
methods.First(m => m.Identifier.ValueText == "Method2").Body.Statements);
result.Should().BeTrue();
result = EquivalenceChecker.AreEquivalent(
methods.First(m => m.Identifier.ValueText == "Method1").Body.Statements,
methods.First(m => m.Identifier.ValueText == "Method3").Body.Statements);
result.Should().BeFalse();
}
public void AreEquivalent_Node()
{
var result = EquivalenceChecker.AreEquivalent(
this.methods.First(m => m.Identifier.ValueText == "Method1").Body,
this.methods.First(m => m.Identifier.ValueText == "Method2").Body);
result.Should().BeTrue();
result = EquivalenceChecker.AreEquivalent(
this.methods.First(m => m.Identifier.ValueText == "Method1").Body,
this.methods.First(m => m.Identifier.ValueText == "Method3").Body);
result.Should().BeFalse();
}
