private static void VerifyDataFlow(SemanticModel model, DeclarationExpressionSyntax decl, bool isDelegateCreation, bool isExecutableCode, IdentifierNameSyntax[] references, ISymbol symbol)
{
var dataFlowParent = decl.Parent.Parent.Parent as ExpressionSyntax;
if (dataFlowParent == null)
{
Assert.IsAssignableFrom<ConstructorInitializerSyntax>(decl.Parent.Parent.Parent);
return;
}
if (model.IsSpeculativeSemanticModel)
{
Assert.Throws<NotSupportedException>(() => model.AnalyzeDataFlow(dataFlowParent));
return;
}
var dataFlow = model.AnalyzeDataFlow(dataFlowParent);
Assert.Equal(isExecutableCode, dataFlow.Succeeded);
if (isExecutableCode)
{
Assert.True(dataFlow.VariablesDeclared.Contains(symbol, ReferenceEqualityComparer.Instance));
if (!isDelegateCreation)
{
Assert.True(dataFlow.AlwaysAssigned.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.True(dataFlow.WrittenInside.Contains(symbol, ReferenceEqualityComparer.Instance));
var flowsIn = FlowsIn(dataFlowParent, decl, references);
Assert.Equal(flowsIn,
dataFlow.DataFlowsIn.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.Equal(flowsIn,
dataFlow.ReadInside.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.Equal(FlowsOut(dataFlowParent, decl, references),
dataFlow.DataFlowsOut.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.Equal(ReadOutside(dataFlowParent, references),
dataFlow.ReadOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.Equal(WrittenOutside(dataFlowParent, references),
dataFlow.WrittenOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
}
}
}
protected static void VerifyModelForDeclarationField(
SemanticModel model,
SingleVariableDesignationSyntax designation,
bool duplicate,
params IdentifierNameSyntax[] references)
{
var symbol = model.GetDeclaredSymbol(designation);
Assert.Equal(designation.Identifier.ValueText, symbol.Name);
Assert.Equal(SymbolKind.Field, symbol.Kind);
Assert.Equal(designation, symbol.DeclaringSyntaxReferences.Single().GetSyntax());
Assert.Same(symbol, model.GetDeclaredSymbol((SyntaxNode)designation));
var symbols = model.LookupSymbols(designation.SpanStart, name: designation.Identifier.ValueText);
var names = model.LookupNames(designation.SpanStart);
if (duplicate)
{
Assert.True(symbols.Count() > 1);
Assert.Contains(symbol, symbols);
}
else
{
Assert.Same(symbol, symbols.Single());
}
Assert.Contains(designation.Identifier.ValueText, names);
var local = (IFieldSymbol)symbol;
switch (designation.Parent)
{
case DeclarationPatternSyntax decl:
var typeSyntax = decl.Type;
Assert.True(SyntaxFacts.IsInNamespaceOrTypeContext(typeSyntax));
Assert.True(SyntaxFacts.IsInTypeOnlyContext(typeSyntax));
var type = local.Type;
if (typeSyntax.IsVar && type.IsErrorType())
{
Assert.Null(model.GetSymbolInfo(typeSyntax).Symbol);
}
else
{
Assert.Equal(type, model.GetSymbolInfo(typeSyntax).Symbol);
}
AssertTypeInfo(model, decl.Type, type);
break;
case var parent:
Assert.True(parent is VarPatternSyntax);
break;
}
var declarator = designation.Ancestors().OfType <VariableDeclaratorSyntax>().FirstOrDefault();
var inFieldDeclaratorArgumentlist = declarator != null && declarator.Parent.Parent.Kind() != SyntaxKind.LocalDeclarationStatement &&
(declarator.ArgumentList?.Contains(designation)).GetValueOrDefault();
// this is a declaration site, not a use site.
Assert.Null(model.GetSymbolInfo(designation).Symbol);
Assert.Null(model.GetSymbolInfo(designation).Symbol);
foreach (var reference in references)
{
var referenceInfo = model.GetSymbolInfo(reference);
symbols = model.LookupSymbols(reference.SpanStart, name: designation.Identifier.ValueText);
if (duplicate)
{
Assert.Null(referenceInfo.Symbol);
Assert.Contains(symbol, referenceInfo.CandidateSymbols);
Assert.True(symbols.Count() > 1);
Assert.Contains(symbol, symbols);
}
else
{
Assert.Same(symbol, referenceInfo.Symbol);
Assert.Same(symbol, symbols.Single());
Assert.Equal(local.Type, model.GetTypeInfo(reference).Type);
}
Assert.True(model.LookupNames(reference.SpanStart).Contains(designation.Identifier.ValueText));
}
if (!inFieldDeclaratorArgumentlist)
{
var dataFlowParent = designation.FirstAncestorOrSelf <ExpressionSyntax>();
if (model.IsSpeculativeSemanticModel)
{
Assert.Throws <NotSupportedException>(() => model.AnalyzeDataFlow(dataFlowParent));
}
else
{
var dataFlow = model.AnalyzeDataFlow(dataFlowParent);
if (dataFlow.Succeeded)
{
Assert.False(dataFlow.VariablesDeclared.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.AlwaysAssigned.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.WrittenInside.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.DataFlowsIn.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.ReadInside.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.DataFlowsOut.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.ReadOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.WrittenOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
}
}
}
}
private static void VerifyModelForOutField(
SemanticModel model,
DeclarationExpressionSyntax decl,
bool duplicate,
params IdentifierNameSyntax[] references)
{
var variableDesignationSyntax = GetVariableDesignation(decl);
var symbol = model.GetDeclaredSymbol(variableDesignationSyntax);
Assert.Equal(decl.Identifier().ValueText, symbol.Name);
Assert.Equal(SymbolKind.Field, symbol.Kind);
Assert.Equal(variableDesignationSyntax, symbol.DeclaringSyntaxReferences.Single().GetSyntax());
Assert.Same(symbol, model.GetDeclaredSymbol((SyntaxNode)variableDesignationSyntax));
var symbols = model.LookupSymbols(decl.SpanStart, name: decl.Identifier().ValueText);
var names = model.LookupNames(decl.SpanStart);
if (duplicate)
{
Assert.True(symbols.Count() > 1);
Assert.Contains(symbol, symbols);
}
else
{
Assert.Same(symbol, symbols.Single());
}
Assert.Contains(decl.Identifier().ValueText, names);
var local = (FieldSymbol)symbol;
var typeSyntax = decl.Type();
Assert.True(SyntaxFacts.IsInNamespaceOrTypeContext(typeSyntax));
Assert.True(SyntaxFacts.IsInTypeOnlyContext(typeSyntax));
if (typeSyntax.IsVar && local.Type.IsErrorType())
{
Assert.Null(model.GetSymbolInfo(typeSyntax).Symbol);
}
else
{
Assert.Equal(local.Type, model.GetSymbolInfo(typeSyntax).Symbol);
}
var declarator = decl.Ancestors().OfType<VariableDeclaratorSyntax>().FirstOrDefault();
var inFieldDeclaratorArgumentlist = declarator != null && declarator.Parent.Parent.Kind() != SyntaxKind.LocalDeclarationStatement &&
(declarator.ArgumentList?.Contains(decl)).GetValueOrDefault();
if (inFieldDeclaratorArgumentlist)
{
Assert.Null(model.GetSymbolInfo(decl).Symbol);
Assert.Null(model.GetSymbolInfo(decl).Symbol);
}
else
{
Assert.Same(symbol, model.GetSymbolInfo(decl).Symbol);
Assert.Same(symbol, model.GetSymbolInfo(decl).Symbol);
}
Assert.Null(model.GetDeclaredSymbol(decl));
foreach (var reference in references)
{
var referenceInfo = model.GetSymbolInfo(reference);
symbols = model.LookupSymbols(reference.SpanStart, name: decl.Identifier().ValueText);
if (duplicate)
{
Assert.Null(referenceInfo.Symbol);
Assert.Contains(symbol, referenceInfo.CandidateSymbols);
Assert.True(symbols.Count() > 1);
Assert.Contains(symbol, symbols);
}
else
{
Assert.Same(symbol, referenceInfo.Symbol);
Assert.Same(symbol, symbols.Single());
Assert.Equal(local.Type, model.GetTypeInfo(reference).Type);
}
Assert.True(model.LookupNames(reference.SpanStart).Contains(decl.Identifier().ValueText));
}
if (!inFieldDeclaratorArgumentlist)
{
var dataFlowParent = (ExpressionSyntax)decl.Parent.Parent.Parent;
if (model.IsSpeculativeSemanticModel)
{
Assert.Throws<NotSupportedException>(() => model.AnalyzeDataFlow(dataFlowParent));
}
else
{
var dataFlow = model.AnalyzeDataFlow(dataFlowParent);
if (dataFlow.Succeeded)
{
Assert.False(dataFlow.VariablesDeclared.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.AlwaysAssigned.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.WrittenInside.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.DataFlowsIn.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.ReadInside.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.DataFlowsOut.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.ReadOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
Assert.False(dataFlow.WrittenOutside.Contains(symbol, ReferenceEqualityComparer.Instance));
}
}
}
}
public static DataFlowAnalysis AnalyzeDataFlow(this SemanticModel semanticModel, MethodDeclarationSyntax methodDeclarationSyntax)
{
return(semanticModel.AnalyzeDataFlow(methodDeclarationSyntax.Body));
}
private ExpressionSyntax TryVisitInvocationExpression(InvocationExpressionSyntax node, ForEachStatementSyntax containingForEach)
{
var memberAccess = node.Expression as MemberAccessExpressionSyntax;
if (memberAccess != null)
{
var symbol = semantic.GetSymbolInfo(memberAccess).Symbol as IMethodSymbol;
var owner = node.AncestorsAndSelf().FirstOrDefault(x => x is MethodDeclarationSyntax);
if (owner == null)
{
return(null);
}
currentMethodIsStatic = semantic.GetDeclaredSymbol((MethodDeclarationSyntax)owner).IsStatic;
currentMethodName = ((MethodDeclarationSyntax)owner).Identifier.ValueText;
currentMethodTypeParameters = ((MethodDeclarationSyntax)owner).TypeParameterList;
currentMethodConstraintClauses = ((MethodDeclarationSyntax)owner).ConstraintClauses;
if (IsSupportedMethod(GetMethodFullName(node)))
{
var chain = new List <LinqStep>();
chain.Add(new LinqStep(GetMethodFullName(node), node.ArgumentList.Arguments.Select(x => x.Expression).ToList(), node));
var c = node;
var lastNode = node;
while (c.Expression is MemberAccessExpressionSyntax)
{
c = ((MemberAccessExpressionSyntax)c.Expression).Expression as InvocationExpressionSyntax;
if (c != null && IsSupportedMethod(GetMethodFullName(c)))
{
chain.Add(new LinqStep(GetMethodFullName(c), c.ArgumentList.Arguments.Select(x => x.Expression).ToList(), c));
lastNode = c;
}
else
{
break;
}
}
if (containingForEach != null)
{
chain.Insert(0, new LinqStep(IEnumerableForEachMethod, new[] { SyntaxFactory.SimpleLambdaExpression(SyntaxFactory.Parameter(containingForEach.Identifier), containingForEach.Statement) })
{
Lambda = new Lambda(containingForEach.Statement, new[] { CreateParameter(containingForEach.Identifier, semantic.GetTypeInfo(containingForEach.Type).ConvertedType) })
});
}
if (!chain.Any(x => x.Arguments.Any(y => y is AnonymousFunctionExpressionSyntax)))
{
return(null);
}
if (chain.Count == 1 && RootMethodsThatRequireYieldReturn.Contains(chain[0].MethodName))
{
return(null);
}
if (currentMethodName == "SetBlogConfigAsync")
{
Debugger.Break();
}
var flowsIn = new List <ISymbol>();
var flowsOut = new List <ISymbol>();
foreach (var item in chain)
{
foreach (var arg in item.Arguments)
{
if (item.Lambda != null)
{
var dataFlow = semantic.AnalyzeDataFlow(item.Lambda.Body);
var pname = item.Lambda.Parameters.Single().Identifier.ValueText;
foreach (var k in dataFlow.DataFlowsIn)
{
if (k.Name == pname)
{
continue;
}
if (!flowsIn.Contains(k))
{
flowsIn.Add(k);
}
}
foreach (var k in dataFlow.DataFlowsOut)
{
if (k.Name == pname)
{
continue;
}
if (!flowsOut.Contains(k))
{
flowsOut.Add(k);
}
}
}
else
{
var dataFlow = semantic.AnalyzeDataFlow(arg);
foreach (var k in dataFlow.DataFlowsIn)
{
if (!flowsIn.Contains(k))
{
flowsIn.Add(k);
}
}
foreach (var k in dataFlow.DataFlowsOut)
{
if (!flowsOut.Contains(k))
{
flowsOut.Add(k);
}
}
}
}
}
currentFlow = flowsIn
.Union(flowsOut)
.Where(x => (x as IParameterSymbol)?.IsThis != true)
.Select(x => new VariableCapture(x, flowsOut.Contains(x))) ?? Enumerable.Empty <VariableCapture>();
var collection = ((MemberAccessExpressionSyntax)lastNode.Expression).Expression;
if (IsAnonymousType(semantic.GetTypeInfo(collection).Type))
{
return(null);
}
var semanticReturnType = semantic.GetTypeInfo(node).Type;
if (IsAnonymousType(semanticReturnType) || currentFlow.Any(x => IsAnonymousType(GetSymbolType(x.Symbol))))
{
return(null);
}
return(TryRewrite(chain.First().MethodName, collection, semanticReturnType, chain, node)
.WithLeadingTrivia(((CSharpSyntaxNode)containingForEach ?? node).GetLeadingTrivia())
.WithTrailingTrivia(((CSharpSyntaxNode)containingForEach ?? node).GetTrailingTrivia()));
}
}
return(null);
}
private static void Analyze(
SyntaxNodeAnalysisContext context,
SyntaxNode declaration,
ParameterListSyntax parameterList,
CSharpSyntaxNode bodyOrExpressionBody)
{
if (parameterList == null)
{
return;
}
if (bodyOrExpressionBody == null)
{
return;
}
if (!parameterList.Parameters.Any())
{
return;
}
SemanticModel semanticModel = context.SemanticModel;
CancellationToken cancellationToken = context.CancellationToken;
var methodSymbol = (IMethodSymbol)semanticModel.GetDeclaredSymbol(declaration, cancellationToken);
SyntaxWalker walker = null;
foreach (IParameterSymbol parameter in methodSymbol.Parameters)
{
cancellationToken.ThrowIfCancellationRequested();
ITypeSymbol type = parameter.Type;
if (type.Kind == SymbolKind.ErrorType)
{
continue;
}
if (CSharpFacts.IsSimpleType(type.SpecialType))
{
continue;
}
if (!type.IsReadOnlyStruct())
{
if (parameter.RefKind == RefKind.In &&
type.TypeKind == TypeKind.Struct)
{
var parameterSyntax = (ParameterSyntax)parameter.GetSyntax(cancellationToken);
Debug.Assert(parameterSyntax.Modifiers.Contains(SyntaxKind.InKeyword), "");
DiagnosticHelpers.ReportDiagnostic(context, DiagnosticRules.DoNotPassNonReadOnlyStructByReadOnlyReference, parameterSyntax.Identifier);
}
continue;
}
if (parameter.RefKind != RefKind.None)
{
continue;
}
if (walker == null)
{
if (methodSymbol.ImplementsInterfaceMember(allInterfaces: true))
{
break;
}
walker = SyntaxWalker.GetInstance();
}
else if (walker.Parameters.ContainsKey(parameter.Name))
{
walker.Parameters.Clear();
break;
}
walker.Parameters.Add(parameter.Name, parameter);
}
if (walker == null)
{
return;
}
try
{
if (walker.Parameters.Count > 0)
{
walker.SemanticModel = semanticModel;
walker.CancellationToken = cancellationToken;
if (bodyOrExpressionBody.IsKind(SyntaxKind.Block))
{
walker.VisitBlock((BlockSyntax)bodyOrExpressionBody);
}
else
{
walker.VisitArrowExpressionClause((ArrowExpressionClauseSyntax)bodyOrExpressionBody);
}
if (walker.Parameters.Count > 0)
{
DataFlowAnalysis analysis = (bodyOrExpressionBody.IsKind(SyntaxKind.Block))
? semanticModel.AnalyzeDataFlow((BlockSyntax)bodyOrExpressionBody)
: semanticModel.AnalyzeDataFlow(((ArrowExpressionClauseSyntax)bodyOrExpressionBody).Expression);
bool?isReferencedAsMethodGroup = null;
foreach (KeyValuePair <string, IParameterSymbol> kvp in walker.Parameters)
{
var isAssigned = false;
foreach (ISymbol assignedSymbol in analysis.AlwaysAssigned)
{
if (SymbolEqualityComparer.Default.Equals(assignedSymbol, kvp.Value))
{
isAssigned = true;
break;
}
}
if (isAssigned)
{
continue;
}
if (isReferencedAsMethodGroup ??= IsReferencedAsMethodGroup())
{
break;
}
if (kvp.Value.GetSyntaxOrDefault(cancellationToken) is ParameterSyntax parameter)
{
DiagnosticHelpers.ReportDiagnostic(
context,
DiagnosticRules.MakeParameterRefReadOnly,
parameter.Identifier);
}
}
}
}
}
finally
{
SyntaxWalker.Free(walker);
}
bool IsReferencedAsMethodGroup()
{
switch (declaration.Kind())
{
case SyntaxKind.MethodDeclaration:
return(MethodReferencedAsMethodGroupWalker.IsReferencedAsMethodGroup(declaration.Parent, methodSymbol, semanticModel, cancellationToken));
case SyntaxKind.LocalFunctionStatement:
return(MethodReferencedAsMethodGroupWalker.IsReferencedAsMethodGroup(declaration.FirstAncestor <MemberDeclarationSyntax>(), methodSymbol, semanticModel, cancellationToken));
default:
return(false);
}
}
}
// To convert a null-check to pattern-matching, we should make sure of a few things:
//
// (1) The pattern variable may not be used before the point of declaration.
//
// {
// var use = t;
// if (x is T t) {}
// }
//
// (2) The pattern variable may not be used outside of the new scope which
// is determined by the parent statement.
//
// {
// if (x is T t) {}
// }
//
// var use = t;
//
// (3) The pattern variable may not be used before assignment in opposite
// branches, if any.
//
// {
// if (x is T t) {}
// var use = t;
// }
//
// We walk up the tree from the point of null-check and see if any of the above is violated.
private bool CanSafelyConvertToPatternMatching()
{
// Keep track of whether the pattern variable is definitely assigned when false/true.
// We start by the null-check itself, if it's compared with '==', the pattern variable
// will be definitely assigned when false, because we wrap the is-operator in a !-operator.
var defAssignedWhenTrue = _comparison.Kind() == SyntaxKind.NotEqualsExpression;
foreach (var current in _comparison.Ancestors())
{
// Checking for any conditional statement or expression that could possibly
// affect or determine the state of definite-assignment of the pattern variable.
switch (current.Kind())
{
case SyntaxKind.LogicalAndExpression when !defAssignedWhenTrue:
case SyntaxKind.LogicalOrExpression when defAssignedWhenTrue:
// Since the pattern variable is only definitely assigned if the pattern
// succeeded, in the following cases it would not be safe to use pattern-matching.
// For example:
//
// if ((x = o as string) == null && SomeExpression)
// if ((x = o as string) != null || SomeExpression)
//
// Here, x would never be definitely assigned if pattern-matching were used.
return(false);
case SyntaxKind.LogicalAndExpression:
case SyntaxKind.LogicalOrExpression:
// Parentheses and cast expressions do not contribute to the flow analysis.
case SyntaxKind.ParenthesizedExpression:
case SyntaxKind.CastExpression:
// Skip over declaration parts to get to the parenting statement
// which might be a for-statement or a local declaration statement.
case SyntaxKind.EqualsValueClause:
case SyntaxKind.VariableDeclarator:
case SyntaxKind.VariableDeclaration:
continue;
case SyntaxKind.LogicalNotExpression:
// The !-operator negates the definitive assignment state.
defAssignedWhenTrue = !defAssignedWhenTrue;
continue;
case SyntaxKind.ConditionalExpression:
var conditionalExpression = (ConditionalExpressionSyntax)current;
if (LocalFlowsIn(defAssignedWhenTrue
? conditionalExpression.WhenFalse
: conditionalExpression.WhenTrue))
{
// In a conditional expression, the pattern variable
// would not be definitely assigned in the opposite branch.
return(false);
}
return(CheckExpression(conditionalExpression));
case SyntaxKind.ForStatement:
var forStatement = (ForStatementSyntax)current;
if (!forStatement.Condition.Span.Contains(_comparison.Span))
{
// In a for-statement, only the condition expression
// can make this definitely assigned in the loop body.
return(false);
}
return(CheckLoop(forStatement, forStatement.Statement, defAssignedWhenTrue));
case SyntaxKind.WhileStatement:
var whileStatement = (WhileStatementSyntax)current;
return(CheckLoop(whileStatement, whileStatement.Statement, defAssignedWhenTrue));
case SyntaxKind.IfStatement:
var ifStatement = (IfStatementSyntax)current;
var oppositeStatement = defAssignedWhenTrue
? ifStatement.Else?.Statement
: ifStatement.Statement;
if (oppositeStatement != null)
{
var dataFlow = _semanticModel.AnalyzeDataFlow(oppositeStatement);
if (dataFlow.DataFlowsIn.Contains(_localSymbol))
{
// Access before assignment is not safe in the opposite branch
// as the variable is not definitely assgined at this point.
// For example:
//
// if (o is string x) { }
// else { Use(x); }
//
return(false);
}
if (dataFlow.AlwaysAssigned.Contains(_localSymbol))
{
// If the variable is always assigned here, we don't need to check
// subsequent statements as it's definitely assigned afterwards.
// For example:
//
// if (o is string x) { }
// else { x = null; }
//
return(true);
}
}
if (!defAssignedWhenTrue &&
!_semanticModel.AnalyzeControlFlow(ifStatement.Statement).EndPointIsReachable)
{
// Access before assignment here is only valid if we have a negative
// pattern-matching in an if-statement with an unreachable endpoint.
// For example:
//
// if (!(o is string x)) {
// return;
// }
//
// // The 'return' statement above ensures x is definitely assigned here
// Console.WriteLine(x);
//
return(true);
}
return(CheckStatement(ifStatement));
}
switch (current)
{
case ExpressionSyntax expression:
// If we reached here, it means we have a sub-expression that
// does not garantee definite assignment. We should make sure that
// the pattern variable is not used outside of the expression boundaries.
return(CheckExpression(expression));
case StatementSyntax statement:
// If we reached here, it means that the null-check is appeared in
// a statement. In that case, the variable would be actually in the
// scope in subsequent statements, but not definitely assigned.
// Therefore, we should ensure that there is no use before assignment.
return(CheckStatement(statement));
}
// Bail out for error cases and unhandled cases.
break;
}
return(false);
}
private static void ExtractVariableDeclarationsBeforeUsing(SemanticModel semanticModel, List <StatementSyntax> beforeUsing, List <StatementSyntax> insideUsing, List <SyntaxNode> nodesToRemove, CancellationToken ct)
{
var inUsingDataFlow = semanticModel.AnalyzeDataFlow(insideUsing.First(), insideUsing.Last());
var declaredVariablesUsedOutside = inUsingDataFlow.ReadOutside.Union(inUsingDataFlow.WrittenOutside)
.Distinct()
.Intersect(inUsingDataFlow.VariablesDeclared)
.Select(x => new { Symbol = x, Declarator = (VariableDeclaratorSyntax)x.DeclaringSyntaxReferences[0].GetSyntax(ct) })
.ToArray();
for (var i = 0; i < insideUsing.Count; i++)
{
var stmt = insideUsing[i];
var localDeclarationStmt = stmt as LocalDeclarationStatementSyntax;
if (localDeclarationStmt == null)
{
continue;
}
nodesToRemove.Add(localDeclarationStmt);
var declaredVariables = localDeclarationStmt.Declaration
.Variables.Select(x => new { Symbol = semanticModel.GetDeclaredSymbol(x), Declarator = x })
.ToArray();
var variablesToMove = declaredVariables
.Intersect(declaredVariablesUsedOutside)
.ToArray();
if (!variablesToMove.Any())
{
continue;
}
var reducedLocalDeclaration = localDeclarationStmt.RemoveNodes(variablesToMove.Select(x => x.Declarator), SyntaxRemoveOptions.AddElasticMarker);
if (reducedLocalDeclaration.Declaration.Variables.Any())
{
insideUsing[i] = reducedLocalDeclaration;
}
else
{
insideUsing.RemoveAt(i);
i--;
}
foreach (var needAssignment in variablesToMove.Where(x => x.Declarator.Initializer != null))
{
insideUsing.Insert(i + 1, needAssignment.Declarator.InitializerAsAssignment());
}
beforeUsing.Add(SyntaxFactory.LocalDeclarationStatement(
SyntaxFactory.VariableDeclaration(
localDeclarationStmt.Declaration.Type,
SyntaxFactory.SeparatedList(variablesToMove.Select(x => x.Declarator.WithInitializer(null)))
)
)
.WithAdditionalAnnotations(Formatter.Annotation)
);
}
}
private static bool CanBeMadeConst(LocalDeclarationStatementSyntax localDeclaration, SemanticModel semanticModel)
{
// already const?
if (localDeclaration.Modifiers.Any(SyntaxKind.ConstKeyword))
{
return(false);
}
// Ensure that all variables in the local declaration have initializers that
// are assigned with constant values.
foreach (var variable in localDeclaration.Declaration.Variables)
{
var initializer = variable.Initializer;
if (initializer == null)
{
return(false);
}
var constantValue = semanticModel.GetConstantValue(initializer.Value);
if (!constantValue.HasValue)
{
return(false);
}
var variableTypeName = localDeclaration.Declaration.Type;
var variableType = semanticModel.GetTypeInfo(variableTypeName).ConvertedType;
// Ensure that the initializer value can be converted to the type of the
// local declaration without a user-defined conversion.
var conversion = semanticModel.ClassifyConversion(initializer.Value, variableType);
if (!conversion.Exists || conversion.IsUserDefined)
{
return(false);
}
// Special cases:
// * If the constant value is a string, the type of the local declaration
// must be System.String.
// * If the constant value is null, the type of the local declaration must
// be a reference type.
if (constantValue.Value is string)
{
if (variableType.SpecialType != SpecialType.System_String)
{
return(false);
}
}
else if (variableType.IsReferenceType && constantValue.Value != null)
{
return(false);
}
}
// Perform data flow analysis on the local declaration.
var dataFlowAnalysis = semanticModel.AnalyzeDataFlow(localDeclaration);
// Retrieve the local symbol for each variable in the local declaration
// and ensure that it is not written outside of the data flow analysis region.
foreach (var variable in localDeclaration.Declaration.Variables)
{
var variableSymbol = semanticModel.GetDeclaredSymbol(variable);
if (dataFlowAnalysis.WrittenOutside.Contains(variableSymbol))
{
return(false);
}
}
return(true);
}
static bool ContainsLocalReferences(SemanticModel context, SyntaxNode expr, SyntaxNode body)
{
var dataFlowAnalysis = context.AnalyzeDataFlow(expr);
return(dataFlowAnalysis.Captured.Any());
}
private static bool TryGetDataFlowAnalysis(LocalFunctionStatementSyntax localFunction, SemanticModel semanticModel, [NotNullWhen(returnValue: true)] out DataFlowAnalysis?dataFlow)
{
dataFlow = semanticModel.AnalyzeDataFlow(localFunction);
return(dataFlow is { Succeeded : true });
private Diagnostic AnalyzeAwaitedOrReturnedExpression(ExpressionSyntax expressionSyntax, SemanticModel semanticModel, CancellationToken cancellationToken)
{
if (expressionSyntax == null)
{
return(null);
}
if (semanticModel == null)
{
throw new ArgumentNullException(nameof(semanticModel));
}
SymbolInfo symbolToConsider = semanticModel.GetSymbolInfo(expressionSyntax, cancellationToken);
if (CommonInterest.TaskConfigureAwait.Any(configureAwait => configureAwait.IsMatch(symbolToConsider.Symbol)))
{
if (((InvocationExpressionSyntax)expressionSyntax).Expression is MemberAccessExpressionSyntax memberAccessExpression)
{
symbolToConsider = semanticModel.GetSymbolInfo(memberAccessExpression.Expression, cancellationToken);
}
}
ITypeSymbol symbolType;
bool dataflowAnalysisCompatibleVariable = false;
switch (symbolToConsider.Symbol)
{
case ILocalSymbol localSymbol:
symbolType = localSymbol.Type;
dataflowAnalysisCompatibleVariable = true;
break;
case IParameterSymbol parameterSymbol:
symbolType = parameterSymbol.Type;
dataflowAnalysisCompatibleVariable = true;
break;
case IFieldSymbol fieldSymbol:
symbolType = fieldSymbol.Type;
break;
case IMethodSymbol methodSymbol:
if (Utils.IsTask(methodSymbol.ReturnType) && expressionSyntax is InvocationExpressionSyntax invocationExpressionSyntax)
{
// Consider all arguments
var expressionsToConsider = invocationExpressionSyntax.ArgumentList.Arguments.Select(a => a.Expression);
// Consider the implicit first argument when this method is invoked as an extension method.
if (methodSymbol.IsExtensionMethod && invocationExpressionSyntax.Expression is MemberAccessExpressionSyntax invokedMember)
{
if (!methodSymbol.ContainingType.Equals(semanticModel.GetSymbolInfo(invokedMember.Expression, cancellationToken).Symbol))
{
expressionsToConsider = new ExpressionSyntax[] { invokedMember.Expression }.Concat(expressionsToConsider);
}
}
return(expressionsToConsider.Select(e => this.AnalyzeAwaitedOrReturnedExpression(e, semanticModel, cancellationToken)).FirstOrDefault(r => r != null));
}
return(null);
default:
return(null);
}
if (symbolType?.Name != nameof(Task) || !symbolType.BelongsToNamespace(Namespaces.SystemThreadingTasks))
{
return(null);
}
// Report warning if the task was not initialized within the current delegate or lambda expression
var containingFunc = Utils.GetContainingFunction(expressionSyntax);
if (containingFunc.BlockOrExpression is BlockSyntax delegateBlock)
{
if (dataflowAnalysisCompatibleVariable)
{
// Run data flow analysis to understand where the task was defined
DataFlowAnalysis dataFlowAnalysis;
// When possible (await is direct child of the block and not a field), execute data flow analysis by passing first and last statement to capture only what happens before the await
// Check if the await is direct child of the code block (first parent is ExpressionStantement, second parent is the block itself)
if (delegateBlock.Equals(expressionSyntax.Parent.Parent?.Parent))
{
dataFlowAnalysis = semanticModel.AnalyzeDataFlow(delegateBlock.ChildNodes().First(), expressionSyntax.Parent.Parent);
}
else
{
// Otherwise analyze the data flow for the entire block. One caveat: it doesn't distinguish if the initalization happens after the await.
dataFlowAnalysis = semanticModel.AnalyzeDataFlow(delegateBlock);
}
if (!dataFlowAnalysis.WrittenInside.Contains(symbolToConsider.Symbol))
{
return(Diagnostic.Create(Descriptor, expressionSyntax.GetLocation()));
}
}
else
{
// Do the best we can searching for assignment statements.
if (!Utils.IsAssignedWithin(containingFunc.BlockOrExpression, semanticModel, symbolToConsider.Symbol, cancellationToken))
{
return(Diagnostic.Create(Descriptor, expressionSyntax.GetLocation()));
}
}
}
else
{
// It's not a block, it's just a lambda expression, so the variable must be external.
return(Diagnostic.Create(Descriptor, expressionSyntax.GetLocation()));
}
return(null);
}