private bool ConversionExists(ExpressionSyntax whenTrue, ExpressionSyntax whenFalse)
{
var whenTrueInfo = SemanticModel.GetTypeInfo(whenTrue);
var whenFalseInfo = SemanticModel.GetTypeInfo(whenFalse);
return(whenTrueInfo.Type != null &&
whenFalseInfo.Type != null &&
SemanticModel.ClassifyConversion(whenFalse, whenTrueInfo.Type).Exists &&
SemanticModel.ClassifyConversion(whenTrue, whenFalseInfo.Type).Exists);
}
private static bool CanRefactor(
SeparatedSyntaxList <ExpressionSyntax> expressions,
ITypeSymbol keyType,
ITypeSymbol valueType,
SemanticModel semanticModel)
{
return(expressions.Count == 2 &&
semanticModel.ClassifyConversion(expressions[0], keyType).IsImplicit &&
semanticModel.ClassifyConversion(expressions[1], valueType).IsImplicit);
}
internal static bool IsExplicitConversion(
this SemanticModel semanticModel,
ExpressionSyntax expression,
ITypeSymbol destinationType,
bool isExplicitInSource = false)
{
if (semanticModel == null)
{
throw new ArgumentNullException(nameof(semanticModel));
}
if (expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if (destinationType == null)
{
throw new ArgumentNullException(nameof(destinationType));
}
if (!destinationType.IsErrorType() &&
!destinationType.IsVoid())
{
Conversion conversion = semanticModel.ClassifyConversion(
expression,
destinationType,
isExplicitInSource);
return(conversion.IsExplicit);
}
return(false);
}
static bool IsDeclarationConstFriendly(LocalDeclarationStatementSyntax declaration, SemanticModel semanticModel)
{
// all variables could be const?
foreach (var variable in declaration.Declaration.Variables)
{
if (variable.Initializer == null)
{
return(false);
}
// is constant
var constantValue = semanticModel.GetConstantValue(variable.Initializer.Value);
var valueIsConstant = constantValue.HasValue;
if (!valueIsConstant)
{
return(false);
}
// if reference type, value is null?
var variableTypeName = declaration.Declaration.Type;
var variableType = semanticModel.GetTypeInfo(variableTypeName).ConvertedType;
if (variableType.IsReferenceType && variableType.SpecialType != SpecialType.System_String && constantValue.Value != null)
{
return(false);
}
// value can be converted to variable type?
var conversion = semanticModel.ClassifyConversion(variable.Initializer.Value, variableType);
if (!conversion.Exists || conversion.IsUserDefined)
{
return(false);
}
}
return(true);
}
private static SyntaxKind GetReplacementKind(
ReturnStatementSyntax returnStatement,
ISymbol containingSymbol,
SemanticModel semanticModel,
CancellationToken cancellationToken)
{
SyntaxToken returnKeyword = returnStatement.ReturnKeyword;
ExpressionSyntax expression = returnStatement.Expression;
if (semanticModel.ContainsCompilerDiagnostic(CSharpErrorCodes.CannotImplicitlyConvertType, expression.Span, cancellationToken))
{
return(SyntaxKind.YieldReturnStatement);
}
else if (semanticModel.ContainsCompilerDiagnostic(CSharpErrorCodes.CannotReturnValueFromIterator, returnKeyword.Span, cancellationToken))
{
ITypeSymbol typeSymbol = semanticModel.GetTypeSymbol(expression, cancellationToken);
containingSymbol = containingSymbol ?? semanticModel.GetEnclosingSymbol(returnStatement.SpanStart, cancellationToken);
if (containingSymbol?.IsKind(SymbolKind.Method) == true)
{
var methodSymbol = (IMethodSymbol)containingSymbol;
ITypeSymbol returnType = methodSymbol.ReturnType;
if (returnType.SpecialType == SpecialType.System_Collections_IEnumerable)
{
if (typeSymbol.IsIEnumerableOrConstructedFromIEnumerableOfT())
{
return(SyntaxKind.ForEachStatement);
}
else
{
return(SyntaxKind.YieldReturnStatement);
}
}
else if (returnType.IsNamedType())
{
var namedTypeSymbol = (INamedTypeSymbol)returnType;
if (namedTypeSymbol.ConstructedFrom.SpecialType == SpecialType.System_Collections_Generic_IEnumerable_T)
{
if (semanticModel
.ClassifyConversion(expression, namedTypeSymbol.TypeArguments[0])
.IsImplicit)
{
return(SyntaxKind.YieldReturnStatement);
}
else
{
return(SyntaxKind.ForEachStatement);
}
}
}
}
}
return(SyntaxKind.None);
}
private static bool AllTypesAreConvertible(SemanticModel semanticModel, ArrayCreationExpressionSyntax arrayCreation, IArrayTypeSymbol arrayType)
{
return(arrayCreation.Initializer.Initializers.All(initializer =>
{
var conversion = semanticModel.ClassifyConversion(initializer, arrayType.ElementType);
return conversion.Exists && (conversion.IsIdentity || conversion.IsWidening);
}));
}
private static bool IsIdentityOrImplicitConversion(
ExpressionSyntax expression,
ITypeSymbol destinationType,
SemanticModel semanticModel)
{
Conversion conversion = semanticModel.ClassifyConversion(expression, destinationType);
return(conversion.IsIdentity ||
conversion.IsImplicit);
}
/// <summary>
/// Checks whether <paramref name="expression" /> is implicitly converted to <see cref="Formula" />.
/// If so, replaces the implicit conversion by an invocation of the corresponding state expression factory method.
/// </summary>
private ExpressionSyntax ReplaceImplicitConversion(ExpressionSyntax expression)
{
if (SemanticModel.GetTypeInfo(expression).Type.IsDerivedFrom(_formulaType))
{
return((ExpressionSyntax)Visit(expression));
}
var conversion = SemanticModel.ClassifyConversion(expression, _formulaType);
if (conversion.IsUserDefined && conversion.IsImplicit)
{
return(CreateInvocation((ExpressionSyntax)Visit(expression)));
}
return((ExpressionSyntax)Visit(expression));
}
public static MyInfo GetTypeInfo2(this SemanticModel model, ExpressionSyntax expression)
{
var typeInfo = ModelExtensions.GetTypeInfo(model, expression);
if (typeInfo.ConvertedType == null)
{
Debug.Write("");
}
var g = new MyInfo
{
Conversion1 = typeInfo.ConvertedType != null
? (Conversion?)model.ClassifyConversion(expression, typeInfo.ConvertedType)
: null,
Conversion2 = model.GetConversion(expression),
TypeInfo = typeInfo
};
return(g);
}
private static bool MightBeConvertibleToInt(ExpressionSyntax expression, SemanticModel semanticModel, out ITypeSymbol type)
{
type = semanticModel.GetTypeInfo(expression).Type;
if (type is IErrorTypeSymbol)
{
return(true);
}
var intType = semanticModel.Compilation.GetTypeByMetadataName("System.Int32");
if (intType == null)
{
return(false);
}
var conversion = semanticModel.ClassifyConversion(expression, intType);
return(conversion.Exists && (conversion.IsIdentity || conversion.IsImplicit));
}
internal static bool IsImplicitConversion(
this SemanticModel semanticModel,
ExpressionSyntax expression,
ITypeSymbol destinationType,
bool isExplicitInSource = false)
{
if (!destinationType.IsErrorType() &&
!destinationType.IsVoid())
{
Conversion conversion = semanticModel.ClassifyConversion(
expression,
destinationType,
isExplicitInSource);
return(conversion.IsImplicit);
}
return(false);
}
private static bool ArgumentsMatchParameters(ArgumentListSyntax argumentList, List <INamedTypeSymbol> argumentTypes,
IMethodSymbol possibleOtherMethod, SemanticModel semanticModel)
{
var methodParameterLookup = new CSharpMethodParameterLookup(argumentList, possibleOtherMethod);
var matchedParameters = new List <IParameterSymbol>();
for (var i = 0; i < argumentList.Arguments.Count; i++)
{
var argument = argumentList.Arguments[i];
var argumentType = argumentTypes[i];
if (!methodParameterLookup.TryGetSymbol(argument, out var parameter))
{
return(false);
}
if (argumentType == null)
{
if (!parameter.Type.IsReferenceType)
{
return(false);
}
}
else
{
var conversion = semanticModel.ClassifyConversion(argument.Expression, parameter.Type);
if (!conversion.IsImplicit)
{
return(false);
}
}
matchedParameters.Add(parameter);
}
var nonMatchedParameters = possibleOtherMethod.Parameters.Except(matchedParameters);
return(nonMatchedParameters.All(p => p.HasExplicitDefaultValue));
}
internal static bool IsImplicitConversion(
this SemanticModel semanticModel,
ExpressionSyntax expression,
ITypeSymbol destinationType,
bool isExplicitInSource = false)
{
if (semanticModel == null)
{
throw new ArgumentNullException(nameof(semanticModel));
}
if (expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if (destinationType == null)
{
throw new ArgumentNullException(nameof(destinationType));
}
if (destinationType.Kind == SymbolKind.ErrorType)
{
return(false);
}
if (destinationType.SpecialType == SpecialType.System_Void)
{
return(false);
}
Conversion conversion = semanticModel.ClassifyConversion(
expression,
destinationType,
isExplicitInSource);
return(conversion.IsImplicit);
}
private static void ChangeTypeAccordingToExpression(
RefactoringContext context,
VariableDeclarationSyntax variableDeclaration,
ITypeSymbol typeSymbol,
SemanticModel semanticModel)
{
foreach (VariableDeclaratorSyntax variableDeclarator in variableDeclaration.Variables)
{
ExpressionSyntax value = variableDeclarator.Initializer?.Value;
if (value == null)
{
return;
}
Conversion conversion = semanticModel.ClassifyConversion(value, typeSymbol);
if (conversion.IsIdentity)
{
return;
}
if (!conversion.IsImplicit)
{
return;
}
}
ITypeSymbol newTypeSymbol = semanticModel.GetTypeSymbol(variableDeclaration.Variables[0].Initializer.Value, context.CancellationToken);
if (newTypeSymbol == null)
{
return;
}
context.RegisterRefactoring(CodeActionFactory.ChangeType(context.Document, variableDeclaration.Type, newTypeSymbol, semanticModel, equivalenceKey: RefactoringIdentifiers.ChangeTypeAccordingToExpression));
}
private static bool CanBeConvertedTo(ExpressionSyntax expression, ITypeSymbol type, SemanticModel model)
{
var conversion = model.ClassifyConversion(expression, type);
return(conversion.Exists && (conversion.IsIdentity || conversion.IsImplicit));
}
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);
}
/// <summary>
/// This method finds all posible const value
/// </summary>
/// <param name="root"><see cref="SyntaxNode"/> in which diagnostics are searched</param>
/// <param name="semanticModel"><see cref="semanticModel"/> which is used to flow analysis</param>
/// <returns>Diagnostics with possible const values</returns>
public static IEnumerable <DiagnosticHelper> FindPossibleConstVariables(this SyntaxNode root,
SemanticModel semanticModel)
=> root.DescendantNodes()
.OfType <LocalDeclarationStatementSyntax>()
.Where(declaration => !declaration.Modifiers.Any(SyntaxKind.ConstKeyword))
.Where(declaration => {
// Retrieve detailed information about the declared type of the local declaration
TypeSyntax variableTypeName = declaration.Declaration.Type;
ITypeSymbol variableType = semanticModel.GetTypeInfo(variableTypeName).ConvertedType;
// Perform data flow analysis on the local declaration.
DataFlowAnalysis dataFlowAnalysis = semanticModel.AnalyzeDataFlow(declaration);
// Retrieve the local symbol for each variable in the local declaration
foreach (VariableDeclaratorSyntax variable in declaration.Declaration.Variables)
{
// Ensure that variable has initializers that are assigned with constant values.
EqualsValueClauseSyntax initializer = variable.Initializer;
if (initializer == null)
{
return(false);
}
var constantValue = semanticModel.GetConstantValue(initializer.Value);
if (!constantValue.HasValue)
{
return(false);
}
// Ensure that the initializer value can be converted to the type of the
// local declaration without a user-defined conversion.
Conversion 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);
}
// Ensure that variable is not written outside of the data flow analysis region.
ISymbol variableSymbol = semanticModel.GetDeclaredSymbol(variable);
if (dataFlowAnalysis.WrittenOutside.Contains(variableSymbol))
{
return(false);
}
}
// Finally, it can be const
return(true);
})
.Select(declaration => DiagnosticHelper.Create(declaration, "Variable can be const",
new AddConstModifier(semanticModel)));
protected override Conversion ClassifyConversion(SemanticModel model, ExpressionSyntax expression, ITypeSymbol targetType) => model.ClassifyConversion(expression, targetType);
public static bool IsUnnecessaryCast(this CastExpressionSyntax cast, SemanticModel semanticModel, CancellationToken cancellationToken)
{
var speculationAnalyzer = new SpeculationAnalyzer(cast,
cast.Expression, semanticModel, cancellationToken,
skipVerificationForReplacedNode: true, failOnOverloadResolutionFailuresInOriginalCode: true);
// First, check to see if the node ultimately parenting this cast has any
// syntax errors. If so, we bail.
if (speculationAnalyzer.SemanticRootOfOriginalExpression.ContainsDiagnostics)
{
return(false);
}
var castTypeInfo = semanticModel.GetTypeInfo(cast, cancellationToken);
var castType = castTypeInfo.Type;
// Case:
// 1 . Console.WriteLine(await (dynamic)task); Any Dynamic Cast will not be removed.
if (castType == null || castType.Kind == SymbolKind.DynamicType || castType.IsErrorType())
{
return(false);
}
var expressionTypeInfo = semanticModel.GetTypeInfo(cast.Expression, cancellationToken);
var expressionType = expressionTypeInfo.Type;
// We do not remove any cast on
// 1. Dynamic Expressions
// 2. If there is any other argument which is dynamic
// 3. Dynamic Invocation
if ((expressionType != null &&
(expressionType.IsErrorType() ||
expressionType.Kind == SymbolKind.DynamicType)) ||
IsDynamicInvocation(cast, semanticModel, cancellationToken))
{
return(false);
}
if (PointerCastDefinitelyCantBeRemoved(cast))
{
return(false);
}
if (CastPassedToParamsArrayDefinitelyCantBeRemoved(cast, castType, semanticModel, cancellationToken))
{
return(false);
}
if (speculationAnalyzer.ReplacementChangesSemantics())
{
return(false);
}
var expressionToCastType = semanticModel.ClassifyConversion(cast.SpanStart, cast.Expression, castType, isExplicitInSource: true);
bool parentIsOrAsExpression;
var outerType = GetOuterCastType(cast, semanticModel, out parentIsOrAsExpression) ?? castTypeInfo.ConvertedType;
// Simple case: If the conversion from the inner expression to the cast type is identity,
// the cast can be removed.
if (expressionToCastType.IsIdentity)
{
// Required explicit cast for reference comparison.
// Cast removal causes warning CS0252 (Possible unintended reference comparison).
// object x = string.Intern("Hi!");
// (object)x == "Hi!"
ExpressionSyntax other;
if (IsRequiredCastForReferenceEqualityComparison(outerType, cast, semanticModel, out other))
{
var otherToOuterType = semanticModel.ClassifyConversion(other, outerType);
if (otherToOuterType.IsImplicit && otherToOuterType.IsReference)
{
return(false);
}
}
return(true);
}
if (parentIsOrAsExpression)
{
// Note: speculationAnalyzer.ReplacementChangesSemantics() ensures that the parenting is or as expression are not broken.
// Here we just need to ensure that the original cast expression doesn't invoke a user defined operator.
return(!expressionToCastType.IsUserDefined);
}
if (outerType != null)
{
var castToOuterType = semanticModel.ClassifyConversion(cast.SpanStart, cast, outerType);
var expressionToOuterType = GetSpeculatedExpressionToOuterTypeConversion(speculationAnalyzer.ReplacedExpression, speculationAnalyzer, cancellationToken);
// CONSIDER: Anonymous function conversions cannot be compared from different semantic models as lambda symbol comparison requires syntax tree equality. Should this be a compiler bug?
// For now, just revert back to computing expressionToOuterType using the original semantic model.
if (expressionToOuterType.IsAnonymousFunction)
{
expressionToOuterType = semanticModel.ClassifyConversion(cast.SpanStart, cast.Expression, outerType);
}
// If there is an user-defined conversion from the expression to the cast type or the cast
// to the outer type, we need to make sure that the same user-defined conversion will be
// called if the cast is removed.
if (castToOuterType.IsUserDefined || expressionToCastType.IsUserDefined)
{
return(!expressionToOuterType.IsExplicit &&
(HaveSameUserDefinedConversion(expressionToCastType, expressionToOuterType) ||
HaveSameUserDefinedConversion(castToOuterType, expressionToOuterType)) &&
UserDefinedConversionIsAllowed(cast, semanticModel));
}
else if (expressionToOuterType.IsUserDefined)
{
return(false);
}
if (expressionToCastType.IsExplicit &&
expressionToOuterType.IsExplicit)
{
return(false);
}
// Required explicit cast for reference comparison.
// Cast removal causes warning CS0252 (Possible unintended reference comparison).
// object x = string.Intern("Hi!");
// x == (object)"Hi!"
ExpressionSyntax other;
if (expressionToCastType.IsImplicit && expressionToCastType.IsReference &&
castToOuterType.IsIdentity &&
IsRequiredCastForReferenceEqualityComparison(outerType, cast, semanticModel, out other))
{
return(false);
}
// If the conversion from the expression to the cast type is implicit numeric or constant
// and the conversion from the expression to the outer type is identity, we'll go ahead
// and remove the cast.
if (expressionToOuterType.IsIdentity &&
expressionToCastType.IsImplicit &&
(expressionToCastType.IsNumeric || expressionToCastType.IsConstantExpression))
{
return(true);
}
if (!castToOuterType.IsBoxing &&
castToOuterType == expressionToOuterType)
{
if (castToOuterType.IsNullable)
{
// Even though both the nullable conversions (castToOuterType and expressionToOuterType) are equal, we can guarantee no data loss only if there is an
// implicit conversion from expression type to cast type and expression type is non-nullable. For example, consider the cast removal "(float?)" for below:
// Console.WriteLine((int)(float?)(int?)2147483647); // Prints -2147483648
// castToOuterType: ExplicitNullable
// expressionToOuterType: ExplicitNullable
// expressionToCastType: ImplicitNullable
// We should not remove the cast to "float?".
// However, cast to "int?" is unnecessary and should be removable.
return(expressionToCastType.IsImplicit && ((ITypeSymbol)expressionType.OriginalDefinition).SpecialType != SpecialType.System_Nullable_T);
}
else if (expressionToCastType.IsImplicit && expressionToCastType.IsNumeric && !castToOuterType.IsIdentity)
{
// Some implicit numeric conversions can cause loss of precision and must not be removed.
return(!IsRequiredImplicitNumericConversion(expressionType, castType));
}
return(true);
}
if (castToOuterType.IsIdentity &&
!expressionToCastType.IsUnboxing &&
expressionToCastType == expressionToOuterType)
{
return(true);
}
// Special case: It's possible to have useless casts inside delegate creation expressions.
// For example: new Func<string, bool>((Predicate<object>)(y => true)).
if (IsInDelegateCreationExpression(cast, semanticModel))
{
if (expressionToCastType.IsAnonymousFunction && expressionToOuterType.IsAnonymousFunction)
{
return(!speculationAnalyzer.ReplacementChangesSemanticsOfUnchangedLambda(cast.Expression, speculationAnalyzer.ReplacedExpression));
}
if (expressionToCastType.IsMethodGroup && expressionToOuterType.IsMethodGroup)
{
return(true);
}
}
// Case :
// 1. IList<object> y = (IList<dynamic>)new List<object>()
if (expressionToCastType.IsExplicit && castToOuterType.IsExplicit && expressionToOuterType.IsImplicit)
{
return(true);
}
// Case :
// 2. object y = (ValueType)1;
if (expressionToCastType.IsBoxing && expressionToOuterType.IsBoxing && castToOuterType.IsImplicit)
{
return(true);
}
// Case :
// 3. object y = (NullableValueType)null;
if ((!castToOuterType.IsBoxing || expressionToCastType.IsNullLiteral) &&
castToOuterType.IsImplicit &&
expressionToCastType.IsImplicit &&
expressionToOuterType.IsImplicit)
{
if (expressionToOuterType.IsAnonymousFunction)
{
return(expressionToCastType.IsAnonymousFunction &&
!speculationAnalyzer.ReplacementChangesSemanticsOfUnchangedLambda(cast.Expression, speculationAnalyzer.ReplacedExpression));
}
return(true);
}
// case :
// 4. baseType x;
// baseType y = (DerivedType)x;
if (expressionToOuterType.IsIdentity &&
castToOuterType.IsImplicit &&
castToOuterType.IsReference)
{
return(true);
}
}
return(false);
}
internal static bool?TryFindFirstMisMatch(ImmutableArray <IParameterSymbol> parameters, ImmutableArray <ExpressionSyntax> values, SemanticModel semanticModel, CancellationToken cancellationToken, out ExpressionSyntax?expression)
{
if (parameters.IsEmpty &&
!values.IsEmpty)
{
expression = null;
return(true);
}
if (parameters.TryFirst(x => x.RefKind == RefKind.Ref || x.RefKind == RefKind.Out, out _))
{
expression = null;
return(null);
}
if (values.Length != parameters.Length)
{
if (parameters.TryLast(out var last) &&
!last.IsParams)
{
expression = null;
return(true);
}
if (values.Length < parameters.Length - 1)
{
expression = null;
return(true);
}
}
IParameterSymbol?lastParameter = null;
for (var i = 0; i < values.Length; i++)
{
expression = values[i];
if (lastParameter is null ||
!lastParameter.IsParams)
{
if (!parameters.TryElementAt(i, out lastParameter))
{
return(true);
}
}
if (lastParameter.IsOptional &&
semanticModel.TryGetSymbol(values[i], cancellationToken, out IFieldSymbol? field) &&
field == KnownSymbol.Missing.Value)
{
continue;
}
if (IsNull(values[i]))
{
if (lastParameter.IsParams)
{
return(true);
}
continue;
}
var conversion = semanticModel.ClassifyConversion(values[i], lastParameter.Type);
if (!conversion.Exists)
{
if (lastParameter.Type is IArrayTypeSymbol arrayType &&
semanticModel.ClassifyConversion(values[i], arrayType.ElementType).IsIdentity)
{
continue;
}
return(true);
}
if (conversion.IsIdentity || conversion.IsImplicit)
{
if (values[i] is MemberAccessExpressionSyntax memberAccess &&
memberAccess.Name.Identifier.ValueText == "Value" &&
semanticModel.TryGetSymbol(values[i], cancellationToken, out field) &&
field == KnownSymbol.Missing.Value)
{
return(true);
}
continue;
}
if (conversion.IsExplicit &&
conversion.IsReference)
{
continue;
}
return(true);
}
expression = null;
return(false);
private static void AssertInfoForDeclarationExpressionSyntax(SemanticModel model, DeclarationExpressionSyntax decl)
{
var symbolInfo = model.GetSymbolInfo(decl);
Assert.Null(symbolInfo.Symbol);
Assert.Empty(symbolInfo.CandidateSymbols);
Assert.Equal(CandidateReason.None, symbolInfo.CandidateReason);
Assert.Equal(symbolInfo, ((CSharpSemanticModel)model).GetSymbolInfo(decl));
var typeInfo = model.GetTypeInfo(decl);
Assert.Null(typeInfo.Type);
Assert.Null(typeInfo.ConvertedType);
Assert.Equal(typeInfo, ((CSharpSemanticModel)model).GetTypeInfo(decl));
var conversion = model.ClassifyConversion(decl, model.Compilation.ObjectType, false);
Assert.False(conversion.Exists);
Assert.Equal(conversion, model.ClassifyConversion(decl, model.Compilation.ObjectType, true));
Assert.Equal(conversion, ((CSharpSemanticModel)model).ClassifyConversion(decl, model.Compilation.ObjectType, false));
Assert.Equal(conversion, ((CSharpSemanticModel)model).ClassifyConversion(decl, model.Compilation.ObjectType, true));
Assert.Equal(conversion, model.ClassifyConversion(decl.Position, decl, model.Compilation.ObjectType, false));
Assert.Equal(conversion, model.ClassifyConversion(decl.Position, decl, model.Compilation.ObjectType, true));
Assert.Equal(conversion, ((CSharpSemanticModel)model).ClassifyConversion(decl.Position, decl, model.Compilation.ObjectType, false));
Assert.Equal(conversion, ((CSharpSemanticModel)model).ClassifyConversion(decl.Position, decl, model.Compilation.ObjectType, true));
Assert.Null(model.GetDeclaredSymbol(decl));
}
private void ConversionTestHelper(SemanticModel semanticModel, ExpressionSyntax expr, ITypeSymbol expsym, ConversionKind expkind)
{
var info = semanticModel.GetTypeInfo(expr);
Assert.NotNull(info);
Assert.NotNull(info.ConvertedType);
// NOT expect NoConversion
Conversion act1 = semanticModel.ClassifyConversion(expr, expsym);
Assert.Equal(expkind, act1.Kind);
ValidateConversion(act1, expkind);
}
public override bool CanImplicitlyConvert(SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol targetType)
{
return(syntax is ExpressionSyntax expressionSyntax &&
semanticModel.ClassifyConversion(expressionSyntax, targetType).IsImplicit);
}
protected override bool CanBeConvertedTo(ExpressionSyntax expression, ITypeSymbol type, SemanticModel semanticModel)
{
var conversion = semanticModel.ClassifyConversion(expression, type);
return(conversion.Exists && (conversion.IsIdentity || conversion.IsImplicit));
}
private bool IsArgumentExceptionType(TypeSyntax typeSyntax)
{
var conversion = _semanticModel.ClassifyConversion(typeSyntax, _argumentExceptionType);
return(conversion.IsReference && conversion.IsImplicit);
}
private static bool IsUnnecessaryCast(
ExpressionSyntax castNode, ExpressionSyntax castedExpressionNode,
SemanticModel semanticModel, CancellationToken cancellationToken)
{
var speculationAnalyzer = new SpeculationAnalyzer(castNode,
castedExpressionNode, semanticModel, cancellationToken,
skipVerificationForReplacedNode: true, failOnOverloadResolutionFailuresInOriginalCode: true);
// First, check to see if the node ultimately parenting this cast has any
// syntax errors. If so, we bail.
if (speculationAnalyzer.SemanticRootOfOriginalExpression.ContainsDiagnostics)
{
return(false);
}
var castTypeInfo = semanticModel.GetTypeInfo(castNode, cancellationToken);
var castType = castTypeInfo.Type;
// Case:
// 1 . Console.WriteLine(await (dynamic)task); Any Dynamic Cast will not be removed.
if (castType == null || castType.Kind == SymbolKind.DynamicType || castType.IsErrorType())
{
return(false);
}
var expressionTypeInfo = semanticModel.GetTypeInfo(castedExpressionNode, cancellationToken);
var expressionType = expressionTypeInfo.Type;
if (EnumCastDefinitelyCantBeRemoved(castNode, expressionType, castType))
{
return(false);
}
// We do not remove any cast on
// 1. Dynamic Expressions
// 2. If there is any other argument which is dynamic
// 3. Dynamic Invocation
// 4. Assignment to dynamic
if ((expressionType != null &&
(expressionType.IsErrorType() ||
expressionType.Kind == SymbolKind.DynamicType)) ||
IsDynamicInvocation(castNode, semanticModel, cancellationToken) ||
IsDynamicAssignment(castNode, semanticModel, cancellationToken))
{
return(false);
}
if (PointerCastDefinitelyCantBeRemoved(castNode, castedExpressionNode))
{
return(false);
}
if (CastPassedToParamsArrayDefinitelyCantBeRemoved(castNode, castType, semanticModel, cancellationToken))
{
return(false);
}
// A casts to object can always be removed from an expression inside of an interpolation, since it'll be converted to object
// in order to call string.Format(...) anyway.
if (castType?.SpecialType == SpecialType.System_Object &&
castNode.WalkUpParentheses().IsParentKind(SyntaxKind.Interpolation))
{
return(true);
}
if (speculationAnalyzer.ReplacementChangesSemantics())
{
return(false);
}
var expressionToCastType = semanticModel.ClassifyConversion(castNode.SpanStart, castedExpressionNode, castType, isExplicitInSource: true);
var outerType = GetOuterCastType(castNode, semanticModel, out var parentIsOrAsExpression) ?? castTypeInfo.ConvertedType;
// Simple case: If the conversion from the inner expression to the cast type is identity,
// the cast can be removed.
if (expressionToCastType.IsIdentity)
{
// Simple case: Is this an identity cast to another cast? If so, we're safe to remove it.
if (castedExpressionNode.WalkDownParentheses().IsKind(SyntaxKind.CastExpression))
{
return(true);
}
// Required explicit cast for reference comparison.
// Cast removal causes warning CS0252 (Possible unintended reference comparison).
// object x = string.Intern("Hi!");
// (object)x == "Hi!"
if (IsRequiredCastForReferenceEqualityComparison(outerType, castNode, semanticModel, out var other))
{
var otherToOuterType = semanticModel.ClassifyConversion(other, outerType);
if (otherToOuterType.IsImplicit && otherToOuterType.IsReference)
{
return(false);
}
}
if (SameSizedFloatingPointCastMustBePreserved(
semanticModel, castNode, castedExpressionNode,
expressionType, castType, cancellationToken))
{
return(false);
}
return(true);
}
Debug.Assert(!expressionToCastType.IsIdentity);
if (expressionToCastType.IsExplicit)
{
// Explicit reference conversions can cause an exception or data loss, hence can never be removed.
if (expressionToCastType.IsReference)
{
return(false);
}
// Unboxing conversions can cause a null ref exception, hence can never be removed.
if (expressionToCastType.IsUnboxing)
{
return(false);
}
// Don't remove any explicit numeric casts.
// https://github.com/dotnet/roslyn/issues/2987 tracks improving on this conservative approach.
if (expressionToCastType.IsNumeric)
{
return(false);
}
}
if (expressionToCastType.IsPointer || expressionToCastType.IsIntPtr)
{
// Don't remove any non-identity pointer or IntPtr conversions.
// https://github.com/dotnet/roslyn/issues/2987 tracks improving on this conservative approach.
return(expressionType != null && expressionType.Equals(outerType));
}
if (expressionToCastType.IsInterpolatedString)
{
// interpolation casts are necessary to preserve semantics if our destination type is not itself
// FormattableString or some interface of FormattableString.
return(castType.Equals(castTypeInfo.ConvertedType) ||
ImmutableArray <ITypeSymbol> .CastUp(castType.AllInterfaces).Contains(castTypeInfo.ConvertedType));
}
if (castedExpressionNode.WalkDownParentheses().IsKind(SyntaxKind.DefaultLiteralExpression) &&
!castType.Equals(outerType) &&
outerType.IsNullable())
{
// We have a cast like `(T?)(X)default`. We can't remove the inner cast as it effects what value
// 'default' means in this context.
return(false);
}
if (parentIsOrAsExpression)
{
// Note: speculationAnalyzer.ReplacementChangesSemantics() ensures that the parenting is or as expression are not broken.
// Here we just need to ensure that the original cast expression doesn't invoke a user defined operator.
return(!expressionToCastType.IsUserDefined);
}
if (outerType != null)
{
var castToOuterType = semanticModel.ClassifyConversion(castNode.SpanStart, castNode, outerType);
var expressionToOuterType = GetSpeculatedExpressionToOuterTypeConversion(speculationAnalyzer.ReplacedExpression, speculationAnalyzer, cancellationToken);
// if the conversion to the outer type doesn't exist, then we shouldn't offer, except for anonymous functions which can't be reasoned about the same way (see below)
if (!expressionToOuterType.Exists && !expressionToOuterType.IsAnonymousFunction)
{
return(false);
}
// CONSIDER: Anonymous function conversions cannot be compared from different semantic models as lambda symbol comparison requires syntax tree equality. Should this be a compiler bug?
// For now, just revert back to computing expressionToOuterType using the original semantic model.
if (expressionToOuterType.IsAnonymousFunction)
{
expressionToOuterType = semanticModel.ClassifyConversion(castNode.SpanStart, castedExpressionNode, outerType);
}
// If there is an user-defined conversion from the expression to the cast type or the cast
// to the outer type, we need to make sure that the same user-defined conversion will be
// called if the cast is removed.
if (castToOuterType.IsUserDefined || expressionToCastType.IsUserDefined)
{
return(!expressionToOuterType.IsExplicit &&
(HaveSameUserDefinedConversion(expressionToCastType, expressionToOuterType) ||
HaveSameUserDefinedConversion(castToOuterType, expressionToOuterType)) &&
UserDefinedConversionIsAllowed(castNode, semanticModel));
}
else if (expressionToOuterType.IsUserDefined)
{
return(false);
}
if (expressionToCastType.IsExplicit &&
expressionToOuterType.IsExplicit)
{
return(false);
}
// Required explicit cast for reference comparison.
// Cast removal causes warning CS0252 (Possible unintended reference comparison).
// object x = string.Intern("Hi!");
// x == (object)"Hi!"
if (expressionToCastType.IsImplicit && expressionToCastType.IsReference &&
castToOuterType.IsIdentity &&
IsRequiredCastForReferenceEqualityComparison(outerType, castNode, semanticModel, out var other))
{
return(false);
}
// If the conversion from the expression to the cast type is implicit numeric or constant
// and the conversion from the expression to the outer type is identity, we'll go ahead
// and remove the cast.
if (expressionToOuterType.IsIdentity &&
expressionToCastType.IsImplicit &&
(expressionToCastType.IsNumeric || expressionToCastType.IsConstantExpression))
{
// Some implicit numeric conversions can cause loss of precision and must not be removed.
return(!IsRequiredImplicitNumericConversion(expressionType, castType));
}
if (!castToOuterType.IsBoxing &&
castToOuterType == expressionToOuterType)
{
if (castToOuterType.IsNullable)
{
// Even though both the nullable conversions (castToOuterType and expressionToOuterType) are equal, we can guarantee no data loss only if there is an
// implicit conversion from expression type to cast type and expression type is non-nullable. For example, consider the cast removal "(float?)" for below:
// Console.WriteLine((int)(float?)(int?)2147483647); // Prints -2147483648
// castToOuterType: ExplicitNullable
// expressionToOuterType: ExplicitNullable
// expressionToCastType: ImplicitNullable
// We should not remove the cast to "float?".
// However, cast to "int?" is unnecessary and should be removable.
return(expressionToCastType.IsImplicit && !expressionType.IsNullable());
}
else if (expressionToCastType.IsImplicit && expressionToCastType.IsNumeric && !castToOuterType.IsIdentity)
{
// Some implicit numeric conversions can cause loss of precision and must not be removed.
return(!IsRequiredImplicitNumericConversion(expressionType, castType));
}
return(true);
}
if (castToOuterType.IsIdentity &&
!expressionToCastType.IsUnboxing &&
expressionToCastType == expressionToOuterType)
{
return(true);
}
// Special case: It's possible to have useless casts inside delegate creation expressions.
// For example: new Func<string, bool>((Predicate<object>)(y => true)).
if (IsInDelegateCreationExpression(castNode, semanticModel))
{
if (expressionToCastType.IsAnonymousFunction && expressionToOuterType.IsAnonymousFunction)
{
return(!speculationAnalyzer.ReplacementChangesSemanticsOfUnchangedLambda(castedExpressionNode, speculationAnalyzer.ReplacedExpression));
}
if (expressionToCastType.IsMethodGroup && expressionToOuterType.IsMethodGroup)
{
return(true);
}
}
// Case :
// 1. IList<object> y = (IList<dynamic>)new List<object>()
if (expressionToCastType.IsExplicit && castToOuterType.IsExplicit && expressionToOuterType.IsImplicit)
{
// If both expressionToCastType and castToOuterType are numeric, then this is a required cast as one of the conversions leads to loss of precision.
// Cast removal can change program behavior.
return(!(expressionToCastType.IsNumeric && castToOuterType.IsNumeric));
}
// Case :
// 2. object y = (ValueType)1;
if (expressionToCastType.IsBoxing && expressionToOuterType.IsBoxing && castToOuterType.IsImplicit)
{
return(true);
}
// Case :
// 3. object y = (NullableValueType)null;
if ((!castToOuterType.IsBoxing || expressionToCastType.IsNullLiteral) &&
castToOuterType.IsImplicit &&
expressionToCastType.IsImplicit &&
expressionToOuterType.IsImplicit)
{
if (expressionToOuterType.IsAnonymousFunction)
{
return(expressionToCastType.IsAnonymousFunction &&
!speculationAnalyzer.ReplacementChangesSemanticsOfUnchangedLambda(castedExpressionNode, speculationAnalyzer.ReplacedExpression));
}
return(true);
}
}
return(false);
}
/// <summary>
///
/// </summary>
/// <param name="binding"></param>
/// <param name="expr"></param>
/// <param name="ept1">expr -> TypeInParent</param>
/// <param name="ept2">Type(expr) -> TypeInParent</param>
private void ConversionTestHelper(SemanticModel semanticModel, ExpressionSyntax expr, ConversionKind ept1, ConversionKind ept2)
{
var info = semanticModel.GetTypeInfo(expr);
Assert.NotNull(info);
Assert.NotNull(info.ConvertedType);
var conv = semanticModel.GetConversion(expr);
// NOT expect NoConversion
Conversion act1 = semanticModel.ClassifyConversion(expr, (TypeSymbol)info.ConvertedType);
Assert.Equal(ept1, act1.Kind);
ValidateConversion(act1, ept1);
ValidateConversion(act1, conv.Kind);
if (ept2 == ConversionKind.NoConversion)
{
Assert.Null(info.Type);
}
else
{
Assert.NotNull(info.Type);
var act2 = semanticModel.Compilation.ClassifyConversion(info.Type, info.ConvertedType);
Assert.Equal(ept2, act2.Kind);
ValidateConversion(act2, ept2);
}
}
public static bool IsUnnecessaryCast(this CastExpressionSyntax cast, SemanticModel semanticModel, CancellationToken cancellationToken)
{
var speculationAnalyzer = new SpeculationAnalyzer(cast,
cast.Expression, semanticModel, cancellationToken,
skipVerificationForReplacedNode: true, failOnOverloadResolutionFailuresInOriginalCode: true);
// First, check to see if the node ultimately parenting this cast has any
// syntax errors. If so, we bail.
if (speculationAnalyzer.SemanticRootOfOriginalExpression.ContainsDiagnostics)
{
return false;
}
var castTypeInfo = semanticModel.GetTypeInfo(cast, cancellationToken);
var castType = castTypeInfo.Type;
// Case:
// 1 . Console.WriteLine(await (dynamic)task); Any Dynamic Cast will not be removed.
if (castType == null || castType.Kind == SymbolKind.DynamicType || castType.IsErrorType())
{
return false;
}
var expressionTypeInfo = semanticModel.GetTypeInfo(cast.Expression, cancellationToken);
var expressionType = expressionTypeInfo.Type;
// We do not remove any cast on
// 1. Dynamic Expressions
// 2. If there is any other argument which is dynamic
// 3. Dynamic Invocation
if ((expressionType != null &&
(expressionType.IsErrorType() ||
expressionType.Kind == SymbolKind.DynamicType)) ||
IsDynamicInvocation(cast, semanticModel, cancellationToken))
{
return false;
}
if (PointerCastDefinitelyCantBeRemoved(cast))
{
return false;
}
if (CastPassedToParamsArrayDefinitelyCantBeRemoved(cast, castType, semanticModel, cancellationToken))
{
return false;
}
if (speculationAnalyzer.ReplacementChangesSemantics())
{
return false;
}
var expressionToCastType = semanticModel.ClassifyConversion(cast.SpanStart, cast.Expression, castType, isExplicitInSource: true);
bool parentIsOrAsExpression;
var outerType = GetOuterCastType(cast, semanticModel, out parentIsOrAsExpression) ?? castTypeInfo.ConvertedType;
// Simple case: If the conversion from the inner expression to the cast type is identity,
// the cast can be removed.
if (expressionToCastType.IsIdentity)
{
// Required explicit cast for reference comparison.
// Cast removal causes warning CS0252 (Possible unintended reference comparison).
// object x = string.Intern("Hi!");
// (object)x == "Hi!"
ExpressionSyntax other;
if (IsRequiredCastForReferenceEqualityComparison(outerType, cast, semanticModel, out other))
{
var otherToOuterType = semanticModel.ClassifyConversion(other, outerType);
if (otherToOuterType.IsImplicit && otherToOuterType.IsReference)
{
return false;
}
}
return true;
}
else if (expressionToCastType.IsExplicit && expressionToCastType.IsReference)
{
// Explicit reference conversions can cause an exception or data loss, hence can never be removed.
return false;
}
else if (expressionToCastType.IsExplicit && expressionToCastType.IsNumeric && IsInExplicitCheckedOrUncheckedContext(cast))
{
// Don't remove any explicit numeric casts in explicit checked/unchecked context.
// https://github.com/dotnet/roslyn/issues/2987 tracks improving on this conservative approach.
return false;
}
else if (expressionToCastType.IsPointer)
{
// Don't remove any non-identity pointer conversions.
// https://github.com/dotnet/roslyn/issues/2987 tracks improving on this conservative approach.
return expressionType != null && expressionType.Equals(outerType);
}
if (parentIsOrAsExpression)
{
// Note: speculationAnalyzer.ReplacementChangesSemantics() ensures that the parenting is or as expression are not broken.
// Here we just need to ensure that the original cast expression doesn't invoke a user defined operator.
return !expressionToCastType.IsUserDefined;
}
if (outerType != null)
{
var castToOuterType = semanticModel.ClassifyConversion(cast.SpanStart, cast, outerType);
var expressionToOuterType = GetSpeculatedExpressionToOuterTypeConversion(speculationAnalyzer.ReplacedExpression, speculationAnalyzer, cancellationToken);
// CONSIDER: Anonymous function conversions cannot be compared from different semantic models as lambda symbol comparison requires syntax tree equality. Should this be a compiler bug?
// For now, just revert back to computing expressionToOuterType using the original semantic model.
if (expressionToOuterType.IsAnonymousFunction)
{
expressionToOuterType = semanticModel.ClassifyConversion(cast.SpanStart, cast.Expression, outerType);
}
// If there is an user-defined conversion from the expression to the cast type or the cast
// to the outer type, we need to make sure that the same user-defined conversion will be
// called if the cast is removed.
if (castToOuterType.IsUserDefined || expressionToCastType.IsUserDefined)
{
return !expressionToOuterType.IsExplicit &&
(HaveSameUserDefinedConversion(expressionToCastType, expressionToOuterType) ||
HaveSameUserDefinedConversion(castToOuterType, expressionToOuterType)) &&
UserDefinedConversionIsAllowed(cast, semanticModel);
}
else if (expressionToOuterType.IsUserDefined)
{
return false;
}
if (expressionToCastType.IsExplicit &&
expressionToOuterType.IsExplicit)
{
return false;
}
// Required explicit cast for reference comparison.
// Cast removal causes warning CS0252 (Possible unintended reference comparison).
// object x = string.Intern("Hi!");
// x == (object)"Hi!"
ExpressionSyntax other;
if (expressionToCastType.IsImplicit && expressionToCastType.IsReference &&
castToOuterType.IsIdentity &&
IsRequiredCastForReferenceEqualityComparison(outerType, cast, semanticModel, out other))
{
return false;
}
// If the conversion from the expression to the cast type is implicit numeric or constant
// and the conversion from the expression to the outer type is identity, we'll go ahead
// and remove the cast.
if (expressionToOuterType.IsIdentity &&
expressionToCastType.IsImplicit &&
(expressionToCastType.IsNumeric || expressionToCastType.IsConstantExpression))
{
return true;
}
if (!castToOuterType.IsBoxing &&
castToOuterType == expressionToOuterType)
{
if (castToOuterType.IsNullable)
{
// Even though both the nullable conversions (castToOuterType and expressionToOuterType) are equal, we can guarantee no data loss only if there is an
// implicit conversion from expression type to cast type and expression type is non-nullable. For example, consider the cast removal "(float?)" for below:
// Console.WriteLine((int)(float?)(int?)2147483647); // Prints -2147483648
// castToOuterType: ExplicitNullable
// expressionToOuterType: ExplicitNullable
// expressionToCastType: ImplicitNullable
// We should not remove the cast to "float?".
// However, cast to "int?" is unnecessary and should be removable.
return expressionToCastType.IsImplicit && !((ITypeSymbol)expressionType).IsNullable();
}
else if (expressionToCastType.IsImplicit && expressionToCastType.IsNumeric && !castToOuterType.IsIdentity)
{
// Some implicit numeric conversions can cause loss of precision and must not be removed.
return !IsRequiredImplicitNumericConversion(expressionType, castType);
}
return true;
}
if (castToOuterType.IsIdentity &&
!expressionToCastType.IsUnboxing &&
expressionToCastType == expressionToOuterType)
{
return true;
}
// Special case: It's possible to have useless casts inside delegate creation expressions.
// For example: new Func<string, bool>((Predicate<object>)(y => true)).
if (IsInDelegateCreationExpression(cast, semanticModel))
{
if (expressionToCastType.IsAnonymousFunction && expressionToOuterType.IsAnonymousFunction)
{
return !speculationAnalyzer.ReplacementChangesSemanticsOfUnchangedLambda(cast.Expression, speculationAnalyzer.ReplacedExpression);
}
if (expressionToCastType.IsMethodGroup && expressionToOuterType.IsMethodGroup)
{
return true;
}
}
// Case :
// 1. IList<object> y = (IList<dynamic>)new List<object>()
if (expressionToCastType.IsExplicit && castToOuterType.IsExplicit && expressionToOuterType.IsImplicit)
{
// If both expressionToCastType and castToOuterType are numeric, then this is a required cast as one of the conversions leads to loss of precision.
// Cast removal can change program behavior.
return !(expressionToCastType.IsNumeric && castToOuterType.IsNumeric);
}
// Case :
// 2. object y = (ValueType)1;
if (expressionToCastType.IsBoxing && expressionToOuterType.IsBoxing && castToOuterType.IsImplicit)
{
return true;
}
// Case :
// 3. object y = (NullableValueType)null;
if ((!castToOuterType.IsBoxing || expressionToCastType.IsNullLiteral) &&
castToOuterType.IsImplicit &&
expressionToCastType.IsImplicit &&
expressionToOuterType.IsImplicit)
{
if (expressionToOuterType.IsAnonymousFunction)
{
return expressionToCastType.IsAnonymousFunction &&
!speculationAnalyzer.ReplacementChangesSemanticsOfUnchangedLambda(cast.Expression, speculationAnalyzer.ReplacedExpression);
}
return true;
}
}
return false;
}
