private static bool ReportAsOperatorConversionDiagnostics(
CSharpSyntaxNode node,
DiagnosticBag diagnostics,
Compilation compilation,
TypeSymbol operandType,
TypeSymbol targetType,
ConversionKind conversionKind,
ConstantValue operandConstantValue)
{
// SPEC: In an operation of the form E as T, E must be an expression and T must be a reference type,
// SPEC: a type parameter known to be a reference type, or a nullable type.
// SPEC: Furthermore, at least one of the following must be true, or otherwise a compile-time error occurs:
// SPEC: • An identity (§6.1.1), implicit nullable (§6.1.4), implicit reference (§6.1.6), boxing (§6.1.7),
// SPEC: explicit nullable (§6.2.3), explicit reference (§6.2.4), or unboxing (§6.2.5) conversion exists
// SPEC: from E to T.
// SPEC: • The type of E or T is an open type.
// SPEC: • E is the null literal.
// SPEC VIOLATION: The specification contains an error in the list of legal conversions above.
// SPEC VIOLATION: If we have "class C<T, U> where T : U where U : class" then there is
// SPEC VIOLATION: an implicit conversion from T to U, but it is not an identity, reference or
// SPEC VIOLATION: boxing conversion. It will be one of those at runtime, but at compile time
// SPEC VIOLATION: we do not know which, and therefore cannot classify it as any of those.
// SPEC VIOLATION: See Microsoft.CodeAnalysis.CSharp.UnitTests.SyntaxBinderTests.TestAsOperator_SpecErrorCase() test for an example.
// SPEC VIOLATION: The specification also unintentionally allows the case where requirement 2 above:
// SPEC VIOLATION: "The type of E or T is an open type" is true, but type of E is void type, i.e. T is an open type.
// SPEC VIOLATION: Dev10 compiler correctly generates an error for this case and we will maintain compatibility.
bool hasErrors = false;
switch (conversionKind)
{
case ConversionKind.ImplicitReference:
case ConversionKind.Boxing:
case ConversionKind.ImplicitNullable:
case ConversionKind.Identity:
case ConversionKind.ExplicitNullable:
case ConversionKind.ExplicitReference:
case ConversionKind.Unboxing:
break;
default:
// Generate an error if there is no possible legal conversion and both the operandType
// and the targetType are closed types OR operandType is void type, otherwise we need a runtime check
if (!operandType.ContainsTypeParameter() && !targetType.ContainsTypeParameter() ||
operandType.SpecialType == SpecialType.System_Void)
{
SymbolDistinguisher distinguisher = new SymbolDistinguisher(compilation, operandType, targetType);
Error(diagnostics, ErrorCode.ERR_NoExplicitBuiltinConv, node, distinguisher.First, distinguisher.Second);
hasErrors = true;
}
break;
}
if (!hasErrors)
{
ReportAsOperatorConstantWarnings(node, diagnostics, operandType, targetType, conversionKind, operandConstantValue);
}
return hasErrors;
}
internal static ConstantValue GetIsOperatorConstantResult(TypeSymbol operandType, TypeSymbol targetType, ConversionKind conversionKind, ConstantValue operandConstantValue)
{
Debug.Assert((object)targetType != null);
// SPEC: The result of the operation depends on D and T as follows:
// SPEC: 1) If T is a reference type, the result is true if D and T are the same type, if D is a reference type and
// SPEC: an implicit reference conversion from D to T exists, or if D is a value type and a boxing conversion from D to T exists.
// SPEC: 2) If T is a nullable type, the result is true if D is the underlying type of T.
// SPEC: 3) If T is a non-nullable value type, the result is true if D and T are the same type.
// SPEC: 4) Otherwise, the result is false.
// NOTE: The language specification talks about the runtime evaluation of the is operation.
// NOTE: However, we are interested in computing the compile time constant value for the expression.
// NOTE: Even though BoundIsOperator and BoundAsOperator will always have no ConstantValue
// NOTE: (they are non-constant expressions according to Section 7.19 of the specification),
// NOTE: we want to perform constant analysis of is/as expressions during binding to generate warnings (always true/false/null)
// NOTE: and during rewriting for optimized codegen.
// NOTE:
// NOTE: Because the heuristic presented here is used to change codegen, it must be conservative. It is acceptable
// NOTE: for us to fail to report a warning in cases where humans could logically deduce that the operator will
// NOTE: always return false. It is not acceptable to inaccurately warn that the operator will always return false
// NOTE: if there are cases where it might succeed.
//
// To begin our heuristic: if the operand is literal null then we automatically return that the
// result is false. You might think that we can simply check to see if the conversion is
// ConversionKind.NullConversion, but "null is T" for a type parameter T is actually classified
// as an implicit reference conversion if T is constrained to reference types. Rather
// than deal with all those special cases we can simply bail out here.
if (operandConstantValue == ConstantValue.Null)
{
return ConstantValue.False;
}
Debug.Assert((object)operandType != null);
switch (conversionKind)
{
case ConversionKind.NoConversion:
// Oddly enough, "x is T" can be true even if there is no conversion from x to T!
//
// Scenario 1: Type parameter compared to System.Enum.
//
// bool M1<X>(X x) where X : struct { return x is Enum; }
//
// There is no conversion from X to Enum, not even an explicit conversion. But
// nevertheless, X could be constructed as an enumerated type.
// However, we can sometimes know that the result will be false.
//
// Scenario 2: Constrained type parameter compared to reference type.
//
// bool M2<X>(X x) where X : struct { return x is string; }
//
// We know that X, constrained to struct, will never be string.
//
// Scenario 3: Value type compared to type parameter.
//
// bool M3<T>(int x) { return x is T; }
//
// There is no conversion from int to T, but T could nevertheless be int.
//
// Scenario 4: Constructed type compared to open type
//
// bool M4<T>(C<int> x) { return x is C<T>; }
//
// There is no conversion from C<int> to C<T>, but nevertheless, T might be int.
//
// Scenario 5: Open type compared to constructed type:
//
// bool M5<X>(C<X> x) { return x is C<int>);
//
// Again, X could be int.
//
// We could then go on to get more complicated. For example,
//
// bool M6<X>(C<X> x) where X : struct { return x is C<string>; }
//
// We know that C<X> is never convertible to C<string> no matter what
// X is. Or:
//
// bool M7<T>(Dictionary<int, int> x) { return x is List<T>; }
//
// We know that no matter what T is, the conversion will never succeed.
//
// As noted above, we must be conservative. We follow the lead of the native compiler,
// which uses the following algorithm:
//
// * If neither type is open and there is no conversion then the result is always false:
if (!operandType.ContainsTypeParameter() && !targetType.ContainsTypeParameter())
{
return ConstantValue.False;
}
// * Otherwise, at least one of them is of an open type. If the operand is of value type
// and the target is a class type other than System.Enum, then we are in scenario 2,
// not scenario 1, and can correctly deduce that the result is false.
if (operandType.IsValueType && targetType.IsClassType() && targetType.SpecialType != SpecialType.System_Enum)
{
return ConstantValue.False;
}
// * Otherwise, we give up. Though there are other situations in which we can deduce that
// the result will always be false, such as scenarios 6 and 7, but we do not attempt
// to deduce this.
// CONSIDER: we could use TypeUnification.CanUnify to do additional compile-time checking.
return null;
case ConversionKind.ImplicitNumeric:
case ConversionKind.ExplicitNumeric:
case ConversionKind.ImplicitEnumeration:
// case ConversionKind.ExplicitEnumeration: // Handled separately below.
case ConversionKind.ImplicitConstant:
case ConversionKind.ImplicitUserDefined:
case ConversionKind.ExplicitUserDefined:
case ConversionKind.IntPtr:
// Consider all the cases where we know that "x is T" must be false just from
// the conversion classification.
//
// If we have "x is T" and the conversion from x to T is numeric or enum then the result must be false.
//
// If we have "null is T" then obviously that must be false.
//
// If we have "1 is long" then that must be false. (If we have "1 is int" then it is an identity conversion,
// not an implicit constant conversion.
//
// User-defined and IntPtr conversions are always false for "is".
return ConstantValue.False;
case ConversionKind.ExplicitEnumeration:
// Enum-to-enum conversions should be treated the same as unsuccessful struct-to-struct
// conversions (i.e. make allowances for type unification, etc)
if (operandType.IsEnumType() && targetType.IsEnumType())
{
goto case ConversionKind.NoConversion;
}
return ConstantValue.False;
case ConversionKind.ExplicitNullable:
// An explicit nullable conversion is a conversion of one of the following forms:
//
// 1) X? --> Y?, where X --> Y is an explicit conversion. (If X --> Y is an implicit
// conversion then X? --> Y? is an implicit nullable conversion.) In this case we
// know that "X? is Y?" must be false because either X? is null, or we have an
// explicit conversion from struct type X to struct type Y, and so X is never of type Y.)
//
// 2) X --> Y?, where again, X --> Y is an explicit conversion. By the same reasoning
// as in case 1, this must be false.
if (targetType.IsNullableType())
{
return ConstantValue.False;
}
Debug.Assert(operandType.IsNullableType());
// 3) X? --> X. In this case, this is just a different way of writing "x != null".
// We do not know what the result will be.
// CONSIDER: If we know statically that the operand is going to be null or non-null
// CONSIDER: then we could give a better result here.
if (Conversions.HasIdentityConversion(operandType.GetNullableUnderlyingType(), targetType))
{
return null;
}
// 4) X? --> Y where the conversion X --> Y is an implicit or explicit value type conversion.
// "X? is Y" again must be false.
return ConstantValue.False;
case ConversionKind.ImplicitReference:
case ConversionKind.ExplicitReference:
case ConversionKind.Unboxing:
// In these three cases, the expression type must be a reference type. Therefore,
// the result cannot be determined. The expression could be null, resulting
// in false, or it could be a non-null reference to the appropriate type,
// resulting in true.
return null;
case ConversionKind.Identity:
// The result of "x is T" can be statically determined to be true if x is an expression
// of non-nullable value type T. If x is of reference or nullable value type then
// we cannot know, because again, the expression value could be null or it could be good.
// If it is of pointer type then we have already given an error.
return (operandType.IsValueType && !operandType.IsNullableType()) ? ConstantValue.True : null;
case ConversionKind.Boxing:
// A boxing conversion might be a conversion:
//
// * From a non-nullable value type to a reference type
// * From a nullable value type to a reference type
// * From a type parameter that *could* be a value type under construction
// to a reference type
//
// In the first case we know that the conversion will always succeed and that the
// operand is never null, and therefore "is" will always result in true.
//
// In the second two cases we do not know; either the nullable value type could be
// null, or the type parameter could be constructed with a reference type, and it
// could be null.
return operandType.IsValueType && !operandType.IsNullableType() ? ConstantValue.True : null;
case ConversionKind.ImplicitNullable:
// We have "x is T" in one of the following situations:
// 1) x is of type X and T is X?. The value is always true.
// 2) x is of type X and T is Y? where X is convertible to Y via an implicit numeric conversion. Eg,
// x is of type int and T is decimal?. The value is always false.
// 3) x is of type X? and T is Y? where X is convertible to Y via an implicit numeric conversion.
// The value is always false.
Debug.Assert(targetType.IsNullableType());
return (operandType == targetType.GetNullableUnderlyingType()) ? ConstantValue.True : ConstantValue.False;
default:
case ConversionKind.ImplicitDynamic:
case ConversionKind.ExplicitDynamic:
case ConversionKind.PointerToInteger:
case ConversionKind.PointerToPointer:
case ConversionKind.PointerToVoid:
case ConversionKind.IntegerToPointer:
case ConversionKind.NullToPointer:
case ConversionKind.AnonymousFunction:
case ConversionKind.NullLiteral:
case ConversionKind.MethodGroup:
// We've either replaced Dynamic with Object, or already bailed out with an error.
throw ExceptionUtilities.UnexpectedValue(conversionKind);
}
}
/// <summary>
/// Return the side-effect expression corresponding to an evaluation.
/// </summary>
protected BoundExpression LowerEvaluation(BoundDagEvaluation evaluation)
{
BoundExpression input = _tempAllocator.GetTemp(evaluation.Input);
switch (evaluation)
{
case BoundDagFieldEvaluation f:
{
FieldSymbol field = f.Field;
var outputTemp = new BoundDagTemp(f.Syntax, field.Type.TypeSymbol, f, index: 0);
BoundExpression output = _tempAllocator.GetTemp(outputTemp);
BoundExpression access = _localRewriter.MakeFieldAccess(f.Syntax, input, field, null, LookupResultKind.Viable, field.Type.TypeSymbol);
access.WasCompilerGenerated = true;
return(_factory.AssignmentExpression(output, access));
}
case BoundDagPropertyEvaluation p:
{
PropertySymbol property = p.Property;
var outputTemp = new BoundDagTemp(p.Syntax, property.Type.TypeSymbol, p, index: 0);
BoundExpression output = _tempAllocator.GetTemp(outputTemp);
return(_factory.AssignmentExpression(output, _factory.Property(input, property)));
}
case BoundDagDeconstructEvaluation d:
{
MethodSymbol method = d.DeconstructMethod;
var refKindBuilder = ArrayBuilder <RefKind> .GetInstance();
var argBuilder = ArrayBuilder <BoundExpression> .GetInstance();
BoundExpression receiver;
void addArg(RefKind refKind, BoundExpression expression)
{
refKindBuilder.Add(refKind);
argBuilder.Add(expression);
}
Debug.Assert(method.Name == WellKnownMemberNames.DeconstructMethodName);
int extensionExtra;
if (method.IsStatic)
{
Debug.Assert(method.IsExtensionMethod);
receiver = _factory.Type(method.ContainingType);
addArg(method.ParameterRefKinds[0], input);
extensionExtra = 1;
}
else
{
receiver = input;
extensionExtra = 0;
}
for (int i = extensionExtra; i < method.ParameterCount; i++)
{
ParameterSymbol parameter = method.Parameters[i];
Debug.Assert(parameter.RefKind == RefKind.Out);
var outputTemp = new BoundDagTemp(d.Syntax, parameter.Type.TypeSymbol, d, i - extensionExtra);
addArg(RefKind.Out, _tempAllocator.GetTemp(outputTemp));
}
return(_factory.Call(receiver, method, refKindBuilder.ToImmutableAndFree(), argBuilder.ToImmutableAndFree()));
}
case BoundDagTypeEvaluation t:
{
TypeSymbol inputType = input.Type;
if (inputType.IsDynamic() || inputType.ContainsTypeParameter())
{
inputType = _factory.SpecialType(SpecialType.System_Object);
}
TypeSymbol type = t.Type;
var outputTemp = new BoundDagTemp(t.Syntax, type, t, index: 0);
BoundExpression output = _tempAllocator.GetTemp(outputTemp);
HashSet <DiagnosticInfo> useSiteDiagnostics = null;
Conversion conversion = _factory.Compilation.Conversions.ClassifyBuiltInConversion(inputType, output.Type, ref useSiteDiagnostics);
_localRewriter._diagnostics.Add(t.Syntax, useSiteDiagnostics);
BoundExpression evaluated;
if (conversion.Exists)
{
if (conversion.Kind == ConversionKind.ExplicitNullable &&
inputType.GetNullableUnderlyingType().Equals(output.Type, TypeCompareKind.AllIgnoreOptions) &&
_localRewriter.TryGetNullableMethod(t.Syntax, inputType, SpecialMember.System_Nullable_T_GetValueOrDefault, out MethodSymbol getValueOrDefault))
{
// As a special case, since the null test has already been done we can use Nullable<T>.GetValueOrDefault
evaluated = _factory.Call(input, getValueOrDefault);
}
else
{
evaluated = _factory.Convert(type, input, conversion);
}
}
else
{
evaluated = _factory.As(input, type);
}
return(_factory.AssignmentExpression(output, evaluated));
}
case BoundDagIndexEvaluation e:
{
// This is an evaluation of an indexed property with a constant int value.
// The input type must be ITuple, and the property must be a property of ITuple.
Debug.Assert(e.Property.ContainingSymbol.Equals(input.Type));
Debug.Assert(e.Property.GetMethod.ParameterCount == 1);
Debug.Assert(e.Property.GetMethod.Parameters[0].Type.SpecialType == SpecialType.System_Int32);
TypeSymbol type = e.Property.GetMethod.ReturnType.TypeSymbol;
var outputTemp = new BoundDagTemp(e.Syntax, type, e, index: 0);
BoundExpression output = _tempAllocator.GetTemp(outputTemp);
return(_factory.AssignmentExpression(output, _factory.Call(input, e.Property.GetMethod, _factory.Literal(e.Index))));
}
default:
throw ExceptionUtilities.UnexpectedValue(evaluation);
}
}
/// <summary>
/// Check that the pattern type is valid for the operand. Return true if an error was reported.
/// </summary>
private bool CheckValidPatternType(
CSharpSyntaxNode typeSyntax,
TypeSymbol operandType,
TypeSymbol patternType,
bool patternTypeWasInSource,
bool isVar,
DiagnosticBag diagnostics)
{
Debug.Assert((object)operandType != null);
Debug.Assert((object)patternType != null);
if (operandType.IsErrorType() || patternType.IsErrorType())
{
return(false);
}
else if (patternType.IsNullableType() && !isVar && patternTypeWasInSource)
{
// It is an error to use pattern-matching with a nullable type, because you'll never get null. Use the underlying type.
Error(diagnostics, ErrorCode.ERR_PatternNullableType, typeSyntax, patternType, patternType.GetNullableUnderlyingType());
return(true);
}
else if (patternType.IsStatic)
{
Error(diagnostics, ErrorCode.ERR_VarDeclIsStaticClass, typeSyntax, patternType);
return(true);
}
else if (!isVar)
{
if (patternType.IsDynamic())
{
Error(diagnostics, ErrorCode.ERR_PatternDynamicType, typeSyntax);
return(true);
}
HashSet <DiagnosticInfo> useSiteDiagnostics = null;
var matchPossible = ExpressionOfTypeMatchesPatternType(Conversions, operandType, patternType, ref useSiteDiagnostics, out Conversion conversion, operandConstantValue: null, operandCouldBeNull: true);
diagnostics.Add(typeSyntax, useSiteDiagnostics);
if (matchPossible != false)
{
if (!conversion.Exists && (operandType.ContainsTypeParameter() || patternType.ContainsTypeParameter()))
{
// permit pattern-matching when one of the types is an open type in C# 7.1.
LanguageVersion requiredVersion = MessageID.IDS_FeatureGenericPatternMatching.RequiredVersion();
if (requiredVersion > Compilation.LanguageVersion)
{
Error(diagnostics, ErrorCode.ERR_PatternWrongGenericTypeInVersion, typeSyntax,
operandType, patternType,
Compilation.LanguageVersion.ToDisplayString(),
new CSharpRequiredLanguageVersion(requiredVersion));
return(true);
}
}
}
else
{
Error(diagnostics, ErrorCode.ERR_PatternWrongType, typeSyntax, operandType, patternType);
return(true);
}
}
return(false);
}
/// <summary>
/// Check that the pattern type is valid for the operand. Return true if an error was reported.
/// </summary>
private bool CheckValidPatternType(
CSharpSyntaxNode typeSyntax,
BoundExpression operand,
TypeSymbol operandType,
TypeSymbol patternType,
bool patternTypeWasInSource,
bool isVar,
DiagnosticBag diagnostics)
{
Debug.Assert((object)operandType != null);
Debug.Assert((object)patternType != null);
// Because we do not support recursive patterns, we always have an operand
Debug.Assert((object)operand != null);
// Once we support recursive patterns that will be relaxed.
if (operandType.IsErrorType() || patternType.IsErrorType())
{
return(false);
}
else if (patternType.IsNullableType() && !isVar && patternTypeWasInSource)
{
// It is an error to use pattern-matching with a nullable type, because you'll never get null. Use the underlying type.
Error(diagnostics, ErrorCode.ERR_PatternNullableType, typeSyntax, patternType, patternType.GetNullableUnderlyingType());
return(true);
}
else if (patternType.IsStatic)
{
Error(diagnostics, ErrorCode.ERR_VarDeclIsStaticClass, typeSyntax, patternType);
return(true);
}
else if (!isVar)
{
if (patternType.IsDynamic())
{
Error(diagnostics, ErrorCode.ERR_PatternDynamicType, typeSyntax);
return(true);
}
HashSet <DiagnosticInfo> useSiteDiagnostics = null;
Conversion conversion =
operand != null
? this.Conversions.ClassifyConversionFromExpression(operand, patternType, ref useSiteDiagnostics, forCast : true)
: this.Conversions.ClassifyConversionFromType(operandType, patternType, ref useSiteDiagnostics, forCast: true);
diagnostics.Add(typeSyntax, useSiteDiagnostics);
switch (conversion.Kind)
{
case ConversionKind.ExplicitDynamic:
case ConversionKind.ImplicitDynamic:
// Since the input was `dynamic`, which is equivalent to `object`, there must also
// exist some unboxing, identity, or reference conversion as well, making the conversion legal.
case ConversionKind.Boxing:
case ConversionKind.ExplicitNullable:
case ConversionKind.ExplicitReference:
case ConversionKind.Identity:
case ConversionKind.ImplicitReference:
case ConversionKind.Unboxing:
case ConversionKind.ImplicitNullable:
// these are the conversions allowed by a pattern match
break;
case ConversionKind.DefaultOrNullLiteral:
throw ExceptionUtilities.UnexpectedValue(conversion.Kind);
//case ConversionKind.ExplicitNumeric: // we do not perform numeric conversions of the operand
//case ConversionKind.ImplicitConstant:
//case ConversionKind.ImplicitNumeric:
default:
if (operandType.ContainsTypeParameter() || patternType.ContainsTypeParameter())
{
LanguageVersion requiredVersion = MessageID.IDS_FeatureGenericPatternMatching.RequiredVersion();
if (requiredVersion > Compilation.LanguageVersion)
{
Error(diagnostics, ErrorCode.ERR_PatternWrongGenericTypeInVersion, typeSyntax,
operandType, patternType,
Compilation.LanguageVersion.ToDisplayString(),
new CSharpRequiredLanguageVersion(requiredVersion));
return(true);
}
// permit pattern-matching when one of the types is an open type in C# 7.1.
break;
}
else
{
Error(diagnostics, ErrorCode.ERR_PatternWrongType, typeSyntax, operandType, patternType);
return(true);
}
}
}
return(false);
}
