static void addFromClassOrStruct(ArrayBuilder <TypeSymbol> result, bool excludeExisting, TypeSymbol type, bool includeBaseTypes, ref CompoundUseSiteInfo <AssemblySymbol> useSiteInfo)
{
if (type.IsClassType() || type.IsStructType())
{
if (!excludeExisting || !HasIdentityConversionToAny(type, result))
{
result.Add(type);
}
}
if (!includeBaseTypes)
{
return;
}
NamedTypeSymbol t = type.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteInfo);
while ((object)t != null)
{
if (!excludeExisting || !HasIdentityConversionToAny(t, result))
{
result.Add(t);
}
t = t.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteInfo);
}
}
public static void AddTypesParticipatingInUserDefinedConversion(
ArrayBuilder <NamedTypeSymbol> result,
TypeSymbol type,
bool includeBaseTypes,
ref CompoundUseSiteInfo <AssemblySymbol> useSiteInfo
)
{
if ((object)type == null)
{
return;
}
// CONSIDER: These sets are usually small; if they are large then this is an O(n^2)
// CONSIDER: algorithm. We could use a hash table instead to build up the set.
Debug.Assert(!type.IsTypeParameter());
// optimization:
bool excludeExisting = result.Count > 0;
if (type.IsClassType() || type.IsStructType())
{
var namedType = (NamedTypeSymbol)type;
if (!excludeExisting || !HasIdentityConversionToAny(namedType, result))
{
result.Add(namedType);
}
}
if (!includeBaseTypes)
{
return;
}
NamedTypeSymbol t = type.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteInfo);
while ((object)t != null)
{
if (!excludeExisting || !HasIdentityConversionToAny(t, result))
{
result.Add(t);
}
t = t.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteInfo);
}
}
public static void AddTypesParticipatingInUserDefinedConversion(ArrayBuilder <NamedTypeSymbol> result, TypeSymbol type, bool includeBaseTypes, ref HashSet <DiagnosticInfo> useSiteDiagnostics)
{
if ((object)type == null)
{
return;
}
// CONSIDER: These sets are usually small; if they are large then this is an O(n^2)
// CONSIDER: algorithm. We could use a hash table instead to build up the set.
Debug.Assert(!type.IsTypeParameter());
// optimization:
bool excludeExisting = result.Count > 0;
// The decimal type does not contribute its user-defined conversions to the mix; though its
// conversions are actually implemented via user-defined operators, we logically treat it as
// though those conversions were built-in.
if (type.IsClassType() || type.IsStructType() && type.SpecialType != SpecialType.System_Decimal)
{
var namedType = (NamedTypeSymbol)type;
if (!excludeExisting || !HasIdentityConversionToAny(namedType, result))
{
result.Add(namedType);
}
}
if (!includeBaseTypes)
{
return;
}
NamedTypeSymbol t = type.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteDiagnostics);
while ((object)t != null)
{
if (!excludeExisting || !HasIdentityConversionToAny(t, result))
{
result.Add(t);
}
t = t.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteDiagnostics);
}
}
public static void AddTypesParticipatingInUserDefinedConversion(ArrayBuilder<NamedTypeSymbol> result, TypeSymbol type, bool includeBaseTypes, ref HashSet<DiagnosticInfo> useSiteDiagnostics)
{
if ((object)type == null)
{
return;
}
// CONSIDER: These sets are usually small; if they are large then this is an O(n^2)
// CONSIDER: algorithm. We could use a hash table instead to build up the set.
Debug.Assert(!type.IsTypeParameter());
// optimization:
bool excludeExisting = result.Count > 0;
// The decimal type does not contribute its user-defined conversions to the mix; though its
// conversions are actually implemented via user-defined operators, we logically treat it as
// though those conversions were built-in.
if (type.IsClassType() || type.IsStructType() && type.SpecialType != SpecialType.System_Decimal)
{
var namedType = (NamedTypeSymbol)type;
if (!excludeExisting || !HasIdentityConversionToAny(namedType, result))
{
result.Add(namedType);
}
}
if (!includeBaseTypes)
{
return;
}
NamedTypeSymbol t = type.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteDiagnostics);
while ((object)t != null)
{
if (!excludeExisting || !HasIdentityConversionToAny(t, result))
{
result.Add(t);
}
t = t.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteDiagnostics);
}
}
public static void AddTypesParticipatingInUserDefinedConversion(ArrayBuilder<NamedTypeSymbol> result, TypeSymbol type, bool includeBaseTypes, ref HashSet<DiagnosticInfo> useSiteDiagnostics)
{
if ((object)type == null)
{
return;
}
// CONSIDER: These sets are usually small; if they are large then this is an O(n^2)
// CONSIDER: algorithm. We could use a hash table instead to build up the set.
Debug.Assert(!type.IsTypeParameter());
// optimization:
bool excludeExisting = result.Count > 0;
if (type.IsClassType() || type.IsStructType())
{
var namedType = (NamedTypeSymbol)type;
if (!excludeExisting || !HasIdentityConversionToAny(namedType, result))
{
result.Add(namedType);
}
}
if (!includeBaseTypes)
{
return;
}
NamedTypeSymbol t = type.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteDiagnostics);
while ((object)t != null)
{
if (!excludeExisting || !HasIdentityConversionToAny(t, result))
{
result.Add(t);
}
t = t.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteDiagnostics);
}
}
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);
}
}
internal static ConstantValue GetAsOperatorConstantResult(TypeSymbol operandType, TypeSymbol targetType, ConversionKind conversionKind, ConstantValue operandConstantValue)
{
// 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.
// Native compiler port:
// // check for case we know is always false
// if (arg->isNull() || !canCast(arg, type2, NOUDC) && type1->IsValType() && type2->isClassType() && (!type1->IsTypeParameterType() || !type2->isPredefType(PT_ENUM)))
// {
// GetErrorContext()->Error(tree, WRN_AlwaysNull, type2);
// return rval;
// }
if (operandConstantValue == ConstantValue.Null ||
(conversionKind == ConversionKind.NoConversion &&
(operandType.IsValueType && targetType.IsClassType() && (!operandType.IsTypeParameter() || targetType.SpecialType != SpecialType.System_Enum))))
{
return ConstantValue.Null;
}
else
{
return null;
}
}
