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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
#nullable disable
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Diagnostics;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.PooledObjects;
using Roslyn.Utilities;
namespace Microsoft.CodeAnalysis.CSharp
{
internal sealed partial class OverloadResolution
{
private NamedTypeSymbol MakeNullable(TypeSymbol type)
{
return Compilation.GetSpecialType(SpecialType.System_Nullable_T).Construct(type);
}
public void UnaryOperatorOverloadResolution(UnaryOperatorKind kind, bool isChecked, BoundExpression operand, UnaryOperatorOverloadResolutionResult result, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
Debug.Assert(operand != null);
Debug.Assert(result.Results.Count == 0);
// We can do a table lookup for well-known problems in overload resolution.
UnaryOperatorEasyOut(kind, operand, result);
if (result.Results.Count > 0)
{
return;
}
// SPEC: An operation of the form op x or x op, where op is an overloadable unary operator,
// SPEC: and x is an expression of type X, is processed as follows:
// SPEC: The set of candidate user-defined operators provided by X for the operation operator
// SPEC: op(x) is determined using the rules of 7.3.5.
bool hadUserDefinedCandidate = GetUserDefinedOperators(kind, isChecked, operand, result.Results, ref useSiteInfo);
// SPEC: If the set of candidate user-defined operators is not empty, then this becomes the
// SPEC: set of candidate operators for the operation. Otherwise, the predefined unary operator
// SPEC: implementations, including their lifted forms, become the set of candidate operators
// SPEC: for the operation.
if (!hadUserDefinedCandidate)
{
result.Results.Clear();
GetAllBuiltInOperators(kind, isChecked, operand, result.Results, ref useSiteInfo);
}
// SPEC: The overload resolution rules of 7.5.3 are applied to the set of candidate operators
// SPEC: to select the best operator with respect to the argument list (x), and this operator
// SPEC: becomes the result of the overload resolution process. If overload resolution fails
// SPEC: to select a single best operator, a binding-time error occurs.
UnaryOperatorOverloadResolution(operand, result, ref useSiteInfo);
}
// Takes a list of candidates and mutates the list to throw out the ones that are worse than
// another applicable candidate.
private void UnaryOperatorOverloadResolution(
BoundExpression operand,
UnaryOperatorOverloadResolutionResult result,
ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
// SPEC: Given the set of applicable candidate function members, the best function member in that set is located.
// SPEC: If the set contains only one function member, then that function member is the best function member.
if (result.SingleValid())
{
return;
}
var candidates = result.Results;
RemoveLowerPriorityMembers<UnaryOperatorAnalysisResult, MethodSymbol>(candidates);
// SPEC: Otherwise, the best function member is the one function member that is better than all other function
// SPEC: members with respect to the given argument list, provided that each function member is compared to all
// SPEC: other function members using the rules in 7.5.3.2. If there is not exactly one function member that is
// SPEC: better than all other function members, then the function member invocation is ambiguous and a binding-time
// SPEC: error occurs.
// Try to find a single best candidate
int bestIndex = GetTheBestCandidateIndex(operand, candidates, ref useSiteInfo);
if (bestIndex != -1)
{
// Mark all other candidates as worse
for (int index = 0; index < candidates.Count; ++index)
{
if (candidates[index].Kind != OperatorAnalysisResultKind.Inapplicable && index != bestIndex)
{
candidates[index] = candidates[index].Worse();
}
}
return;
}
for (int i = 1; i < candidates.Count; ++i)
{
if (candidates[i].Kind != OperatorAnalysisResultKind.Applicable)
{
continue;
}
// Is this applicable operator better than every other applicable method?
for (int j = 0; j < i; ++j)
{
if (candidates[j].Kind == OperatorAnalysisResultKind.Inapplicable)
{
continue;
}
var better = BetterOperator(candidates[i].Signature, candidates[j].Signature, operand, ref useSiteInfo);
if (better == BetterResult.Left)
{
candidates[j] = candidates[j].Worse();
}
else if (better == BetterResult.Right)
{
candidates[i] = candidates[i].Worse();
}
}
}
}
private int GetTheBestCandidateIndex(
BoundExpression operand,
ArrayBuilder<UnaryOperatorAnalysisResult> candidates,
ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
int currentBestIndex = -1;
for (int index = 0; index < candidates.Count; index++)
{
if (candidates[index].Kind != OperatorAnalysisResultKind.Applicable)
{
continue;
}
// Assume that the current candidate is the best if we don't have any
if (currentBestIndex == -1)
{
currentBestIndex = index;
}
else
{
var better = BetterOperator(candidates[currentBestIndex].Signature, candidates[index].Signature, operand, ref useSiteInfo);
if (better == BetterResult.Right)
{
// The current best is worse
currentBestIndex = index;
}
else if (better != BetterResult.Left)
{
// The current best is not better
currentBestIndex = -1;
}
}
}
// Make sure that every candidate up to the current best is worse
for (int index = 0; index < currentBestIndex; index++)
{
if (candidates[index].Kind == OperatorAnalysisResultKind.Inapplicable)
{
continue;
}
var better = BetterOperator(candidates[currentBestIndex].Signature, candidates[index].Signature, operand, ref useSiteInfo);
if (better != BetterResult.Left)
{
// The current best is not better
return -1;
}
}
return currentBestIndex;
}
private BetterResult BetterOperator(UnaryOperatorSignature op1, UnaryOperatorSignature op2, BoundExpression operand, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
// First we see if the conversion from the operand to one operand type is better than
// the conversion to the other.
BetterResult better = BetterConversionFromExpression(operand, op1.OperandType, op2.OperandType, ref useSiteInfo);
if (better == BetterResult.Left || better == BetterResult.Right)
{
return better;
}
// There was no better member on the basis of conversions. Go to the tiebreaking round.
// SPEC: In case the parameter type sequences P1, P2 and Q1, Q2 are equivalent -- that is, every Pi
// SPEC: has an identity conversion to the corresponding Qi -- the following tie-breaking rules
// SPEC: are applied:
if (Conversions.HasIdentityConversion(op1.OperandType, op2.OperandType))
{
// SPEC: If Mp has more specific parameter types than Mq then Mp is better than Mq.
// Under what circumstances can two unary operators with identical signatures be "more specific"
// than another? With a binary operator you could have C<T>.op+(C<T>, T) and C<T>.op+(C<T>, int).
// When doing overload resolution on C<int> + int, the latter is more specific. But with a unary
// operator, the sole operand *must* be the containing type or its nullable type. Therefore
// if there is an identity conversion, then the parameters really were identical. We therefore
// skip checking for specificity.
// SPEC: If one member is a non-lifted operator and the other is a lifted operator,
// SPEC: the non-lifted one is better.
bool lifted1 = op1.Kind.IsLifted();
bool lifted2 = op2.Kind.IsLifted();
if (lifted1 && !lifted2)
{
return BetterResult.Right;
}
else if (!lifted1 && lifted2)
{
return BetterResult.Left;
}
}
// Always prefer operators with val parameters over operators with in parameters:
if (op1.RefKind == RefKind.None && op2.RefKind == RefKind.In)
{
return BetterResult.Left;
}
else if (op2.RefKind == RefKind.None && op1.RefKind == RefKind.In)
{
return BetterResult.Right;
}
return BetterResult.Neither;
}
private void GetAllBuiltInOperators(UnaryOperatorKind kind, bool isChecked, BoundExpression operand, ArrayBuilder<UnaryOperatorAnalysisResult> results, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
// The spec states that overload resolution is performed upon the infinite set of
// operators defined on enumerated types, pointers and delegates. Clearly we cannot
// construct the infinite set; we have to pare it down. Previous implementations of C#
// implement a much stricter rule; they only add the special operators to the candidate
// set if one of the operands is of the relevant type. This means that operands
// involving user-defined implicit conversions from class or struct types to enum,
// pointer and delegate types do not cause the right candidates to participate in
// overload resolution. It also presents numerous problems involving delegate variance
// and conversions from lambdas to delegate types.
//
// It is onerous to require the actually specified behavior. We should change the
// specification to match the previous implementation.
var operators = ArrayBuilder<UnaryOperatorSignature>.GetInstance();
this.Compilation.BuiltInOperators.GetSimpleBuiltInOperators(kind, operators, skipNativeIntegerOperators: !operand.Type.IsNativeIntegerOrNullableThereof());
GetEnumOperations(kind, operand, operators);
var pointerOperator = GetPointerOperation(kind, operand);
if (pointerOperator != null)
{
operators.Add(pointerOperator.Value);
}
CandidateOperators(isChecked, operators, operand, results, ref useSiteInfo);
operators.Free();
}
// Returns true if there were any applicable candidates.
private bool CandidateOperators(bool isChecked, ArrayBuilder<UnaryOperatorSignature> operators, BoundExpression operand, ArrayBuilder<UnaryOperatorAnalysisResult> results, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
bool anyApplicable = false;
foreach (var op in operators)
{
var conversion = Conversions.ClassifyConversionFromExpression(operand, op.OperandType, isChecked: isChecked, ref useSiteInfo);
if (conversion.IsImplicit)
{
anyApplicable = true;
results.Add(UnaryOperatorAnalysisResult.Applicable(op, conversion));
}
else
{
results.Add(UnaryOperatorAnalysisResult.Inapplicable(op, conversion));
}
}
return anyApplicable;
}
private void GetEnumOperations(UnaryOperatorKind kind, BoundExpression operand, ArrayBuilder<UnaryOperatorSignature> operators)
{
Debug.Assert(operand != null);
var enumType = operand.Type;
if ((object)enumType == null)
{
return;
}
enumType = enumType.StrippedType();
if (!enumType.IsValidEnumType())
{
return;
}
var nullableEnum = Compilation.GetOrCreateNullableType(enumType);
switch (kind)
{
case UnaryOperatorKind.PostfixIncrement:
case UnaryOperatorKind.PostfixDecrement:
case UnaryOperatorKind.PrefixIncrement:
case UnaryOperatorKind.PrefixDecrement:
case UnaryOperatorKind.BitwiseComplement:
operators.Add(new UnaryOperatorSignature(kind | UnaryOperatorKind.Enum, enumType, enumType));
operators.Add(new UnaryOperatorSignature(kind | UnaryOperatorKind.Lifted | UnaryOperatorKind.Enum, nullableEnum, nullableEnum));
break;
}
}
private static UnaryOperatorSignature? GetPointerOperation(UnaryOperatorKind kind, BoundExpression operand)
{
Debug.Assert(operand != null);
var pointerType = operand.Type as PointerTypeSymbol;
if ((object)pointerType == null)
{
return null;
}
UnaryOperatorSignature? op = null;
switch (kind)
{
case UnaryOperatorKind.PostfixIncrement:
case UnaryOperatorKind.PostfixDecrement:
case UnaryOperatorKind.PrefixIncrement:
case UnaryOperatorKind.PrefixDecrement:
op = new UnaryOperatorSignature(kind | UnaryOperatorKind.Pointer, pointerType, pointerType);
break;
}
return op;
}
// Returns true if there were any applicable candidates.
private bool GetUserDefinedOperators(UnaryOperatorKind kind, bool isChecked, BoundExpression operand, ArrayBuilder<UnaryOperatorAnalysisResult> results, ref CompoundUseSiteInfo<AssemblySymbol> useSiteInfo)
{
Debug.Assert(operand != null);
if ((object)operand.Type == null)
{
// If the operand has no type -- because it is a null reference or a lambda or a method group --
// there is no way we can determine what type to search for user-defined operators.
return false;
}
// Spec 7.3.5 Candidate user-defined operators
// SPEC: Given a type T and an operation op(A) ... the set of candidate user-defined
// SPEC: operators provided by T for op(A) is determined as follows:
// SPEC: If T is a nullable type then T0 is its underlying type; otherwise T0 is T.
// SPEC: For all operator declarations in T0 and all lifted forms of such operators, if
// SPEC: at least one operator is applicable with respect to A then the set of candidate
// SPEC: operators consists of all such applicable operators. Otherwise, if T0 is object
// SPEC: then the set of candidate operators is empty. Otherwise, the set of candidate
// SPEC: operators is the set provided by the direct base class of T0, or the effective
// SPEC: base class of T0 if T0 is a type parameter.
// https://github.com/dotnet/roslyn/issues/34451: The spec quote should be adjusted to cover operators from interfaces as well.
// From https://github.com/dotnet/csharplang/blob/main/meetings/2017/LDM-2017-06-27.md:
// - We only even look for operator implementations in interfaces if one of the operands has a type that is an interface or
// a type parameter with a non-empty effective base interface list.
// - The applicable operators from classes / structs shadow those in interfaces.This matters for constrained type parameters:
// the effective base class can shadow operators from effective base interfaces.
// - If we find an applicable candidate in an interface, that candidate shadows all applicable operators in base interfaces:
// we stop looking.
TypeSymbol type0 = operand.Type.StrippedType();
TypeSymbol constrainedToTypeOpt = type0 as TypeParameterSymbol;
// Searching for user-defined operators is expensive; let's take an early out if we can.
if (OperatorFacts.DefinitelyHasNoUserDefinedOperators(type0))
{
return false;
}
var operators = ArrayBuilder<UnaryOperatorSignature>.GetInstance();
bool hadApplicableCandidates = false;
NamedTypeSymbol current = type0 as NamedTypeSymbol;
if ((object)current == null)
{
current = type0.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteInfo);
}
if ((object)current == null && type0.IsTypeParameter())
{
current = ((TypeParameterSymbol)type0).EffectiveBaseClass(ref useSiteInfo);
}
for (; (object)current != null; current = current.BaseTypeWithDefinitionUseSiteDiagnostics(ref useSiteInfo))
{
operators.Clear();
GetUserDefinedUnaryOperatorsFromType(constrainedToTypeOpt, current, kind, isChecked, operators);
results.Clear();
if (CandidateOperators(isChecked, operators, operand, results, ref useSiteInfo))
{
hadApplicableCandidates = true;
break;
}
}
// Look in base interfaces, or effective interfaces for type parameters
if (!hadApplicableCandidates)
{
ImmutableArray<NamedTypeSymbol> interfaces = default;
if (type0.IsInterfaceType())
{
interfaces = type0.AllInterfacesWithDefinitionUseSiteDiagnostics(ref useSiteInfo);
}
else if (type0.IsTypeParameter())
{
interfaces = ((TypeParameterSymbol)type0).AllEffectiveInterfacesWithDefinitionUseSiteDiagnostics(ref useSiteInfo);
}
if (!interfaces.IsDefaultOrEmpty)
{
var shadowedInterfaces = PooledHashSet<NamedTypeSymbol>.GetInstance();
var resultsFromInterface = ArrayBuilder<UnaryOperatorAnalysisResult>.GetInstance();
results.Clear();
foreach (NamedTypeSymbol @interface in interfaces)
{
if (!@interface.IsInterface)
{
// this code could be reachable in error situations
continue;
}
if (shadowedInterfaces.Contains(@interface))
{
// this interface is "shadowed" by a derived interface
continue;
}
operators.Clear();
resultsFromInterface.Clear();
GetUserDefinedUnaryOperatorsFromType(constrainedToTypeOpt, @interface, kind, isChecked, operators);
if (CandidateOperators(isChecked, operators, operand, resultsFromInterface, ref useSiteInfo))
{
hadApplicableCandidates = true;
results.AddRange(resultsFromInterface);
// this interface "shadows" all its base interfaces
shadowedInterfaces.AddAll(@interface.AllInterfacesWithDefinitionUseSiteDiagnostics(ref useSiteInfo));
}
}
shadowedInterfaces.Free();
resultsFromInterface.Free();
}
}
operators.Free();
return hadApplicableCandidates;
}
private void GetUserDefinedUnaryOperatorsFromType(
TypeSymbol constrainedToTypeOpt,
NamedTypeSymbol type,
UnaryOperatorKind kind,
bool isChecked,
ArrayBuilder<UnaryOperatorSignature> operators)
{
Debug.Assert(operators.Count == 0);
string name1 = OperatorFacts.UnaryOperatorNameFromOperatorKind(kind, isChecked);
getDeclaredOperators(constrainedToTypeOpt, type, kind, name1, operators);
if (isChecked && SyntaxFacts.IsCheckedOperator(name1))
{
string name2 = OperatorFacts.UnaryOperatorNameFromOperatorKind(kind, isChecked: false);
var operators2 = ArrayBuilder<UnaryOperatorSignature>.GetInstance();
// Add regular operators as well.
getDeclaredOperators(constrainedToTypeOpt, type, kind, name2, operators2);
// Drop operators that have a match among the checked ones.
if (operators.Count != 0)
{
for (int i = operators2.Count - 1; i >= 0; i--)
{
foreach (UnaryOperatorSignature signature1 in operators)
{
if (SourceMemberContainerTypeSymbol.DoOperatorsPair(signature1.Method, operators2[i].Method))
{
operators2.RemoveAt(i);
break;
}
}
}
}
operators.AddRange(operators2);
operators2.Free();
}
addLiftedOperators(constrainedToTypeOpt, kind, operators);
static void getDeclaredOperators(TypeSymbol constrainedToTypeOpt, NamedTypeSymbol type, UnaryOperatorKind kind, string name, ArrayBuilder<UnaryOperatorSignature> operators)
{
foreach (MethodSymbol op in type.GetOperators(name))
{
// If we're in error recovery, we might have bad operators. Just ignore it.
if (op.ParameterCount != 1 || op.ReturnsVoid)
{
continue;
}
TypeSymbol operandType = op.GetParameterType(0);
TypeSymbol resultType = op.ReturnType;
operators.Add(new UnaryOperatorSignature(UnaryOperatorKind.UserDefined | kind, operandType, resultType, op, constrainedToTypeOpt));
}
}
void addLiftedOperators(TypeSymbol constrainedToTypeOpt, UnaryOperatorKind kind, ArrayBuilder<UnaryOperatorSignature> operators)
{
// SPEC: For the unary operators + ++ - -- ! ~ a lifted form of an operator exists
// SPEC: if the operand and its result types are both non-nullable value types.
// SPEC: The lifted form is constructed by adding a single ? modifier to the
// SPEC: operator and result types.
switch (kind)
{
case UnaryOperatorKind.UnaryPlus:
case UnaryOperatorKind.PrefixDecrement:
case UnaryOperatorKind.PrefixIncrement:
case UnaryOperatorKind.UnaryMinus:
case UnaryOperatorKind.PostfixDecrement:
case UnaryOperatorKind.PostfixIncrement:
case UnaryOperatorKind.LogicalNegation:
case UnaryOperatorKind.BitwiseComplement:
for (int i = operators.Count - 1; i >= 0; i--)
{
MethodSymbol op = operators[i].Method;
TypeSymbol operandType = op.GetParameterType(0);
TypeSymbol resultType = op.ReturnType;
if (operandType.IsValidNullableTypeArgument() &&
resultType.IsValidNullableTypeArgument())
{
operators.Add(new UnaryOperatorSignature(
UnaryOperatorKind.Lifted | UnaryOperatorKind.UserDefined | kind,
MakeNullable(operandType), MakeNullable(resultType), op, constrainedToTypeOpt));
}
}
break;
}
}
}
}
}
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