// Takes a list of candidates and mutates the list to throw out the ones that are worse than
// another applicable candidate.
private void BinaryOperatorOverloadResolution(
BoundExpression left,
BoundExpression right,
BinaryOperatorOverloadResolutionResult result,
ref HashSet<DiagnosticInfo> useSiteDiagnostics)
{
// 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.GetValidCount() == 1)
{
return;
}
// 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.
// UNDONE: This is a naive quadratic algorithm; there is a linear algorithm that works. Consider using it.
var candidates = result.Results;
for (int i = 0; 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 < candidates.Count; ++j)
{
if (i == j)
{
continue;
}
if (candidates[j].Kind == OperatorAnalysisResultKind.Inapplicable)
{
continue;
}
var better = BetterOperator(candidates[i].Signature, candidates[j].Signature, left, right, ref useSiteDiagnostics);
if (better == BetterResult.Left)
{
candidates[j] = candidates[j].Worse();
}
else if (better == BetterResult.Right)
{
candidates[i] = candidates[i].Worse();
}
}
}
}
public void BinaryOperatorOverloadResolution(BinaryOperatorKind kind, BoundExpression left, BoundExpression right, BinaryOperatorOverloadResolutionResult result, ref HashSet<DiagnosticInfo> useSiteDiagnostics)
{
Debug.Assert(left != null);
Debug.Assert(right != null);
Debug.Assert(result.Results.Count == 0);
// SPEC: An operation of the form x&&y or x||y is processed by applying overload resolution
// SPEC: as if the operation was written x&y or x|y.
// SPEC VIOLATION: For compatibility with Dev11, do not apply this rule to built-in conversions.
BinaryOperatorKind underlyingKind = kind & ~BinaryOperatorKind.Logical;
// We can do a table lookup for well-known problems in overload resolution.
BinaryOperatorEasyOut(underlyingKind, left, right, result);
if (result.Results.Count > 0)
{
return;
}
// The following is a slight rewording of the specification to emphasize that not all
// operands of a binary operation need to have a type.
// SPEC: An operation of the form x op y, where op is an overloadable binary operator is processed as follows:
// SPEC: The set of candidate user-defined operators provided by the types (if any) of x and y for the
// SPEC operation operator op(x, y) is determined.
bool hadUserDefinedCandidate = GetUserDefinedOperators(underlyingKind, left, right, result.Results, ref useSiteDiagnostics);
// SPEC: If the set of candidate user-defined operators is not empty, then this becomes the set of candidate
// SPEC: operators for the operation. Otherwise, the predefined binary operator op implementations, including
// SPEC: their lifted forms, become the set of candidate operators for the operation.
// Note that the native compiler has a bug in its binary operator overload resolution involving
// lifted built-in operators. The spec says that we should add the lifted and unlifted operators
// to a candidate set, eliminate the inapplicable operators, and then choose the best of what is left.
// The lifted operator is defined as, say int? + int? --> int?. That is not what the native compiler
// does. The native compiler, rather, effectively says that there are *three* lifted operators:
// int? + int? --> int?, int + int? --> int? and int? + int --> int?, and it chooses the best operator
// amongst those choices.
//
// This is a subtle difference; most of the time all it means is that we generate better code because we
// skip an unnecessary operand conversion to int? when adding int to int?. But some of the time it
// means that a different user-defined conversion is chosen than the one you would expect, if the
// operand has a user-defined conversion to both int and int?.
//
// Roslyn matches the specification and takes the break from the native compiler.
if (!hadUserDefinedCandidate)
{
result.Results.Clear();
GetAllBuiltInOperators(kind, left, right, result.Results, ref useSiteDiagnostics);
}
// SPEC: The overload resolution rules of 7.5.3 are applied to the set of candidate operators to select the best
// SPEC: operator with respect to the argument list (x, y), and this operator becomes the result of the overload
// SPEC: resolution process. If overload resolution fails to select a single best operator, a binding-time
// SPEC: error occurs.
BinaryOperatorOverloadResolution(left, right, result, ref useSiteDiagnostics);
}
private void BinaryOperatorEasyOut(BinaryOperatorKind kind, BoundExpression left, BoundExpression right, BinaryOperatorOverloadResolutionResult result)
{
var leftType = left.Type;
if ((object)leftType == null)
{
return;
}
var rightType = right.Type;
if ((object)rightType == null)
{
return;
}
if (PossiblyUnusualConstantOperation(left, right))
{
return;
}
var easyOut = BinopEasyOut.OpKind(kind, leftType, rightType);
if (easyOut == BinaryOperatorKind.Error)
{
return;
}
BinaryOperatorSignature signature = this.Compilation.builtInOperators.GetSignature(easyOut);
Conversion leftConversion = Conversions.FastClassifyConversion(left.Type, signature.LeftType);
Conversion rightConversion = Conversions.FastClassifyConversion(right.Type, signature.RightType);
Debug.Assert(leftConversion.Exists && leftConversion.IsImplicit);
Debug.Assert(rightConversion.Exists && rightConversion.IsImplicit);
result.Results.Add(BinaryOperatorAnalysisResult.Applicable(signature, leftConversion, rightConversion));
}
private void BinaryOperatorEasyOut(BinaryOperatorKind kind, BoundExpression left, BoundExpression right, BinaryOperatorOverloadResolutionResult result)
{
var leftType = left.Type;
if (leftType is null)
{
return;
}
var rightType = right.Type;
if (rightType is null)
{
return;
}
if (PossiblyUnusualConstantOperation(left, right))
{
return;
}
var easyOut = BinopEasyOut.OpKind(kind, leftType, rightType);
if (easyOut == BinaryOperatorKind.Error)
{
return;
}
BinaryOperatorSignature signature = this.Compilation.builtInOperators.GetSignature(easyOut);
Conversion leftConversion = Conversions.FastClassifyConversion(leftType, signature.LeftType);
Conversion rightConversion = Conversions.FastClassifyConversion(rightType, signature.RightType);
Debug.Assert(leftConversion.Exists && leftConversion.IsImplicit);
Debug.Assert(rightConversion.Exists && rightConversion.IsImplicit);
result.Results.Add(BinaryOperatorAnalysisResult.Applicable(signature, leftConversion, rightConversion));
}
private bool VOStructBinaryOperatorComparison(BinaryOperatorKind kind, BoundExpression left, BoundExpression right, BinaryOperatorOverloadResolutionResult result)
{
if (left.Type == right.Type)
{
bool isVoStruct = false;
if (left.Type.IsPointerType())
{
var pt = left.Type as PointerTypeSymbol;
isVoStruct = pt.PointedAtType.IsVoStructOrUnion();
}
else
{
isVoStruct = left.Type.IsVoStructOrUnion();
}
if (isVoStruct && (kind == BinaryOperatorKind.Equal || kind == BinaryOperatorKind.NotEqual))
{
BinaryOperatorSignature sig = new BinaryOperatorSignature(kind, left.Type, right.Type, Compilation.GetSpecialType(SpecialType.System_Boolean));
BinaryOperatorAnalysisResult best = BinaryOperatorAnalysisResult.Applicable(sig, Conversion.Identity, Conversion.Identity);
result.Results.Clear();
result.Results.Add(best);
return(true);
}
}
return(false);
}