private void UnaryOperatorEasyOut(UnaryOperatorKind kind, BoundExpression operand, UnaryOperatorOverloadResolutionResult result)
{
var operandType = operand.Type;
if (operandType == null)
{
return;
}
var easyOut = UnopEasyOut.OpKind(kind, operandType);
if (easyOut == UnaryOperatorKind.Error)
{
return;
}
UnaryOperatorSignature signature = this.Compilation.builtInOperators.GetSignature(easyOut);
Conversion? conversion = Conversions.FastClassifyConversion(operandType, signature.OperandType);
Debug.Assert(conversion.HasValue && conversion.Value.IsImplicit);
result.Results.Add(UnaryOperatorAnalysisResult.Applicable(signature, conversion.Value));
}
// 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)
{
// 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 = BetterConversionFromExpression(operand, candidates[i].Signature.OperandType, candidates[j].Signature.OperandType);
if (better == BetterResult.Left)
{
candidates[j] = candidates[j].Worse();
}
else if (better == BetterResult.Right)
{
candidates[i] = candidates[i].Worse();
}
}
}
}
public void UnaryOperatorOverloadResolution(UnaryOperatorKind kind, BoundExpression operand, UnaryOperatorOverloadResolutionResult result)
{
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:
// NOTE: In fact, for a unary operator to apply the operand must always have a type. There are no
// NOTE: unary operators that operate on lambdas, anonymous methods, method groups or null.
// 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.
GetUserDefinedOperators(kind, operand, result.Results);
// 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.
var operators = result.Results;
if (!result.AnyValid())
{
GetAllBuiltInOperators(kind, operand, result.Results);
}
// 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.
// reduce candidates
UnaryOperatorOverloadResolution(operand, result);
}
