private ConstantValue FoldUnaryOperator(
CSharpSyntaxNode syntax,
UnaryOperatorKind kind,
BoundExpression operand,
SpecialType resultType,
DiagnosticBag diagnostics)
{
Debug.Assert(operand != null);
// UNDONE: report errors when in a checked context.
if (operand.HasAnyErrors)
{
return null;
}
var value = operand.ConstantValue;
if (value == null || value.IsBad)
{
return value;
}
if (kind.IsEnum() && !kind.IsLifted())
{
return FoldEnumUnaryOperator(syntax, kind, operand, diagnostics);
}
var newValue = FoldNeverOverflowUnaryOperator(kind, value);
if (newValue != null)
{
return ConstantValue.Create(newValue, resultType);
}
if (CheckOverflowAtCompileTime)
{
try
{
newValue = FoldCheckedIntegralUnaryOperator(kind, value);
}
catch (OverflowException)
{
Error(diagnostics, ErrorCode.ERR_CheckedOverflow, syntax);
return ConstantValue.Bad;
}
}
else
{
newValue = FoldUncheckedIntegralUnaryOperator(kind, value);
}
if (newValue != null)
{
return ConstantValue.Create(newValue, resultType);
}
return null;
}