private SqlExpression SimplifyUnaryExpression(
ExpressionType operatorType,
SqlExpression operand,
Type type,
RelationalTypeMapping typeMapping)
{
switch (operatorType)
{
case ExpressionType.Not
when type == typeof(bool):
{
switch (operand)
{
// !(true) -> false
// !(false) -> true
case SqlConstantExpression constantOperand
when constantOperand.Value is bool value:
{
return(_sqlExpressionFactory.Constant(!value, typeMapping));
}
case InExpression inOperand:
return(inOperand.Negate());
case SqlUnaryExpression unaryOperand:
switch (unaryOperand.OperatorType)
{
// !(!a) -> a
case ExpressionType.Not:
return(unaryOperand.Operand);
//!(a IS NULL) -> a IS NOT NULL
case ExpressionType.Equal:
return(_sqlExpressionFactory.IsNotNull(unaryOperand.Operand));
//!(a IS NOT NULL) -> a IS NULL
case ExpressionType.NotEqual:
return(_sqlExpressionFactory.IsNull(unaryOperand.Operand));
}
break;
case SqlBinaryExpression binaryOperand:
{
// De Morgan's
if (binaryOperand.OperatorType == ExpressionType.AndAlso ||
binaryOperand.OperatorType == ExpressionType.OrElse)
{
var newLeft = SimplifyUnaryExpression(ExpressionType.Not, binaryOperand.Left, type, typeMapping);
var newRight = SimplifyUnaryExpression(ExpressionType.Not, binaryOperand.Right, type, typeMapping);
return(SimplifyLogicalSqlBinaryExpression(
binaryOperand.OperatorType == ExpressionType.AndAlso
? ExpressionType.OrElse
: ExpressionType.AndAlso,
newLeft,
newRight,
binaryOperand.TypeMapping !));
}
// those optimizations are only valid in 2-value logic
// they are safe to do here because if we apply null semantics
// because null semantics removes possibility of nulls in the tree when the comparison is wrapped around NOT
if (!_useRelationalNulls &&
TryNegate(binaryOperand.OperatorType, out var negated))
{
return(SimplifyBinaryExpression(
negated,
binaryOperand.Left,
binaryOperand.Right,
binaryOperand.TypeMapping !));
}
}
break;
}
break;
}
case ExpressionType.Equal:
case ExpressionType.NotEqual:
return(SimplifyNullNotNullExpression(
operatorType,
operand,
type,
typeMapping));
}
return(_sqlExpressionFactory.MakeUnary(operatorType, operand, type, typeMapping) !);
}
