private static Expression TryRemoveNullCheck(ConditionalExpression node)
{
var binaryTest = node.Test as BinaryExpression;
if (binaryTest == null ||
!(binaryTest.NodeType == ExpressionType.Equal ||
binaryTest.NodeType == ExpressionType.NotEqual))
{
return(null);
}
var leftConstant = binaryTest.Left as ConstantExpression;
var isLeftNullConstant = leftConstant != null && leftConstant.Value == null;
var rightConstant = binaryTest.Right as ConstantExpression;
var isRightNullConstant = rightConstant != null && rightConstant.Value == null;
if (isLeftNullConstant == isRightNullConstant)
{
return(null);
}
if (binaryTest.NodeType == ExpressionType.Equal)
{
var ifTrueConstant = node.IfTrue as ConstantExpression;
if (ifTrueConstant == null || ifTrueConstant.Value != null)
{
return(null);
}
}
else
{
var ifFalseConstant = node.IfFalse as ConstantExpression;
if (ifFalseConstant == null || ifFalseConstant.Value != null)
{
return(null);
}
}
var testExpression = isLeftNullConstant ? binaryTest.Right : binaryTest.Left;
var resultExpression = binaryTest.NodeType == ExpressionType.Equal ? node.IfFalse : node.IfTrue;
var nullCheckRemovalTestingVisitor = new NullCheckRemovalTestingVisitor();
if (nullCheckRemovalTestingVisitor.CanRemoveNullCheck(testExpression, resultExpression))
{
return(resultExpression);
}
return(null);
}
/// <summary>
/// Visits a conditional expression.
/// </summary>
/// <param name="expression"> The expression to visit. </param>
/// <returns>
/// An Expression.
/// </returns>
protected override Expression VisitConditional(ConditionalExpression expression)
{
Check.NotNull(expression, nameof(expression));
if (expression.IsNullPropagationCandidate(out var testExpression, out var resultExpression) &&
_nullCheckRemovalTestingVisitor.CanRemoveNullCheck(testExpression, resultExpression))
{
return(Visit(resultExpression));
}
var test = Visit(expression.Test);
if (test?.IsSimpleExpression() == true)
{
test = Expression.Equal(test, Expression.Constant(true, typeof(bool)));
}
var ifTrue = Visit(expression.IfTrue);
var ifFalse = Visit(expression.IfFalse);
if (test != null &&
ifTrue != null &&
ifFalse != null)
{
// 'test ? new { ... } : null' case can't be translated
if (ifTrue.Type == typeof(Expression[]) ||
ifFalse.Type == typeof(Expression[]))
{
return(null);
}
if (ifTrue.IsComparisonOperation() ||
ifFalse.IsComparisonOperation())
{
var invertedTest = Invert(test);
if (invertedTest != null)
{
return(Expression.OrElse(
Expression.AndAlso(test, ifTrue),
Expression.AndAlso(invertedTest, ifFalse)));
}
}
return(expression.Update(test, ifTrue, ifFalse));
}
return(null);
}
private Expression TryRemoveNullCheck(ConditionalExpression node)
{
var binaryTest = node.Test as BinaryExpression;
if (binaryTest == null ||
!(binaryTest.NodeType == ExpressionType.Equal ||
binaryTest.NodeType == ExpressionType.NotEqual))
{
return(null);
}
var isLeftNullConstant = binaryTest.Left.IsNullConstantExpression();
var isRightNullConstant = binaryTest.Right.IsNullConstantExpression();
if (isLeftNullConstant == isRightNullConstant)
{
return(null);
}
if (binaryTest.NodeType == ExpressionType.Equal)
{
var ifTrueConstant = node.IfTrue as ConstantExpression;
if (ifTrueConstant == null ||
ifTrueConstant.Value != null)
{
return(null);
}
}
else
{
var ifFalseConstant = node.IfFalse as ConstantExpression;
if (ifFalseConstant == null ||
ifFalseConstant.Value != null)
{
return(null);
}
}
var testExpression = isLeftNullConstant ? binaryTest.Right : binaryTest.Left;
var resultExpression = binaryTest.NodeType == ExpressionType.Equal ? node.IfFalse : node.IfTrue;
var nullCheckRemovalTestingVisitor = new NullCheckRemovalTestingVisitor(_queryModelVisitor.QueryCompilationContext);
return(nullCheckRemovalTestingVisitor.CanRemoveNullCheck(testExpression, resultExpression)
? resultExpression
: null);
}
