private BoundExpression BindCoalesceExpression(CoalesceExpressionSyntax node)
{
// COALESCE(e1, e2, .. eN)
//
// ====>
//
// CASE
// WHEN e1 IS NOT NULL THEN e1
// ..
// WHEN e2 IS NOT NULL THEN e2
// ELSE
// eN
// END
var boundArguments = BindToCommonType(node.ArgumentList.Arguments);
var caseLabelCount = node.ArgumentList.Arguments.Count - 1;
var caseLabels = new BoundCaseLabel[caseLabelCount];
for (var i = 0; i < caseLabelCount; i++)
{
var argument = node.ArgumentList.Arguments[i];
var boundArgument = boundArguments[i];
var boundIsNullExpression = new BoundIsNullExpression(boundArgument);
var boundIsNullNegation = BindUnaryExpression(argument.Span, UnaryOperatorKind.LogicalNot, boundIsNullExpression);
var caseLabel = new BoundCaseLabel(boundIsNullNegation, boundArgument);
caseLabels[i] = caseLabel;
}
var elseExpresion = boundArguments.Last();
return(new BoundCaseExpression(caseLabels, elseExpresion));
}
private BoundExpression BindNullIfExpression(NullIfExpressionSyntax node)
{
// NULLIF(left, right)
//
// ===>
//
// CASE WHEN left != right THEN left END
var expressions = BindToCommonType(new[] { node.LeftExpression, node.RightExpression });
var boundLeft = expressions[0];
var boundRight = expressions[1];
var boundComparison = BindBinaryExpression(node.Span, BinaryOperatorKind.NotEqual, boundLeft, boundRight);
var boundCaseLabel = new BoundCaseLabel(boundComparison, boundLeft);
return(new BoundCaseExpression(new[] { boundCaseLabel }, null));
}
protected virtual BoundCaseLabel RewriteCaseLabel(BoundCaseLabel node)
{
return(node.Update(RewriteExpression(node.Condition),
RewriteExpression(node.ThenExpression)));
}