private ImmutableArray <BoundExpression> BindCaseResultExpressions(CaseExpressionSyntax node)
{
var elseExpression = node.ElseLabel == null
? Enumerable.Empty <ExpressionSyntax>()
: new[] { node.ElseLabel.Expression };
var expressions = node.CaseLabels.Select(l => l.ThenExpression).Concat(elseExpression).ToImmutableArray();
return(BindToCommonType(expressions));
}
private BoundExpression BindRegularCase(CaseExpressionSyntax node)
{
// CASE
// WHEN e1 THEN r1
// WHEN e2 THEN r2
// ...
// ELSE re
// END CASE
var boundResults = BindCaseResultExpressions(node);
var boundCaseLabels = node.CaseLabels.Select((l, i) => new BoundCaseLabel(BindExpression(l.WhenExpression), boundResults[i])).ToImmutableArray();
var boundElse = node.ElseLabel == null
? null
: boundResults.Last();
EnsureCaseLabelsEvaluateToBool(node.CaseLabels, boundCaseLabels);
return(new BoundCaseExpression(boundCaseLabels, boundElse));
}
private BoundExpression BindSearchedCase(CaseExpressionSyntax node)
{
// CASE x
// WHEN e1 THEN r1
// WHEN e2 THEN r2
// ...
// ELSE re
// END CASE
//
// ==>
//
// CASE
// WHEN x = e1 THEN r1
// WHEN x = e2 THEN r2
// ...
// ELSE re
// END CASE
var boundInput = BindExpression(node.InputExpression);
var boundResults = BindCaseResultExpressions(node);
var boundCaseLabels = (from t in node.CaseLabels.Select((c, i) => Tuple.Create(c, i))
let caseLabel = t.Item1
let i = t.Item2
let boundWhen = BindExpression(caseLabel.WhenExpression)
let boundCondition = BindBinaryExpression(caseLabel.WhenExpression.Span, BinaryOperatorKind.Equal, boundInput, boundWhen)
let boundThen = boundResults[i]
select new BoundCaseLabel(boundCondition, boundThen)).ToImmutableArray();
var boundElse = node.ElseLabel == null
? null
: boundResults.Last();
EnsureCaseLabelsEvaluateToBool(node.CaseLabels, boundCaseLabels);
return(new BoundCaseExpression(boundCaseLabels, boundElse));
}
public virtual void VisitCaseExpression(CaseExpressionSyntax node)
{
DefaultVisit(node);
}
private BoundExpression BindCaseExpression(CaseExpressionSyntax node)
{
return(node.InputExpression == null
? BindRegularCase(node)
: BindSearchedCase(node));
}
public virtual TResult VisitCaseExpression(CaseExpressionSyntax node)
{
return(DefaultVisit(node));
}
