/// <summary>
/// We only support a sub-class of expressions for now - so we'd better make sure we are protected!
/// </summary>
/// <param name="expression"></param>
/// <returns></returns>
protected override Expression VisitConditional(ConditionalExpression expression)
{
// We can support complex sub-expressions so long as they don't leak out of the
// comparison.
if (expression.Type.IsClass &&
(
CheckForSubQueries.CheckExpression(expression.IfFalse) ||
CheckForSubQueries.CheckExpression(expression.IfTrue))
)
{
throw new NotSupportedException(string.Format("Complex true/false clauses in a conditional expression are not supported: '{0}'", expression.ToString()));
}
// If this is a class as a result, then we can't do much extra processing here. So skip.
if (expression.Type.IsClass)
{
return(base.VisitConditional(expression));
}
// Run the code for the test, and then create the if/then/else that will support it.
var testExpression = base.Visit(expression.Test);
var testExpressionEvaluation = ExpressionToCPP.GetExpression(testExpression, GeneratedCode, CodeContext, MEFContainer);
var testBoolInCode = testExpressionEvaluation is DeclarableParameter p ? p : DeclarableParameter.CreateDeclarableParameterExpression(typeof(bool));
if (testBoolInCode != testExpressionEvaluation)
{
GeneratedCode.Add(testBoolInCode);
GeneratedCode.Add(new Statements.StatementAssign(testBoolInCode, testExpressionEvaluation));
}
// The result
var conditionalResult = DeclarableParameter.CreateDeclarableParameterExpression(expression.Type);
GeneratedCode.Add(conditionalResult);
// Do the if true statement
var topScope = GeneratedCode.CurrentScope;
GeneratedCode.Add(new Statements.StatementFilter(testBoolInCode));
var iftrueExpression = Visit(expression.IfTrue);
GeneratedCode.Add(new Statements.StatementAssign(conditionalResult, ExpressionToCPP.GetExpression(iftrueExpression, GeneratedCode, CodeContext, MEFContainer)));
GeneratedCode.CurrentScope = topScope;
// Do the if false statement
GeneratedCode.Add(new Statements.StatementFilter(ExpressionToCPP.GetExpression(Expression.Not(testBoolInCode), GeneratedCode, CodeContext, MEFContainer)));
var ifFalseExpression = Visit(expression.IfFalse);
GeneratedCode.Add(new Statements.StatementAssign(conditionalResult, ExpressionToCPP.GetExpression(ifFalseExpression, GeneratedCode, CodeContext, MEFContainer)));
GeneratedCode.CurrentScope = topScope;
// Consider this expression now transformed, so return the result, not
// the conditional expression itself.
return(conditionalResult);
}
