private BoundExpression BindBooleanExpression(ExpressionSyntax node)
{
// A boolean-expression is an expression that yields a result of type bool;
// either directly or through application of operator true in certain
// contexts as specified in the following.
//
// The controlling conditional expression of an if-statement, while-statement,
// do-statement, or for-statement is a boolean-expression. The controlling
// conditional expression of the ?: operator follows the same rules as a
// boolean-expression, but for reasons of operator precedence is classified
// as a conditional-or-expression.
//
// A boolean-expression is required to be implicitly convertible to bool
// or of a type that implements operator true. If neither requirement
// is satisfied, a binding-time error occurs.
//
// When a boolean expression cannot be implicitly converted to bool but does
// implement operator true, then following evaluation of the expression,
// the operator true implementation provided by that type is invoked
// to produce a bool value.
var expr = BindExpression(node);
if (!expr.IsOK)
{
// The expression could not be bound. Insert a fake conversion
// around it to bool and keep on going.
return(BoundConversion.AsError(null, expr, ConversionKind.NoConversion, false, false, System_Boolean));
}
var kind = Conversions.ClassifyConversion(expr, System_Boolean);
if (kind.IsImplicitConversion())
{
if (kind == ConversionKind.Identity)
{
return(expr);
}
else
{
return(new BoundConversion(null, expr, kind, false, false, System_Boolean));
}
}
// UNDONE: check for operator true / operator false
// UNDONE: give appropriate errors.
return(null);
}
private BoundExpression ConvertToArrayIndex(BoundExpression index)
{
Debug.Assert(index != null);
var result =
TryImplicitConversion(index, System_Int32) ??
TryImplicitConversion(index, System_UInt32) ??
TryImplicitConversion(index, System_Int64) ??
TryImplicitConversion(index, System_UInt64);
if (result == null)
{
// UNDONE: Give the error that would be given upon conversion to int32.
return(BoundConversion.AsError(index.Syntax, index, ConversionKind.NoConversion, false, false, System_Int32));
}
return(result);
}