Checks for ternary and coalesce operators

Author: alex-kulakov

Orm/Xtensive.Orm/Orm/Linq/Translator.Expressions.cs

@@ -190,6 +190,23 @@ protected override Expression VisitBinary(BinaryExpression binaryExpression)
             : Visit(binaryExpression.Right);
         }
       }
+      else if (memberType == MemberType.Entity || memberType == MemberType.Structure) {
+        if (binaryExpression.NodeType == ExpressionType.Coalesce) {
+          if ((context.Evaluator.CanBeEvaluated(binaryExpression.Right) && !(binaryExpression.Right is ConstantExpression))
+            || (context.Evaluator.CanBeEvaluated(binaryExpression.Left) && !(binaryExpression.Left is ConstantExpression)))
+            throw new NotSupportedException(
+              string.Format("Coalesce expressions with constant values of {0} type are not supported", memberType.ToString()));
+
+          return Visit(Expression.Condition(
+            Expression.NotEqual(binaryExpression.Left, Expression.Constant(null)),
+            binaryExpression.Left,
+            binaryExpression.Right));
+        }
+        else {
+          left = Visit(binaryExpression.Left);
+          right = Visit(binaryExpression.Right);
+        }
+      }
       else {
         left = Visit(binaryExpression.Left);
         right = Visit(binaryExpression.Right);
@@ -216,6 +233,19 @@ protected override Expression VisitBinary(BinaryExpression binaryExpression)
       return resultBinaryExpression;
     }
 
+    protected override Expression VisitConditional(ConditionalExpression c)
+    {
+      var memberType = c.IfTrue.Type == typeof(object)
+        ? c.IfFalse.GetMemberType()
+        : c.IfTrue.GetMemberType();
+      if (memberType == MemberType.Entity || memberType == MemberType.Structure) {
+        if ((context.Evaluator.CanBeEvaluated(c.IfFalse) && !(c.IfFalse is ConstantExpression))
+          || (context.Evaluator.CanBeEvaluated(c.IfTrue) && !(c.IfTrue is ConstantExpression)))
+          throw new NotSupportedException(string.Format("Conditional expressions with constant values of {0} type are not supported.", memberType.ToString()));
+      }
+      return base.VisitConditional(c);
+    }
+
     private Expression ConvertEnum(Expression left)
     {
       var underlyingType = Enum.GetUnderlyingType(left.Type.StripNullable());