RC2, using ?? operator in select fails with casting error

[sadjadbp]

RC2, using ?? operator in select fails with casting error.

.Select(x => x.NullableBooleanProperty ?? false)

would fail with casting error. But the same like this is ok

.Select(x => x.NullableBooleanProperty == null ? false : x.NullableBooleanProperty.value)

[mikary]

The invalid cast exception is the result of a general problem with materialization and SQL Server. There are a few different ways to compensate for this issue:

1. Compensate in SQL generation by always casting bool literals to BIT (original proposed solution in Fix #5439 - Select null coalesce bool throws InvalidCastException #5523)
   • This is the most general solution to the problem, but introduces unnecessary CASTs into the SQL where results are not required.
   • The new behavior may be introduced through the RelationalSqlGenerationHelper or SqlServerSqlGenerationHelper (Possible to move all bit casts to SQL Server implementation, probably requires a "providers-beware").
   • The current implementation for DefaultQuerySqlGenerator.VisitConditional does similar compensation for this issue and could be simplified by this implementation
2. Detect and compensate for bool casts in materialization
   • Adds additional check / cast logic when using the ValueBuffer that could prevent the exception from being thrown in all int to bool cast cases, but potentially has a negitive performance impact on a very hot path
3. Modify the DefaultQuerySqlGenerator and or SqlServerQuerySqlGenerator to special case on bool values
   • Introduces logic in SQL generation to compensate for bool values in the projection expressions
   • May not be feasible without modifying the expression due to AliasExpressions (generating a cast around an alias results in invalid SQL)
4. Alter the expression before SQL generation (i.e. in RelationalProjectionExpressionVisitor)
   • Requires introducing a new Expression node / ExpressionType to provide a Convert expression that can be distinguished from existing converts (current SQL generation ignores Convert operations to avoid unnecessary casts)

[smitpatel]

Already fixed in RTM. Adding test.

[smitpatel]

dupe of #5652