> {- | Contains the data types and functions for annotating
>  an ast and working with annotated trees, including the
>  representations of SQL data types.
>
> Annotations:
>
> * are attached to most of the ast node data types, but not quite all of them;
>
> * types annotations are attached to most nodes during type checking;
>
> * type errors are attached to the lowest down node that the type
>   error is detected at;
>
> * nodes who fail the type check or whose type depends on a node with
>   a type error are given the type 'TypeCheckFailed';
>
> * each statement has an additional 'StatementInfo' annotation attached to it;
>
> * the parser fills in the source position annotation in every
>   annotatable ast node.
>
> -}
> module Database.HsSqlPpp.TypeChecker
>     (
>      -- * typechecking/ annotation functions
>      typeCheckStatements
>     ,typeCheckParameterizedStatement
>     ,typeCheckQueryExpr
>     ,typeCheckScalarExpr
>     ,fixUpIdentifiers
>     ,fixUpIdentifiersQE
>     ,fixUpIdentifiersSE
>     ,addExplicitCasts
>     ,canonicalizeTypeNames
>      -- * Annotated tree utils
>     ,getStatementAnnotations
>     ) where
>
> import Database.HsSqlPpp.Internals.AstInternal
> import Database.HsSqlPpp.Internals.TypeChecking.Utils
> --import Database.HsSqlPpp.Internals.AstAnnotation
> import Database.HsSqlPpp.Internals.AnnotationUtils