Avoid unnecessary CompilableProvier castings (#84)

Orm/Xtensive.Orm/Orm/Linq/Expressions/Visitors/ExtendedExpressionReplacer.cs

@@ -72,7 +72,7 @@ protected override Expression VisitSubQueryExpression(SubQueryExpression express
       return expression;
     }
 
-    private Expression TranslateExpression(Provider provider, Expression original)
+    private Expression TranslateExpression(CompilableProvider provider, Expression original)
     {
       var result = Visit(original);
       return result ?? original;

Orm/Xtensive.Orm/Orm/Linq/Rewriters/ApplyParameterToTupleParameterRewriter.cs

@@ -74,7 +74,7 @@ protected override Expression VisitSubQueryExpression(SubQueryExpression express
       return expression;
     }
 
-    private Expression RewriteExpression(Provider provider, Expression expression)
+    private Expression RewriteExpression(CompilableProvider provider, Expression expression)
     {
       return Visit(expression);
     }

Orm/Xtensive.Orm/Orm/Linq/Rewriters/SubqueryFilterRemover.cs

@@ -95,7 +95,7 @@ public SubqueryFilterChecker(ApplyParameter filterParameter)
 
     private readonly SubqueryFilterChecker checker;
 
-    protected override Provider VisitFilter(FilterProvider provider)
+    protected override CompilableProvider VisitFilter(FilterProvider provider)
     {
       return checker.Check(provider.Predicate.Body)
         ? provider.Source

Orm/Xtensive.Orm/Orm/Providers/SessionHandler.References.cs

@@ -92,7 +92,7 @@ private static IEnumerable<ReferenceInfo> FindReferences(Entity owner, Associati
 
     private static (CompilableProvider, Parameter<Tuple>) BuildReferencingQuery(AssociationInfo association)
     {
-      var provider = (CompilableProvider)null;
+      CompilableProvider provider = null;
       var parameter = new Parameter<Tuple>("pTuple");
       switch (association.Multiplicity) {
         case Multiplicity.ZeroToOne:
@@ -128,7 +128,7 @@ private static (CompilableProvider, Parameter<Tuple>) BuildReferencingQuery(Asso
               parameter))
             .Alias("a")
             .Join(
-              index.GetQuery(), 
+              index.GetQuery(),
               association.Reversed.OwnerField.MappingInfo
                 .GetItems()
                 .Select((l,r) => new Pair<int>(l,r))

Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.cs

@@ -382,11 +382,9 @@ protected override SqlProvider VisitSort(SortProvider provider)
     /// <inheritdoc/>
     protected override SqlProvider VisitStore(StoreProvider provider)
     {
-      var source =
-        provider.Source as ExecutableProvider
-          ?? (provider.Source is RawProvider
-            ? (ExecutableProvider) (new Rse.Providers.ExecutableRawProvider((RawProvider) provider.Source))
-            : Compile((CompilableProvider) provider.Source));
+      var source = provider.Source is RawProvider rawProvider
+            ? (ExecutableProvider) (new Rse.Providers.ExecutableRawProvider(rawProvider))
+            : Compile(provider.Source);
       var columnNames = provider.Header.Columns.Select(column => column.Name).ToArray();
       var descriptor = DomainHandler.TemporaryTableManager
         .BuildDescriptor(Mapping, provider.Name, provider.Header.TupleDescriptor, columnNames);

Orm/Xtensive.Orm/Orm/Rse/Providers/Compilable/StoreProvider.cs

@@ -21,12 +21,12 @@ public sealed class StoreProvider : CompilableProvider
     /// <summary>
     /// Gets the name of saved data.
     /// </summary>
-    public string Name { get; private set; }
+    public string Name { get; }
 
     /// <summary>
     /// Source provider.
     /// </summary>
-    public Provider Source { get; private set; }
+    public CompilableProvider Source { get; }
 
     /// <inheritdoc/>
     protected override RecordSetHeader BuildHeader()
@@ -66,7 +66,7 @@ public StoreProvider(RecordSetHeader header, string name)
     /// </summary>
     /// <param name="source">The <see cref="Source"/> property value.</param>
     /// <param name="name">The <see cref="Name"/> property value.</param>
-    public StoreProvider(Provider source, string name)
+    public StoreProvider(CompilableProvider source, string name)
       : base(ProviderType.Store, source)
     {
       ArgumentValidator.EnsureArgumentNotNull(source, "source");
@@ -84,7 +84,7 @@ public StoreProvider(Provider source, string name)
     /// Initializes a new instance of this class.
     /// </summary>
     /// <param name="source">The <see cref="Source"/> property value.</param>
-    public StoreProvider(Provider source)
+    public StoreProvider(CompilableProvider source)
       : base(ProviderType.Store, source)
     {
       ArgumentValidator.EnsureArgumentNotNull(source, "source");