Merge pull request #261 from servicetitan/upstream/covariantReturnTypes

Use C#9 Covariant return types feature for Clone() implementation for type safety and reduce number of casts

Author: alex-kulakov

Orm/Xtensive.Orm.Tests.Sql/CloneTests.cs

@@ -37,7 +37,7 @@ public void SetUp()
     public void SqlExpressionCloneTest()
     {
       SqlExpression e = SqlDml.Literal(1);
-      SqlExpression eClone = (SqlExpression) e.Clone();
+      SqlExpression eClone = e.Clone();
       Assert.AreNotEqual(e, eClone);
       Assert.AreEqual(e.NodeType, eClone.NodeType);
     }

Orm/Xtensive.Orm/Orm/Upgrade/Internals/CatalogCloner.cs

@@ -84,7 +84,7 @@ private void CloneSchemas(Catalog newCatalog, Catalog source, Dictionary<string,
     private void CloneAssertions(Schema newSchema, Schema sourceSchema)
     {
       foreach (var assertion in sourceSchema.Assertions) {
-        var newAssertion = newSchema.CreateAssertion(assertion.Name, (SqlExpression)assertion.Condition.Clone(), assertion.IsDeferrable, assertion.IsInitiallyDeferred);
+        var newAssertion = newSchema.CreateAssertion(assertion.Name, assertion.Condition.Clone(), assertion.IsDeferrable, assertion.IsInitiallyDeferred);
         CopyDbName(newAssertion, assertion);
       }
     }
@@ -113,9 +113,9 @@ private void CloneDomains(Schema newSchema, Schema sourceSchema, Dictionary<Coll
         if (sourceDomain.Collation!=null)
           newDomain.Collation = collationsMap[sourceDomain.Collation];
         if (sourceDomain.DefaultValue!=null)
-          newDomain.DefaultValue = (SqlExpression)sourceDomain.DefaultValue.Clone();
+          newDomain.DefaultValue = sourceDomain.DefaultValue.Clone();
         foreach (var domainConstraint in sourceDomain.DomainConstraints) {
-          var newConstraint = newDomain.CreateConstraint(domainConstraint.Name, (SqlExpression) domainConstraint.Condition.Clone());
+          var newConstraint = newDomain.CreateConstraint(domainConstraint.Name, domainConstraint.Condition.Clone());
           CopyDbName(newConstraint, domainConstraint);
         }
       }
@@ -181,7 +181,7 @@ private void CloneTableColumns(Table newTable, Table sourceTable, Dictionary<Col
         CopyDbName(newColumn, sourceTableColumn);
 
         if (sourceTableColumn.DefaultValue!=null)
-          newColumn.DefaultValue = (SqlExpression) sourceTableColumn.DefaultValue.Clone();
+          newColumn.DefaultValue = sourceTableColumn.DefaultValue.Clone();
 
         var schema = newTable.Schema;
         if (sourceTableColumn.Collation!=null) {
@@ -196,7 +196,7 @@ private void CloneTableColumns(Table newTable, Table sourceTable, Dictionary<Col
         if (sourceTableColumn.Domain!=null)
           newColumn.Domain = schema.Domains[sourceTableColumn.Domain.Name];
         if (sourceTableColumn.Expression!=null)
-          newColumn.Expression = (SqlExpression) sourceTableColumn.Expression.Clone();
+          newColumn.Expression = sourceTableColumn.Expression.Clone();
         newColumn.IsNullable = sourceTableColumn.IsNullable;
         newColumn.IsPersisted = sourceTableColumn.IsPersisted;
         if (sourceTableColumn.SequenceDescriptor!=null)
@@ -251,7 +251,7 @@ private void CloneIndex(DataTable newTable, Index sourceIndex)
         ft.IsUnique = ftIndex.IsUnique;
         ft.UnderlyingUniqueIndex = ftIndex.UnderlyingUniqueIndex;
         if (ftIndex.Where!=null)
-          ft.Where = (SqlExpression) ftIndex.Where.Clone();
+          ft.Where = ftIndex.Where.Clone();
         ClonePartitionDescriptor(ft, sourceIndex);
         return;
       }
@@ -269,7 +269,7 @@ private void CloneIndex(DataTable newTable, Index sourceIndex)
         spatial.IsClustered = spatialIndex.IsClustered;
         spatial.IsUnique = spatialIndex.IsUnique;
         if (spatialIndex.Where!=null)
-          spatial.Where = (SqlExpression) spatialIndex.Where.Clone();
+          spatial.Where = spatialIndex.Where.Clone();
         ClonePartitionDescriptor(spatialIndex, sourceIndex);
         return;
       }
@@ -283,7 +283,7 @@ private void CloneIndex(DataTable newTable, Index sourceIndex)
       index.IsUnique = sourceIndex.IsUnique;
       index.IsClustered = sourceIndex.IsClustered;
       if (sourceIndex.Where!=null)
-        index.Where = (SqlExpression) sourceIndex.Where.Clone();
+        index.Where = sourceIndex.Where.Clone();
       index.NonkeyColumns.AddRange(GetNonKeyColumns(newTable, sourceIndex));
       index.IsBitmap = sourceIndex.IsBitmap;
       ClonePartitionDescriptor(index, sourceIndex);
@@ -319,7 +319,7 @@ private void CloneTableConstraint(Table newTable, TableConstraint sourceConstrai
     {
       var checkConstraint = sourceConstraint as CheckConstraint;
       if (checkConstraint!=null) {
-        var c = newTable.CreateCheckConstraint(checkConstraint.Name, (SqlExpression) checkConstraint.Condition.Clone());
+        var c = newTable.CreateCheckConstraint(checkConstraint.Name, checkConstraint.Condition.Clone());
         CopyDbName(c, checkConstraint);
         return;
       }

Orm/Xtensive.Orm/Sql/Ddl/Actions/SqlAddColumn.cs

@@ -12,10 +12,9 @@ public class SqlAddColumn : SqlAction
   {
     public TableColumn Column { get; private set; }
 
-    internal override object Clone(SqlNodeCloneContext context) =>
-      context.NodeMapping.TryGetValue(this, out var clone)
-        ? clone
-        : context.NodeMapping[this] = new SqlAddColumn(Column);
+    internal override SqlAddColumn Clone(SqlNodeCloneContext context) =>
+      context.GetOrAdd(this, static (t, c) =>
+        new SqlAddColumn(t.Column));
 
     // Constructors
 

Orm/Xtensive.Orm/Sql/Ddl/Actions/SqlAddConstraint.cs

@@ -12,10 +12,9 @@ public class SqlAddConstraint : SqlAction
   {
     public Constraint Constraint { get; private set; }
 
-    internal override object Clone(SqlNodeCloneContext context) =>
-      context.NodeMapping.TryGetValue(this, out var clone)
-        ? clone
-        : context.NodeMapping[this] = new SqlAddConstraint(Constraint);
+    internal override SqlAddConstraint Clone(SqlNodeCloneContext context) =>
+      context.GetOrAdd(this, static (t, c) =>
+        new SqlAddConstraint(t.Constraint));
 
     // Constructors
 

Orm/Xtensive.Orm/Sql/Ddl/Actions/SqlAlterIdentityInfo.cs

@@ -14,10 +14,9 @@ public class SqlAlterIdentityInfo : SqlAction
     public SequenceDescriptor SequenceDescriptor { get; set; }
     public SqlAlterIdentityInfoOptions InfoOption { get; set; }
 
-    internal override object Clone(SqlNodeCloneContext context) =>
-      context.NodeMapping.TryGetValue(this, out var clone)
-        ? clone
-        : context.NodeMapping[this] = new SqlAlterIdentityInfo(Column, (SequenceDescriptor) SequenceDescriptor.Clone(), InfoOption);
+    internal override SqlAlterIdentityInfo Clone(SqlNodeCloneContext context) =>
+      context.GetOrAdd(this, static (t, c) =>
+        new SqlAlterIdentityInfo(t.Column, (SequenceDescriptor) t.SequenceDescriptor.Clone(), t.InfoOption));
 
     internal SqlAlterIdentityInfo(TableColumn column, SequenceDescriptor sequenceDescriptor, SqlAlterIdentityInfoOptions infoOption)
     {

Orm/Xtensive.Orm/Sql/Ddl/Actions/SqlDropColumn.cs

@@ -12,10 +12,9 @@ public class SqlDropColumn : SqlCascadableAction
   {
     public TableColumn Column { get; private set; }
 
-    internal override object Clone(SqlNodeCloneContext context) =>
-      context.NodeMapping.TryGetValue(this, out var clone)
-        ? clone
-        : context.NodeMapping[this] = new SqlDropColumn(Column);
+    internal override SqlDropColumn Clone(SqlNodeCloneContext context) =>
+      context.GetOrAdd(this, static (t, c) =>
+        new SqlDropColumn(t.Column));
 
     // Constructors
 

Orm/Xtensive.Orm/Sql/Ddl/Actions/SqlDropConstraint.cs

@@ -12,10 +12,9 @@ public class SqlDropConstraint : SqlCascadableAction
   {
     public Constraint Constraint { get; private set; }
 
-    internal override object Clone(SqlNodeCloneContext context) =>
-      context.NodeMapping.TryGetValue(this, out var clone)
-        ? clone
-        : context.NodeMapping[this] = new SqlDropConstraint(Constraint, Cascade);
+    internal override SqlDropConstraint Clone(SqlNodeCloneContext context) =>
+      context.GetOrAdd(this, static (t, c) =>
+        new SqlDropConstraint(t.Constraint, t.Cascade));
 
     // Constructors
 

Orm/Xtensive.Orm/Sql/Ddl/Actions/SqlDropDefault.cs

@@ -12,10 +12,9 @@ public class SqlDropDefault : SqlAction
   {
     public TableColumn Column { get; private set; }
 
-    internal override object Clone(SqlNodeCloneContext context) =>
-      context.NodeMapping.TryGetValue(this, out var clone)
-        ? clone
-        : context.NodeMapping[this] = new SqlDropDefault(Column);
+    internal override SqlDropDefault Clone(SqlNodeCloneContext context) =>
+      context.GetOrAdd(this, static (t, c) =>
+        new SqlDropDefault(t.Column));
 
     // Constructors
 

Orm/Xtensive.Orm/Sql/Ddl/Actions/SqlRenameColumn.cs

@@ -15,10 +15,9 @@ public class SqlRenameColumn : SqlAction
     public TableColumn Column { get; private set; }
     public string NewName { get; private set; }
 
-    internal override object Clone(SqlNodeCloneContext context) =>
-      context.NodeMapping.TryGetValue(this, out var clone)
-        ? clone
-        : context.NodeMapping[this] = new SqlRenameColumn(Column, NewName);
+    internal override SqlRenameColumn Clone(SqlNodeCloneContext context) =>
+      context.GetOrAdd(this, static (t, c) =>
+        new SqlRenameColumn(t.Column, t.NewName));
 
 
     // Constructors

Orm/Xtensive.Orm/Sql/Ddl/Actions/SqlSetDefault.cs

@@ -14,10 +14,9 @@ public class SqlSetDefault : SqlAction
     public TableColumn Column { get; private set; }
     public SqlExpression DefaultValue { get; private set; }
 
-    internal override object Clone(SqlNodeCloneContext context) =>
-      context.NodeMapping.TryGetValue(this, out var clone)
-        ? clone
-        : context.NodeMapping[this] = new SqlSetDefault((SqlExpression) DefaultValue.Clone(context), Column);
+    internal override SqlSetDefault Clone(SqlNodeCloneContext context) =>
+      context.GetOrAdd(this, static (t, c) =>
+        new SqlSetDefault(t.DefaultValue.Clone(c), t.Column));
 
     internal SqlSetDefault(SqlExpression defaultValue, TableColumn column)
     {