TypeHelper class code formatting and performance improvements

Author: AlexUstinov

Orm/Xtensive.Orm.Tests.Core/Reflection/TypeHelperTest.cs

@@ -421,11 +421,64 @@ public void IsNumericTest()
         this.GetType(),
       };
 
-      foreach (var numericType in numericTypes)
+      foreach (var numericType in numericTypes) {
         Assert.IsTrue(numericType.IsNumericType());
+      }
 
-      foreach (var nonNumericType in nonNumericTypes)
+      foreach (var nonNumericType in nonNumericTypes) {
         Assert.IsFalse(nonNumericType.IsNumericType());
+      }
+    }
+
+    [Test]
+    public void IsNullableTest()
+    {
+      var nullableTypes = new[] {
+        typeof (Nullable<>),
+        typeof (byte?),
+        typeof (sbyte?),
+        typeof (short?),
+        typeof (ushort?),
+        typeof (int?),
+        typeof (uint?),
+        typeof (long?),
+        typeof (ulong?),
+        typeof (float?),
+        typeof (double?),
+        typeof (decimal?),
+        typeof (Guid?)
+      };
+
+      var nonNullableTypes = new[] {
+        typeof (string),
+        typeof (char),
+        typeof (bool),
+        typeof (DateTime),
+        typeof (TimeSpan),
+        typeof (Guid),
+        typeof (TypeCode),
+        typeof (byte[]),
+        typeof (Key),
+        this.GetType()
+      };
+
+      foreach (var type in nullableTypes) {
+        Assert.IsTrue(type.IsNullable());
+      }
+
+      foreach (var type in nonNullableTypes) {
+        Assert.IsFalse(type.IsNullable());
+      }
+    }
+
+    [Test]
+    public void GenericIsNullableTest()
+    {
+      Assert.IsTrue(TypeHelper.IsNullable<Guid?>());
+      Assert.IsTrue(TypeHelper.IsNullable<int?>());
+
+      Assert.IsFalse(TypeHelper.IsNullable<int>());
+      Assert.IsFalse(TypeHelper.IsNullable<string>());
     }
   }
 }

Orm/Xtensive.Orm/Orm/Upgrade/Internals/DomainModelConverter.cs

@@ -463,9 +463,7 @@ private static void CreateHierarchyForeignKey(TableInfo referencingTable, TableI
 
     private static Type ToNullable(Type type, bool isNullable)
     {
-      return isNullable && type.IsValueType && !type.IsNullable()
-        ? type.ToNullable()
-        : type;
+      return isNullable ? type.ToNullable() : type;
     }
 
     private void ProcessDirectAssociation(TypeInfo ownerType, FieldInfo ownerField, TypeInfo targetType)

Orm/Xtensive.Orm/Orm/Upgrade/Internals/SqlModelConverter.cs

@@ -263,11 +263,10 @@ private StorageTypeInfo ExtractType(TableColumn column)
         return StorageTypeInfo.Undefined;
       }
 
-      if (column.IsNullable 
-        && type.IsValueType 
-        && !type.IsNullable())
+      if (column.IsNullable) {
         type = type.ToNullable();
-        
+      }
+
       return new StorageTypeInfo(type, sqlValueType, column.IsNullable, sqlValueType.Length, sqlValueType.Precision, sqlValueType.Scale);
     }