Properly remove incompatible entity types with the same name.

src/EFCore/Metadata/Internal/EntityType.cs

@@ -2365,7 +2365,10 @@ public virtual Property AddProperty(
                 if (memberInfo.DeclaringType?.IsAssignableFrom(ClrType) != true)
                 {
                     throw new InvalidOperationException(
-                        CoreStrings.PropertyWrongEntityClrType(
+                        HasSharedClrType
+                        ? CoreStrings.PropertyWrongEntitySharedClrType(
+                            memberInfo.Name, this.DisplayName(), ClrType.ShortDisplayName(), memberInfo.DeclaringType?.ShortDisplayName())
+                        : CoreStrings.PropertyWrongEntityClrType(
                             memberInfo.Name, this.DisplayName(), memberInfo.DeclaringType?.ShortDisplayName()));
                 }
             }

src/EFCore/Metadata/Internal/InternalModelBuilder.cs

@@ -82,13 +82,25 @@ private InternalEntityTypeBuilder Entity(
             EntityType entityType;
             if (type.IsNamed)
             {
-                if (type.Type != null
-                    && (Metadata.FindEntityType(Metadata.GetDisplayName(type.Type)) != null
-                        || Metadata.HasEntityTypeWithDefiningNavigation(type.Type)))
+                if (type.Type != null)
                 {
-                    return configurationSource == ConfigurationSource.Explicit
-                        ? throw new InvalidOperationException(CoreStrings.ClashingNonSharedType(type.Name, type.Type.DisplayName()))
-                        : (InternalEntityTypeBuilder)null;
+                    var nonSharedTypes = Metadata.GetEntityTypes(Metadata.GetDisplayName(type.Type));
+                    foreach (var nonSharedType in nonSharedTypes)
+                    {
+                        if (configurationSource.OverridesStrictly(nonSharedType.GetConfigurationSource()))
+                        {
+                            continue;
+                        }
+
+                        return configurationSource == ConfigurationSource.Explicit
+                            ? throw new InvalidOperationException(CoreStrings.ClashingNonSharedType(type.Name, type.Type.DisplayName()))
+                            : (InternalEntityTypeBuilder)null;
+                    }
+
+                    foreach (var nonSharedType in nonSharedTypes)
+                    {
+                        HasNoEntityType(nonSharedType, configurationSource);
+                    }
                 }
 
                 entityType = Metadata.FindEntityType(type.Name);
@@ -139,16 +151,24 @@ private InternalEntityTypeBuilder Entity(
 
             if (entityType != null)
             {
-                if (type.IsNamed && type.Type != null)
+                if (type.Type == null
+                    || entityType.ClrType == type.Type)
                 {
-                    if (entityType.ClrType != type.Type)
-                    {
-                        throw new InvalidOperationException(CoreStrings.ClashingMismatchedSharedType(type.Name));
-                    }
+                    entityType.UpdateConfigurationSource(configurationSource);
+                    return entityType.Builder;
                 }
 
-                entityType.UpdateConfigurationSource(configurationSource);
-                return entityType.Builder;
+                if (configurationSource.OverridesStrictly(entityType.GetConfigurationSource()))
+                {
+                    HasNoEntityType(entityType, configurationSource);
+                }
+                else
+                {
+                    return configurationSource == ConfigurationSource.Explicit
+                        ? throw new InvalidOperationException(
+                            CoreStrings.ClashingMismatchedSharedType(type.Name, entityType.ClrType?.ShortDisplayName()))
+                        : (InternalEntityTypeBuilder)null;
+                }
             }
 
             Metadata.RemoveIgnored(type.Name);

src/EFCore/Metadata/Internal/Model.cs

@@ -568,7 +568,9 @@ public virtual EntityType FindActualEntityType([NotNull] EntityType entityType)
         /// </summary>
         public virtual Type FindClrType([NotNull] string name)
             => _entityTypes.TryGetValue(name, out var entityType)
-                ? entityType.ClrType
+                ? entityType.HasSharedClrType
+                    ? null
+                    : entityType.ClrType
                 : (_entityTypesWithDefiningNavigation.TryGetValue(name, out var entityTypesWithSameType)
                     ? entityTypesWithSameType.FirstOrDefault()?.ClrType
                     : null);

src/EFCore/Properties/CoreStrings.resx

@@ -652,7 +652,7 @@
     <value>The entity type '{entityType}' cannot inherit from '{baseEntityType}' because '{clrType}' is not a descendant of '{baseClrType}'.</value>
   </data>
   <data name="PropertyWrongEntityClrType" xml:space="preserve">
-    <value>CLR property '{property}' cannot be added to entity type '{entityType}' because it is declared on the CLR type '{clrType}'.</value>
+    <value>The CLR property '{property}' cannot be added to entity type '{entityType}' because it is declared on the CLR type '{clrType}'.</value>
   </data>
   <data name="InvalidNavigationWithInverseProperty" xml:space="preserve">
     <value>The InversePropertyAttribute on property '{property}' on type '{entityType}' is not valid. The property '{referencedProperty}' is not a valid navigation property on the related type '{referencedEntityType}'. Ensure that the property exists and is a valid reference or collection navigation property.</value>
@@ -1427,7 +1427,7 @@
     <value>The entity type '{entityType}' cannot be on the principal end of the relationship between '{firstNavigationSpecification}' and '{secondNavigationSpecification}'. The principal entity type must have a key.</value>
   </data>
   <data name="ClashingMismatchedSharedType" xml:space="preserve">
-    <value>The shared type entity type '{entityType}' cannot be added to the model because a shared entity type with the same name but different clr type already exists.</value>
+    <value>The shared type entity type '{entityType}' cannot be added to the model because a shared entity type with the same name but different clr type '{otherClrType}' already exists.</value>
   </data>
   <data name="ClashingNonSharedType" xml:space="preserve">
     <value>The shared type entity type '{entityType}' with clr type '{type}' cannot be added to the model because a non shared entity type with the same clr type already exists.</value>
@@ -1498,4 +1498,7 @@
   <data name="ClashingNamedOwnedType" xml:space="preserve">
     <value>There is already an entity type named '{ownedTypeName}'. Use a different name when configuring the ownership '{ownerEntityType}.{navigation}'.</value>
   </data>
+  <data name="PropertyWrongEntitySharedClrType" xml:space="preserve">
+    <value>The CLR property '{property}' cannot be added to entity type '{entityType}'({sharedType}) because it is declared on the CLR type '{clrType}'.</value>
+  </data>
 </root>

test/EFCore.Tests/Metadata/Internal/InternalModelBuilderTest.cs

@@ -31,20 +31,22 @@ public void Entity_returns_same_instance_for_entity_clr_type()
 
             Assert.NotNull(entityBuilder);
             Assert.NotNull(model.FindEntityType(typeof(Customer)));
-            Assert.Same(entityBuilder, modelBuilder.Entity(typeof(Customer).FullName, ConfigurationSource.DataAnnotation));
+            Assert.Same(entityBuilder, modelBuilder.Entity(typeof(Customer).DisplayName(), ConfigurationSource.DataAnnotation));
+            Assert.NotNull(model.FindEntityType(typeof(Customer)).ClrType);
         }
 
         [ConditionalFact]
-        public void Entity_returns_same_instance_for_entity_type_name()
+        public void Entity_creates_new_instance_for_entity_type_name()
         {
             var model = new Model();
             var modelBuilder = CreateModelBuilder(model);
 
-            var entityBuilder = modelBuilder.Entity(typeof(Customer).FullName, ConfigurationSource.DataAnnotation);
+            var entityBuilder = modelBuilder.Entity(typeof(Customer).DisplayName(), ConfigurationSource.DataAnnotation);
 
             Assert.NotNull(entityBuilder);
-            Assert.NotNull(model.FindEntityType(typeof(Customer).FullName));
-            Assert.Same(entityBuilder, modelBuilder.Entity(typeof(Customer), ConfigurationSource.Explicit));
+            Assert.NotNull(model.FindEntityType(typeof(Customer).DisplayName()));
+            Assert.NotSame(entityBuilder, modelBuilder.Entity(typeof(Customer), ConfigurationSource.Explicit));
+            Assert.NotNull(model.FindEntityType(typeof(Customer)).ClrType);
         }
 
         [ConditionalFact]
@@ -469,27 +471,32 @@ public void Can_add_shared_type()
             var model = new Model();
             var modelBuilder = CreateModelBuilder(model);
 
-            var entityBuilder = modelBuilder.Entity(typeof(Customer), ConfigurationSource.Explicit);
             var sharedTypeName = "SpecialDetails";
 
             Assert.NotNull(modelBuilder.SharedTypeEntity(sharedTypeName, typeof(Details), ConfigurationSource.Convention));
 
             Assert.True(model.FindEntityType(sharedTypeName).HasSharedClrType);
 
-            Assert.Equal(
-                CoreStrings.ClashingMismatchedSharedType("SpecialDetails"),
-                Assert.Throws<InvalidOperationException>(() => modelBuilder.SharedTypeEntity(sharedTypeName, typeof(Product), ConfigurationSource.DataAnnotation)).Message);
+            Assert.Null(modelBuilder.SharedTypeEntity(sharedTypeName, typeof(Product), ConfigurationSource.Convention));
 
             Assert.NotNull(modelBuilder.Entity(typeof(Product), ConfigurationSource.DataAnnotation));
 
             Assert.Null(modelBuilder.SharedTypeEntity(typeof(Product).DisplayName(), typeof(Product), ConfigurationSource.DataAnnotation));
 
-            Assert.NotNull(modelBuilder.Entity(typeof(Product), ConfigurationSource.Explicit));
+            Assert.NotNull(modelBuilder.SharedTypeEntity(sharedTypeName, typeof(Product), ConfigurationSource.Explicit));
+
+            Assert.Equal(typeof(Product), model.FindEntityType(sharedTypeName).ClrType);
+
+            Assert.Equal(
+                CoreStrings.ClashingMismatchedSharedType("SpecialDetails", nameof(Product)),
+                Assert.Throws<InvalidOperationException>(() => modelBuilder.SharedTypeEntity(sharedTypeName, typeof(Details), ConfigurationSource.Explicit)).Message);
+
+            Assert.NotNull(modelBuilder.Entity(typeof(Customer), ConfigurationSource.Explicit));
 
             Assert.Equal(
-                CoreStrings.ClashingNonSharedType(typeof(Product).DisplayName(), typeof(Product).DisplayName()),
+                CoreStrings.ClashingNonSharedType(typeof(Customer).DisplayName(), typeof(Customer).DisplayName()),
                 Assert.Throws<InvalidOperationException>(() =>
-                modelBuilder.SharedTypeEntity(typeof(Product).DisplayName(), typeof(Product), ConfigurationSource.Explicit)).Message);
+                modelBuilder.SharedTypeEntity(typeof(Customer).DisplayName(), typeof(Customer), ConfigurationSource.Explicit)).Message);
         }
 
         private static void Cleanup(InternalModelBuilder modelBuilder)