Correct nullable annotation on ICustomTypeDescriptor.GetConverter

src/libraries/System.ComponentModel.TypeConverter/ref/System.ComponentModel.TypeConverter.cs

@@ -289,7 +289,7 @@ protected CustomTypeDescriptor(System.ComponentModel.ICustomTypeDescriptor? pare
         public virtual string? GetClassName() { throw null; }
         public virtual string? GetComponentName() { throw null; }
         [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("Generic TypeConverters may require the generic types to be annotated. For example, NullableConverter requires the underlying type to be DynamicallyAccessedMembers All.")]
-        public virtual System.ComponentModel.TypeConverter GetConverter() { throw null; }
+        public virtual System.ComponentModel.TypeConverter? GetConverter() { throw null; }
         [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("The built-in EventDescriptor implementation uses Reflection which requires unreferenced code.")]
         public virtual System.ComponentModel.EventDescriptor? GetDefaultEvent() { throw null; }
         [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("PropertyDescriptor's PropertyType cannot be statically discovered.")]
@@ -584,7 +584,7 @@ public partial interface ICustomTypeDescriptor
         string? GetClassName();
         string? GetComponentName();
         [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("Generic TypeConverters may require the generic types to be annotated. For example, NullableConverter requires the underlying type to be DynamicallyAccessedMembers All.")]
-        System.ComponentModel.TypeConverter GetConverter();
+        System.ComponentModel.TypeConverter? GetConverter();
         [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("The built-in EventDescriptor implementation uses Reflection which requires unreferenced code.")]
         System.ComponentModel.EventDescriptor? GetDefaultEvent();
         [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("PropertyDescriptor's PropertyType cannot be statically discovered.")]

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/CustomTypeDescriptor.cs

@@ -70,7 +70,7 @@ public virtual AttributeCollection GetAttributes()
         /// descriptor is representing.
         /// </summary>
         [RequiresUnreferencedCode(TypeConverter.RequiresUnreferencedCodeMessage)]
-        public virtual TypeConverter GetConverter()
+        public virtual TypeConverter? GetConverter()
         {
             if (_parent != null)
             {

src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/ICustomTypeDescriptor.cs

@@ -30,7 +30,7 @@ public interface ICustomTypeDescriptor
         /// Gets a type converter for this object.
         /// </summary>
         [RequiresUnreferencedCode(TypeConverter.RequiresUnreferencedCodeMessage)]
-        TypeConverter GetConverter();
+        TypeConverter? GetConverter();
 
         /// <summary>
         /// Gets the default event for this object.

src/libraries/System.Data.Common/src/System/Data/Common/DataRecordInternal.cs

@@ -318,9 +318,9 @@ AttributeCollection ICustomTypeDescriptor.GetAttributes()
         }
 
         [RequiresUnreferencedCode("Generic TypeConverters may require the generic types to be annotated. For example, NullableConverter requires the underlying type to be DynamicallyAccessedMembers All.")]
-        TypeConverter ICustomTypeDescriptor.GetConverter()
+        TypeConverter? ICustomTypeDescriptor.GetConverter()
         {
-            return null!;
+            return null;
         }
 
         [RequiresUnreferencedCode("The built-in EventDescriptor implementation uses Reflection which requires unreferenced code.")]

src/libraries/System.Data.Common/src/System/Data/Common/DbDataRecord.cs

@@ -77,7 +77,7 @@ protected virtual DbDataReader GetDbDataReader(int i)
         string? ICustomTypeDescriptor.GetComponentName() => null;
 
         [RequiresUnreferencedCode("Generic TypeConverters may require the generic types to be annotated. For example, NullableConverter requires the underlying type to be DynamicallyAccessedMembers All.")]
-        TypeConverter ICustomTypeDescriptor.GetConverter() => null!;
+        TypeConverter? ICustomTypeDescriptor.GetConverter() => null;
 
         [RequiresUnreferencedCode("The built-in EventDescriptor implementation uses Reflection which requires unreferenced code.")]
         EventDescriptor? ICustomTypeDescriptor.GetDefaultEvent() => null;

src/libraries/System.Data.Common/src/System/Data/DataRowView.cs

@@ -234,7 +234,7 @@ public void EndEdit()
         string? ICustomTypeDescriptor.GetComponentName() => null;
 
         [RequiresUnreferencedCode("Generic TypeConverters may require the generic types to be annotated. For example, NullableConverter requires the underlying type to be DynamicallyAccessedMembers All.")]
-        TypeConverter ICustomTypeDescriptor.GetConverter() => null!;
+        TypeConverter? ICustomTypeDescriptor.GetConverter() => null;
 
         [RequiresUnreferencedCode("The built-in EventDescriptor implementation uses Reflection which requires unreferenced code.")]
         EventDescriptor? ICustomTypeDescriptor.GetDefaultEvent() => null;

src/libraries/System.Data.Common/src/System/Data/DataViewManagerListItemTypeDescriptor.cs

@@ -49,7 +49,7 @@ internal DataView GetDataView(DataTable table)
         /// Retrieves the type converter for this object.
         /// </summary>
         [RequiresUnreferencedCode("Generic TypeConverters may require the generic types to be annotated. For example, NullableConverter requires the underlying type to be DynamicallyAccessedMembers All.")]
-        TypeConverter ICustomTypeDescriptor.GetConverter() => null!;
+        TypeConverter? ICustomTypeDescriptor.GetConverter() => null;
 
         /// <summary>
         /// Retrieves the default event.