some more nullables

src/Serilog/Context/LogContextEnricher.cs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
 using Serilog.Core;
 using Serilog.Events;
 

src/Serilog/Core/Filters/DelegateFilter.cs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
 using System;
 using Serilog.Events;
 

src/Serilog/Core/IDestructuringPolicy.cs

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
+using System.Diagnostics.CodeAnalysis;
 using Serilog.Events;
 
 namespace Serilog.Core
@@ -29,6 +31,6 @@ public interface IDestructuringPolicy
         /// <param name="propertyValueFactory">Recursively apply policies to destructure additional values.</param>
         /// <param name="result">The destructured value, or null.</param>
         /// <returns>True if the value could be destructured under this policy.</returns>
-        bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, out LogEventPropertyValue result);
+        bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, [NotNullWhen(true)] out LogEventPropertyValue? result);
     }
 }

src/Serilog/Core/Pipeline/MessageTemplateCache.cs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
 using System;
 using Serilog.Events;
 
@@ -52,7 +53,7 @@ public MessageTemplate Parse(string messageTemplate)
 #if HASHTABLE
             // ReSharper disable once InconsistentlySynchronizedField
             // ignored warning because this is by design
-            var result = (MessageTemplate)_templates[messageTemplate];
+            var result = (MessageTemplate?)_templates[messageTemplate];
             if (result != null)
                 return result;
 #else

src/Serilog/Policies/DelegateDestructuringPolicy.cs

@@ -12,15 +12,17 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Serilog.Core;
 using Serilog.Events;
 
 namespace Serilog.Policies
 {
     class DelegateDestructuringPolicy : IDestructuringPolicy
     {
-        public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, out LogEventPropertyValue result)
+        public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, [NotNullWhen(true)] out LogEventPropertyValue? result)
         {
             if (value is Delegate del)
             {

src/Serilog/Policies/ProjectedDestructuringPolicy.cs

@@ -12,7 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Serilog.Core;
 using Serilog.Events;
 
@@ -29,7 +31,7 @@ public ProjectedDestructuringPolicy(Func<Type, bool> canApply, Func<object, obje
             _projection = projection ?? throw new ArgumentNullException(nameof(projection));
         }
 
-        public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, out LogEventPropertyValue result)
+        public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, [NotNullWhen(true)] out LogEventPropertyValue? result)
         {
             if (value == null) throw new ArgumentNullException(nameof(value));
 

src/Serilog/Policies/ReflectionTypesScalarDestructuringPolicy.cs

@@ -12,7 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#nullable enable
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using Serilog.Core;
 using Serilog.Events;
@@ -21,7 +23,7 @@ namespace Serilog.Policies
 {
     class ReflectionTypesScalarDestructuringPolicy : IDestructuringPolicy
     {
-        public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, out LogEventPropertyValue result)
+        public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, [NotNullWhen(true)] out LogEventPropertyValue? result)
         {
             // These types and their subclasses are property-laden and deep;
             // most sinks will convert them to strings.

test/TestDummies/DummyHardCodedStringDestructuringPolicy.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Serilog.Core;
 using Serilog.Events;
 
@@ -13,7 +14,7 @@ public DummyHardCodedStringDestructuringPolicy(string hardCodedString)
         _hardCodedString = hardCodedString ?? throw new ArgumentNullException(nameof(hardCodedString));
     }
 
-    public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, out LogEventPropertyValue result)
+    public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, [NotNullWhen(true)] out LogEventPropertyValue? result)
     {
         result = new ScalarValue(_hardCodedString);
         return true;