Fix nullable formatting

Author: yevhen

src/SharpAssert.Demo/demo.md

@@ -934,8 +934,8 @@ Assert(value == 42);
 **Output:**
 ```
 Assertion failed: value == 42  at /Users/yb/work/oss/SharpAssert/src/SharpAssert.Demo/Demos/11_NullableTypeDemos.cs:13
-  Left:  HasValue: false
-  Right: HasValue: true, Value: 42
+  Left:  null
+  Right: 42
 ```
 
 ---
@@ -952,8 +952,8 @@ Assert(value == 100);
 **Output:**
 ```
 Assertion failed: value == 100  at /Users/yb/work/oss/SharpAssert/src/SharpAssert.Demo/Demos/11_NullableTypeDemos.cs:22
-  Left:  HasValue: true, Value: 42
-  Right: HasValue: true, Value: 100
+  Left:  42
+  Right: 100
 ```
 
 ---
@@ -970,8 +970,8 @@ Assert(value == true);
 **Output:**
 ```
 Assertion failed: value == true  at /Users/yb/work/oss/SharpAssert/src/SharpAssert.Demo/Demos/11_NullableTypeDemos.cs:31
-  Left:  HasValue: true, Value: False
-  Right: HasValue: true, Value: True
+  Left:  False
+  Right: True
 ```
 
 ---
@@ -989,8 +989,8 @@ Assert(value == expected);
 **Output:**
 ```
 Assertion failed: value == expected  at /Users/yb/work/oss/SharpAssert/src/SharpAssert.Demo/Demos/11_NullableTypeDemos.cs:41
-  Left:  HasValue: false
-  Right: HasValue: true, Value: 10/8/2025
+  Left:  null
+  Right: 10/8/2025
 ```
 
 ---
@@ -1026,8 +1026,8 @@ Assert(value == null);
 **Output:**
 ```
 Assertion failed: value == null  at /Users/yb/work/oss/SharpAssert/src/SharpAssert.Demo/Demos/11_NullableTypeDemos.cs:60
-  Left:  HasValue: true, Value: 42
-  Right: HasValue: false
+  Left:  42
+  Right: null
 ```
 
 ---

src/SharpAssert.Runtime/NullableComparisonFormatter.cs

@@ -44,9 +44,7 @@ static string FormatWithType(object? value, Type expressionType)
         if (!IsNullableType(expressionType))
             return FormatActualValue(value);
 
-        return value == null
-            ? "HasValue: false"
-            : $"HasValue: true, Value: {FormatActualValue(value)}";
+        return value == null ? "null" : $"{FormatActualValue(value)}";
     }
 
     static string FormatRuntimeValue(object? value)
@@ -55,22 +53,21 @@ static string FormatRuntimeValue(object? value)
             return "null";
 
         var type = value.GetType();
-        if (IsNullableType(type))
-        {
-            var hasValueProperty = type.GetProperty("HasValue");
-            var valueProperty = type.GetProperty("Value");
-
-            if (hasValueProperty?.GetValue(value) is bool hasValue)
-            {
-                if (!hasValue)
-                    return "HasValue: false";
-
-                var actualValue = valueProperty?.GetValue(value);
-                return $"HasValue: true, Value: {FormatActualValue(actualValue)}";
-            }
-        }
-
-        return FormatActualValue(value);
+        if (!IsNullableType(type))
+            return FormatActualValue(value);
+
+        var hasValueProperty = type.GetProperty("HasValue");
+        var valueProperty = type.GetProperty("Value");
+
+        if (hasValueProperty?.GetValue(value) is not bool hasValue)
+            return FormatActualValue(value);
+
+        if (!hasValue)
+            return "null";
+
+        var actualValue = valueProperty?.GetValue(value);
+        return $"{FormatActualValue(actualValue)}";
+
     }
 
     static bool IsNullableType(Type? type)

src/SharpAssert.Tests/NullableTypeFixture.cs

@@ -132,7 +132,7 @@ public void Should_show_HasValue_information_in_detailed_diagnostics()
         Expression<Func<bool>> expr = () => nullableWithoutValue == nullableWithValue;
 
         AssertExpressionThrows(expr, "nullableWithoutValue == nullableWithValue", "TestFile.cs", 123,
-            "*HasValue: false*HasValue: true, Value: 42*");
+            "*null*42*");
     }
 
     [Test]
@@ -142,6 +142,6 @@ public void Should_handle_null_comparison_edge_cases()
         Expression<Func<bool>> expr = () => nullable == null;
 
         AssertExpressionThrows(expr, "nullable == null", "TestFile.cs", 123,
-            "*HasValue: true, Value: 42*HasValue: false*");
+            "*42*null*");
     }
 }