Fixes TypeNameObjectFormatter.Skim

Be sure to consider the format of TypeNameObject when skimming.

Author: DustinCampbell

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TypeNameObject.cs

@@ -74,12 +74,12 @@ public TypeNameObject(int index)
         _stringValue = null;
     }
 
-    public TypeNameObject(string? typeName)
+    public TypeNameObject(string? stringValue)
     {
-        Debug.Assert(typeName is null || !s_typeNameToIndex.ContainsKey(typeName));
+        Debug.Assert(stringValue is null || !s_typeNameToIndex.ContainsKey(stringValue));
 
         _index = null;
-        _stringValue = typeName;
+        _stringValue = stringValue;
     }
 
     public bool IsNull => _index is null && _stringValue is null;

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Serialization/MessagePack/Formatters/TagHelpers/TypeNameObjectFormatter.cs

@@ -57,10 +57,14 @@ public override void Serialize(ref MessagePackWriter writer, TypeNameObject valu
             writer.Write((int)TypeNameKind.Index);
             writer.Write(index);
         }
-        else
+        else if (value.StringValue is string stringValue)
         {
             writer.Write((int)TypeNameKind.String);
-            CachedStringFormatter.Instance.Serialize(ref writer, value.GetTypeName(), options);
+            CachedStringFormatter.Instance.Serialize(ref writer, stringValue, options);
+        }
+        else
+        {
+            Assumed.Unreachable();
         }
     }
 
@@ -73,7 +77,16 @@ public override void Skim(ref MessagePackReader reader, SerializerCachingOptions
 
         reader.ReadArrayHeaderAndVerify(PropertyCount);
 
-        reader.Skip(); // TypeNameKind
-        CachedStringFormatter.Instance.Skim(ref reader, options); // Name
+        var typeNameKind = (TypeNameKind)reader.ReadInt32();
+        switch (typeNameKind)
+        {
+            case TypeNameKind.Index:
+                reader.Skip(); // Index
+                break;
+
+            case TypeNameKind.String:
+                CachedStringFormatter.Instance.Skim(ref reader, options); // StringValue
+                break;
+        }
     }
 }