Fix null exception for array types

src/NexusMods.MnemonicDB.SourceGenerator/AnalyzedAttribute.cs

@@ -3,12 +3,12 @@
 
 namespace NexusMods.MnemonicDB.SourceGenerator;
 
 public class AnalyzedAttribute
 {
     public string Name { get; set; } = "";
     public string FieldName { get; set; } = "";
 
     public string ContextualName
     {
         get
         {
@@ -24,11 +24,11 @@
         }
     }
 
     public bool IsReference => Flags.HasFlag(AttributeFlags.Reference);
     public bool IsCollection => Flags.HasFlag(AttributeFlags.Collection);
     public bool IsScalar => Flags.HasFlag(AttributeFlags.Scalar);
     public bool IsIndexed => Markers.Contains("IsIndexed");
     public bool IsOptional => Markers.Contains("IsOptional");
 
     /// <summary>
     /// True if this is a value type.
@@ -50,10 +50,10 @@
     /// </summary>
     public bool IsMarker => Flags.HasFlag(AttributeFlags.Marker);
 
     public AttributeFlags Flags { get; set; }
     public INamedTypeSymbol AttributeType { get; set; } = null!;
-    public INamedTypeSymbol HighLevelType { get; set; } = null!;
-    public INamedTypeSymbol LowLevelType { get; set; } = null!;
+    public ITypeSymbol HighLevelType { get; set; } = null!;
+    public ITypeSymbol LowLevelType { get; set; } = null!;
     public INamedTypeSymbol ReferenceType { get; set; } = null!;
     public HashSet<string> Markers { get; set; } = new();
     public string Comments { get; set; } = "";

src/NexusMods.MnemonicDB.SourceGenerator/ModelAnalyzer.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Microsoft.CodeAnalysis;
@@ -243,8 +244,8 @@ private HashSet<string> GetInitializerData(IFieldSymbol fieldSymbol)
     }
 
     private bool TryGetAttributeTypes(IFieldSymbol fieldSymbol,
-        out INamedTypeSymbol? highLevel,
-        out INamedTypeSymbol? lowLevel,
+        out ITypeSymbol? highLevel,
+        out ITypeSymbol? lowLevel,
         out AttributeFlags flags)
     {
         var type = fieldSymbol.Type;
@@ -267,13 +268,16 @@ private bool TryGetAttributeTypes(IFieldSymbol fieldSymbol,
 
                 if (SymbolEqualityComparer.Default.Equals(type.OriginalDefinition, _attributeTypeSymbol))
                 {
-                    highLevel = (namedTypeSymbol.TypeArguments[0] as INamedTypeSymbol)!;
+                    Debug.Assert(namedTypeSymbol.TypeArguments.Length == 2);
+
+                    highLevel = namedTypeSymbol.TypeArguments[0];
                     if (SymbolEqualityComparer.Default.Equals(highLevel, _entityIdTypeSymbol))
                         flags |= AttributeFlags.Reference;
 
-                    lowLevel = (namedTypeSymbol.TypeArguments[1] as INamedTypeSymbol)!;
+                    lowLevel = namedTypeSymbol.TypeArguments[1];
                     return true;
                 }
+
                 type = namedTypeSymbol.BaseType;
             }
             else