Add TypeSystemOptions.Uncached.

ICSharpCode.Decompiler.Tests/Helpers/Tester.cs

@@ -395,12 +395,14 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 
 		public static string DecompileCSharp(string assemblyFileName, DecompilerSettings settings = null)
 		{
+			if (settings == null)
+				settings = new DecompilerSettings();
 			using (var file = new FileStream(assemblyFileName, FileMode.Open, FileAccess.Read)) {
 				var module = new PEFile(assemblyFileName, file, PEStreamOptions.PrefetchEntireImage);
 				var resolver = new UniversalAssemblyResolver(assemblyFileName, false,
 					module.Reader.DetectTargetFrameworkId(), PEStreamOptions.PrefetchMetadata);
-				var typeSystem = new DecompilerTypeSystem(module, resolver);
-				CSharpDecompiler decompiler = new CSharpDecompiler(typeSystem, settings ?? new DecompilerSettings());
+				var typeSystem = new DecompilerTypeSystem(module, resolver, settings);
+				CSharpDecompiler decompiler = new CSharpDecompiler(typeSystem, settings);
 				decompiler.AstTransforms.Insert(0, new RemoveEmbeddedAtttributes());
 				decompiler.AstTransforms.Insert(0, new RemoveCompilerAttribute());
 				decompiler.AstTransforms.Add(new EscapeInvalidIdentifiers());

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -225,6 +225,8 @@ namespace ICSharpCode.Decompiler.CSharp
 			this.settings = settings;
 			this.module = typeSystem.MainModule;
 			this.metadata = module.PEFile.Metadata;
+			if (module.TypeSystemOptions.HasFlag(TypeSystemOptions.Uncached))
+				throw new ArgumentException("Cannot use an uncached type system in the decompiler.");
 		}
 
 		#region MemberIsHidden

ICSharpCode.Decompiler/CSharp/WholeProjectDecompiler.cs

@@ -317,7 +317,7 @@ namespace ICSharpCode.Decompiler.CSharp
 						return Path.Combine(dir, file);
 					}
 				}, StringComparer.OrdinalIgnoreCase).ToList();
-			DecompilerTypeSystem ts = new DecompilerTypeSystem(module, AssemblyResolver);
+			DecompilerTypeSystem ts = new DecompilerTypeSystem(module, AssemblyResolver, settings);
 			Parallel.ForEach(
 				files,
 				new ParallelOptions {

ICSharpCode.Decompiler/TypeSystem/DecompilerTypeSystem.cs

@@ -63,6 +63,16 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		/// </summary>
 		OnlyPublicAPI = 8,
 		/// <summary>
+		/// Do not cache accessed entities.
+		/// In a normal type system (without this option), every type or member definition has exactly one ITypeDefinition/IMember
+		/// instance. This instance is kept alive until the whole type system can be garbage-collected.
+		/// When this option is specified, the type system avoids these caches.
+		/// This reduces the memory usage in many cases, but increases the number of allocations.
+		/// Also, some code in the decompiler expects to be able to compare type/member definitions by reference equality,
+		/// and thus will fail with uncached type systems.
+		/// </summary>
+		Uncached = 0x10,
+		/// <summary>
 		/// Default settings: all features enabled.
 		/// </summary>
 		Default = Dynamic | Tuple | ExtensionMethods
@@ -76,12 +86,7 @@ namespace ICSharpCode.Decompiler.TypeSystem
 	/// </remarks>
 	public class DecompilerTypeSystem : SimpleCompilation, IDecompilerTypeSystem
 	{
-		public DecompilerTypeSystem(PEFile mainModule, IAssemblyResolver assemblyResolver)
-			: this(mainModule, assemblyResolver, TypeSystemOptions.Default)
-		{
-		}
-
-		static TypeSystemOptions GetOptions(DecompilerSettings settings)
+		public static TypeSystemOptions GetOptions(DecompilerSettings settings)
 		{
 			var typeSystemOptions = TypeSystemOptions.None;
 			if (settings.Dynamic)
@@ -93,6 +98,11 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			return typeSystemOptions;
 		}
 
+		public DecompilerTypeSystem(PEFile mainModule, IAssemblyResolver assemblyResolver)
+			: this(mainModule, assemblyResolver, TypeSystemOptions.Default)
+		{
+		}
+
 		public DecompilerTypeSystem(PEFile mainModule, IAssemblyResolver assemblyResolver, DecompilerSettings settings)
 			: this(mainModule, assemblyResolver, GetOptions(settings ?? throw new ArgumentNullException(nameof(settings))))
 		{

ICSharpCode.Decompiler/TypeSystem/Implementation/MetadataTypeDefinition.cs

@@ -127,6 +127,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				foreach (TypeDefinitionHandle h in nestedTypeCollection) {
 					nestedTypeList.Add(module.GetDefinition(h));
 				}
+				if ((module.TypeSystemOptions & TypeSystemOptions.Uncached) != 0)
+					return nestedTypeList;
 				return LazyInit.GetOrSet(ref this.nestedTypes, nestedTypeList.ToArray());
 			}
 		}
@@ -138,6 +140,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				if (members != null)
 					return members;
 				members = this.Fields.Concat<IMember>(this.Methods).Concat(this.Properties).Concat(this.Events).ToArray();
+				if ((module.TypeSystemOptions & TypeSystemOptions.Uncached) != 0)
+					return members;
 				return LazyInit.GetOrSet(ref this.members, members);
 			}
 		}
@@ -157,6 +161,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 						fieldList.Add(module.GetDefinition(h));
 					}
 				}
+				if ((module.TypeSystemOptions & TypeSystemOptions.Uncached) != 0)
+					return fieldList;
 				return LazyInit.GetOrSet(ref this.fields, fieldList.ToArray());
 			}
 		}
@@ -178,6 +184,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 						propertyList.Add(module.GetDefinition(h));
 					}
 				}
+				if ((module.TypeSystemOptions & TypeSystemOptions.Uncached) != 0)
+					return propertyList;
 				return LazyInit.GetOrSet(ref this.properties, propertyList.ToArray());
 			}
 		}
@@ -200,6 +208,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 						eventList.Add(module.GetDefinition(h));
 					}
 				}
+				if ((module.TypeSystemOptions & TypeSystemOptions.Uncached) != 0)
+					return eventList;
 				return LazyInit.GetOrSet(ref this.events, eventList.ToArray());
 			}
 		}
@@ -222,6 +232,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				if (this.Kind == TypeKind.Struct || this.Kind == TypeKind.Enum) {
 					methodsList.Add(FakeMethod.CreateDummyConstructor(Compilation, this, IsAbstract ? Accessibility.Protected : Accessibility.Public));
 				}
+				if ((module.TypeSystemOptions & TypeSystemOptions.Uncached) != 0)
+					return methodsList;
 				return LazyInit.GetOrSet(ref this.methods, methodsList.ToArray());
 			}
 		}

ICSharpCode.Decompiler/TypeSystem/MetadataModule.cs

@@ -68,12 +68,14 @@ namespace ICSharpCode.Decompiler.TypeSystem
 			}
 			this.rootNamespace = new MetadataNamespace(this, null, string.Empty, metadata.GetNamespaceDefinitionRoot());
 
-			// create arrays for resolved entities, indexed by row index
-			this.typeDefs = new MetadataTypeDefinition[metadata.TypeDefinitions.Count + 1];
-			this.fieldDefs = new MetadataField[metadata.FieldDefinitions.Count + 1];
-			this.methodDefs = new MetadataMethod[metadata.MethodDefinitions.Count + 1];
-			this.propertyDefs = new MetadataProperty[metadata.PropertyDefinitions.Count + 1];
-			this.eventDefs = new MetadataEvent[metadata.EventDefinitions.Count + 1];
+			if (!options.HasFlag(TypeSystemOptions.Uncached)) {
+				// create arrays for resolved entities, indexed by row index
+				this.typeDefs = new MetadataTypeDefinition[metadata.TypeDefinitions.Count + 1];
+				this.fieldDefs = new MetadataField[metadata.FieldDefinitions.Count + 1];
+				this.methodDefs = new MetadataMethod[metadata.MethodDefinitions.Count + 1];
+				this.propertyDefs = new MetadataProperty[metadata.PropertyDefinitions.Count + 1];
+				this.eventDefs = new MetadataEvent[metadata.EventDefinitions.Count + 1];
+			}
 		}
 
 		internal string GetString(StringHandle name)
@@ -156,14 +158,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		/// </summary>
 		public IEnumerable<ITypeDefinition> TypeDefinitions {
 			get {
-				for (int row = 1; row < typeDefs.Length; row++) {
-					var typeDef = LazyInit.VolatileRead(ref typeDefs[row]);
-					if (typeDef != null) {
-						yield return typeDef;
-					} else {
-						typeDef = new MetadataTypeDefinition(this, MetadataTokens.TypeDefinitionHandle(row));
-						yield return LazyInit.GetOrSet(ref typeDefs[row], typeDef);
-					}
+				foreach (var tdHandle in metadata.TypeDefinitions) {
+					yield return GetDefinition(tdHandle);
 				}
 			}
 		}
@@ -172,6 +168,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		{
 			if (handle.IsNil)
 				return null;
+			if (typeDefs == null)
+				return new MetadataTypeDefinition(this, handle);
 			int row = MetadataTokens.GetRowNumber(handle);
 			if (row >= typeDefs.Length)
 				HandleOutOfRange(handle);
@@ -186,6 +184,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		{
 			if (handle.IsNil)
 				return null;
+			if (fieldDefs == null)
+				return new MetadataField(this, handle);
 			int row = MetadataTokens.GetRowNumber(handle);
 			if (row >= fieldDefs.Length)
 				HandleOutOfRange(handle);
@@ -200,6 +200,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		{
 			if (handle.IsNil)
 				return null;
+			if (methodDefs == null)
+				return new MetadataMethod(this, handle);
 			int row = MetadataTokens.GetRowNumber(handle);
 			Debug.Assert(row != 0);
 			if (row >= methodDefs.Length)
@@ -215,6 +217,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		{
 			if (handle.IsNil)
 				return null;
+			if (propertyDefs == null)
+				return new MetadataProperty(this, handle);
 			int row = MetadataTokens.GetRowNumber(handle);
 			Debug.Assert(row != 0);
 			if (row >= methodDefs.Length)
@@ -230,6 +234,8 @@ namespace ICSharpCode.Decompiler.TypeSystem
 		{
 			if (handle.IsNil)
 				return null;
+			if (eventDefs == null)
+				return new MetadataEvent(this, handle);
 			int row = MetadataTokens.GetRowNumber(handle);
 			Debug.Assert(row != 0);
 			if (row >= methodDefs.Length)

ILSpy/LoadedAssembly.cs

@@ -99,6 +99,9 @@ namespace ICSharpCode.ILSpy
 		/// Gets a type system containing all types from this assembly + primitve types from mscorlib.
 		/// Returns null in case of load errors.
 		/// </summary>
+		/// <remarks>
+		/// This is an uncached type system.
+		/// </remarks>
 		public ICompilation GetTypeSystemOrNull()
 		{
 			if (typeSystem != null)
@@ -106,7 +109,9 @@ namespace ICSharpCode.ILSpy
 			var module = GetPEFileOrNull();
 			if (module == null)
 				return null;
-			return typeSystem = new SimpleCompilation(module, MinimalCorlib.Instance);
+			return typeSystem = new SimpleCompilation(
+				module.WithOptions(TypeSystemOptions.Default | TypeSystemOptions.Uncached),
+				MinimalCorlib.Instance);
 		}
 
 		public AssemblyList AssemblyList => assemblyList;

ILSpy/MainWindow.xaml.cs

@@ -637,7 +637,8 @@ namespace ICSharpCode.ILSpy
 					OpenLink(opCode.Link);
 					break;
 				case ValueTuple<PEFile, System.Reflection.Metadata.EntityHandle> unresolvedEntity:
-					var typeSystem = new DecompilerTypeSystem(unresolvedEntity.Item1, unresolvedEntity.Item1.GetAssemblyResolver());
+					var typeSystem = new DecompilerTypeSystem(unresolvedEntity.Item1, unresolvedEntity.Item1.GetAssemblyResolver(),
+						TypeSystemOptions.Default | TypeSystemOptions.Uncached);
 					reference = typeSystem.MainModule.ResolveEntity(unresolvedEntity.Item2);
 					goto default;
 				default:

ILSpy/TextView/DecompilerTextView.cs

@@ -210,7 +210,7 @@ namespace ICSharpCode.ILSpy.TextView
 			} else if (segment.Reference is IEntity entity) {
 				return CreateTextBlockForEntity(entity);
 			} else if (segment.Reference is ValueTuple<PEFile, System.Reflection.Metadata.EntityHandle> unresolvedEntity) {
-				var typeSystem = new DecompilerTypeSystem(unresolvedEntity.Item1, unresolvedEntity.Item1.GetAssemblyResolver());
+				var typeSystem = new DecompilerTypeSystem(unresolvedEntity.Item1, unresolvedEntity.Item1.GetAssemblyResolver(), TypeSystemOptions.Default | TypeSystemOptions.Uncached);
 				IEntity resolved = typeSystem.MainModule.ResolveEntity(unresolvedEntity.Item2);
 				if (resolved == null)
 					return null;

ILSpy/TreeNodes/BaseTypesEntryNode.cs

@@ -49,7 +49,8 @@ namespace ICSharpCode.ILSpy.TreeNodes
 
 		ITypeDefinition TryResolve(PEFile module, EntityHandle handle, IType type, bool mayRetry = true)
 		{
-			DecompilerTypeSystem typeSystem = new DecompilerTypeSystem(module, module.GetAssemblyResolver());
+			DecompilerTypeSystem typeSystem = new DecompilerTypeSystem(module, module.GetAssemblyResolver(),
+				TypeSystemOptions.Default | TypeSystemOptions.Uncached);
 			var t = typeSystem.MainModule.ResolveEntity(handle) as ITypeDefinition;
 			if (t != null) {
 				showExpander = t.DirectBaseTypes.Any();