Fixed some bugs in DelegateConstruction (closure display-class reversal is still missing)

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -783,15 +783,15 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		TranslatedExpression TranslateFunction(TranslatedExpression objectCreateExpression, TranslatedExpression target, ILFunction function)
 		{
-			var method = typeSystem.Resolve(function.Method) as IMethod;
+			var method = typeSystem.Resolve(function.Method)?.MemberDefinition as IMethod;
 			Debug.Assert(method != null);
-			
+
 			// Create AnonymousMethodExpression and prepare parameters
 			AnonymousMethodExpression ame = new AnonymousMethodExpression();
 			ame.Parameters.AddRange(MakeParameters(method, function));
 			ame.HasParameterList = true;
-			
-			StatementBuilder builder = new StatementBuilder(typeSystem, decompilationContext, method);
+			var context = new SimpleTypeResolveContext(method);
+			StatementBuilder builder = new StatementBuilder(typeSystem.GetSpecializingTypeSystem(context), context, method);
 			var body = builder.ConvertAsBlock(function.Body);
 			
 			bool isLambda = false;
@@ -1274,12 +1274,17 @@ namespace ICSharpCode.Decompiler.CSharp
 		protected internal override TranslatedExpression VisitIfInstruction(IfInstruction inst)
 		{
 			var condition = TranslateCondition(inst.Condition);
-			var targetType = compilation.FindType(inst.ResultType.ToKnownTypeCode());
-			var trueBranch = Translate(inst.TrueInst).ConvertTo(targetType, this);
-			var falseBranch = Translate(inst.FalseInst).ConvertTo(targetType, this);
-			return new ConditionalExpression(condition.Expression, trueBranch.Expression, falseBranch.Expression)
+			var trueBranch = Translate(inst.TrueInst);
+			var falseBranch = Translate(inst.FalseInst);
+			IType targetType;
+			if (!trueBranch.Type.Equals(SpecialType.NullType) && !falseBranch.Type.Equals(SpecialType.NullType)) {
+				targetType = compilation.FindType(inst.ResultType.ToKnownTypeCode());
+			} else {
+				targetType = trueBranch.Type.Equals(SpecialType.NullType) ? falseBranch.Type : trueBranch.Type;
+			}
+			return new ConditionalExpression(condition.Expression, trueBranch.ConvertTo(targetType, this).Expression, falseBranch.ConvertTo(targetType, this).Expression)
 				.WithILInstruction(inst)
-				.WithRR(new ResolveResult(trueBranch.Type));
+				.WithRR(new ResolveResult(targetType));
 		}
 		
 		protected internal override TranslatedExpression VisitAddressOf(AddressOf inst)

ICSharpCode.Decompiler/IL/Transforms/DelegateConstruction.cs

@@ -49,8 +49,12 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 							block.Instructions.RemoveAt(i);
 							continue;
 						}
-						if (CachedDelegateInitializationWithLocal(inst)) {
+						bool hasFieldStore;
+						if (CachedDelegateInitializationWithLocal(inst, out hasFieldStore)) {
 							block.Instructions.RemoveAt(i);
+							if (hasFieldStore) {
+								block.Instructions.RemoveAt(i - 1);
+							}
 							continue;
 						}
 					}
@@ -96,7 +100,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			var targetMethod = ((IInstructionWithMethodOperand)value.Arguments[1]).Method;
 			if (IsAnonymousMethod(decompilationContext.CurrentTypeDefinition, targetMethod)) {
 				var target = value.Arguments[0];
-				var localTypeSystem = context.TypeSystem.GetSpecializingTypeSystem(decompilationContext);
+				var localTypeSystem = context.TypeSystem.GetSpecializingTypeSystem(new SimpleTypeResolveContext(targetMethod));
 				var function = ILFunction.Read(localTypeSystem, targetMethod, context.CancellationToken);
 				
 				var contextPrefix = targetMethod.Name;
@@ -173,9 +177,48 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			return true;
 		}
 
-		bool CachedDelegateInitializationWithLocal(IfInstruction inst)
+		bool CachedDelegateInitializationWithLocal(IfInstruction inst, out bool hasFieldStore)
 		{
-			return false;
+			// [stloc v(ldsfld CachedAnonMethodDelegate)]
+			// if (comp(ldloc v == ldnull) {
+			//     stloc v(DelegateConstruction)
+			//     [stsfld CachedAnonMethodDelegate(v)]
+			// }
+			// ... one usage of v ...
+			// =>
+			// ... one usage of DelegateConstruction ...
+			Block trueInst = inst.TrueInst as Block;
+			var condition = inst.Condition as Comp;
+			hasFieldStore = false;
+			if (condition == null || trueInst == null || (trueInst.Instructions.Count != 1 && trueInst.Instructions.Count != 2) || !inst.FalseInst.MatchNop())
+				return false;
+			ILVariable v;
+			ILInstruction value, value2;
+			var storeInst = trueInst.Instructions[0];
+			var optionalFieldStore = trueInst.Instructions.ElementAtOrDefault(1);
+			if (!condition.Left.MatchLdLoc(out v) || !condition.Right.MatchLdNull())
+				return false;
+			if (!storeInst.MatchStLoc(v, out value))
+				return false;
+			if (optionalFieldStore != null) {
+				IField field, field2;
+				if (!optionalFieldStore.MatchStsFld(out value2, out field) || !value2.MatchLdLoc(v) || !field.IsCompilerGeneratedOrIsInCompilerGeneratedClass())
+					return false;
+				var storeBeforeIf = inst.Parent.Children.ElementAtOrDefault(inst.ChildIndex - 1) as StLoc;
+				if (storeBeforeIf == null || storeBeforeIf.Variable != v || !storeBeforeIf.Value.MatchLdsFld(out field2) || !field.Equals(field2))
+					return false;
+				hasFieldStore = true;
+			}
+			if (!IsDelegateConstruction(value as NewObj, true))
+				return false;
+			var nextInstruction = inst.Parent.Children.ElementAtOrDefault(inst.ChildIndex + 1);
+			if (nextInstruction == null)
+				return false;
+			var usages = nextInstruction.Descendants.OfType<LdLoc>().Where(i => i.Variable == v).ToArray();
+			if (usages.Length != 1)
+				return false;
+			usages[0].ReplaceWith(value);
+			return true;
 		}
 	}
 }

ICSharpCode.Decompiler/NRExtensions.cs

@@ -33,7 +33,8 @@ namespace ICSharpCode.Decompiler
 			IMethod method = decompilationContext.CurrentMember as IMethod;
 			if (method != null)
 				methodTypeParameters = method.TypeArguments;
-			
+			if (typeSystem is SpecializingDecompilerTypeSystem)
+				typeSystem = ((SpecializingDecompilerTypeSystem)typeSystem).Context;
 			if ((classTypeParameters != null && classTypeParameters.Count > 0) || (methodTypeParameters != null && methodTypeParameters.Count > 0))
 				return new SpecializingDecompilerTypeSystem(typeSystem, new TypeParameterSubstitution(classTypeParameters, methodTypeParameters));
 			else

ICSharpCode.Decompiler/TypeSystem/SpecializingDecompilerTypeSystem.cs

@@ -38,6 +38,10 @@ namespace ICSharpCode.Decompiler
 			this.context = context;
 			this.substitution = substitution;
 		}
+
+		internal IDecompilerTypeSystem Context {
+			get { return context; }
+		}
 		
 		public ICompilation Compilation {
 			get { return context.Compilation; }