Allow conversion of anonymous method with unreachable endpoint to Func<T>.

ICSharpCode.NRefactory.CSharp/Analysis/ReachabilityAnalysis.cs

@@ -0,0 +1,82 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using ICSharpCode.NRefactory.CSharp.Resolver;
+
+namespace ICSharpCode.NRefactory.CSharp.Analysis
+{
+	/// <summary>
+	/// Statement reachability analysis.
+	/// </summary>
+	public sealed class ReachabilityAnalysis
+	{
+		HashSet<Statement> reachableStatements = new HashSet<Statement>();
+		HashSet<Statement> reachableEndPoints = new HashSet<Statement>();
+		HashSet<ControlFlowNode> visitedNodes = new HashSet<ControlFlowNode>();
+		Stack<ControlFlowNode> stack = new Stack<ControlFlowNode>();
+		
+		private ReachabilityAnalysis() {}
+		
+		public static ReachabilityAnalysis Create(Statement statement, CSharpAstResolver resolver = null, CancellationToken cancellationToken = default(CancellationToken))
+		{
+			var cfgBuilder = new ControlFlowGraphBuilder();
+			var cfg = cfgBuilder.BuildControlFlowGraph(statement, resolver, cancellationToken);
+			return Create(cfg, cancellationToken);
+		}
+		
+		public static ReachabilityAnalysis Create(IList<ControlFlowNode> controlFlowGraph, CancellationToken cancellationToken = default(CancellationToken))
+		{
+			if (controlFlowGraph == null)
+				throw new ArgumentNullException("controlFlowGraph");
+			ReachabilityAnalysis ra = new ReachabilityAnalysis();
+			ra.stack.Push(controlFlowGraph[0]);
+			while (ra.stack.Count > 0) {
+				cancellationToken.ThrowIfCancellationRequested();
+				ra.MarkReachable(ra.stack.Pop());
+			}
+			ra.stack = null;
+			ra.visitedNodes = null;
+			return ra;
+		}
+		
+		void MarkReachable(ControlFlowNode node)
+		{
+			if (node.PreviousStatement != null)
+				reachableEndPoints.Add(node.PreviousStatement);
+			if (node.NextStatement != null)
+				reachableStatements.Add(node.NextStatement);
+			foreach (var edge in node.Outgoing) {
+				if (visitedNodes.Add(edge.To))
+					stack.Push(edge.To);
+			}
+		}
+		
+		public bool IsReachable(Statement statement)
+		{
+			return reachableStatements.Contains(statement);
+		}
+		
+		public bool IsEndpointReachable(Statement statement)
+		{
+			return reachableEndPoints.Contains(statement);
+		}
+	}
+}

ICSharpCode.NRefactory.CSharp/ICSharpCode.NRefactory.CSharp.csproj

@@ -60,6 +60,7 @@
   <ItemGroup>
     <Compile Include="Analysis\ControlFlow.cs" />
     <Compile Include="Analysis\DefiniteAssignmentAnalysis.cs" />
+    <Compile Include="Analysis\ReachabilityAnalysis.cs" />
     <Compile Include="Ast\AstNode.cs" />
     <Compile Include="Ast\AstNodeCollection.cs" />
     <Compile Include="Ast\AstType.cs" />

ICSharpCode.NRefactory.CSharp/Resolver/CSharpAstResolver.cs

@@ -78,6 +78,12 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			this.resolveVisitor = new ResolveVisitor(initialResolverState, parsedFile);
 		}
 		
+		internal CSharpAstResolver(ResolveVisitor resolveVisitor)
+		{
+			this.resolveVisitor = resolveVisitor;
+			this.resolverInitialized = true;
+		}
+		
 		/// <summary>
 		/// Gets the type resolve context for the root resolver.
 		/// </summary>

ICSharpCode.NRefactory.CSharp/Resolver/ResolveVisitor.cs

@@ -22,6 +22,7 @@ using System.Diagnostics;
 using System.Linq;
 using System.Text;
 using System.Threading;
+using ICSharpCode.NRefactory.CSharp.Analysis;
 using ICSharpCode.NRefactory.CSharp.TypeSystem;
 using ICSharpCode.NRefactory.Semantics;
 using ICSharpCode.NRefactory.TypeSystem;
@@ -1759,6 +1760,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			IList<Expression> returnExpressions;
 			IList<ResolveResult> returnValues;
 			bool isValidAsVoidMethod;
+			bool isEndpointUnreachable;
 			bool success;
 			
 			// The actual return type is set when the lambda is applied by the conversion.
@@ -1820,7 +1822,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 						delegate {
 							var oldNavigator = visitor.navigator;
 							visitor.navigator = new ConstantModeResolveVisitorNavigator(ResolveVisitorNavigationMode.Resolve, oldNavigator);
-							visitor.AnalyzeLambda(body, isAsync, out success, out isValidAsVoidMethod, out inferredReturnType, out returnExpressions, out returnValues);
+							visitor.AnalyzeLambda(body, isAsync, out success, out isValidAsVoidMethod, out isEndpointUnreachable, out inferredReturnType, out returnExpressions, out returnValues);
 							visitor.navigator = oldNavigator;
 						});
 					Log.Unindent();
@@ -1836,7 +1838,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			{
 				Log.WriteLine("Testing validity of {0} for return-type {1}...", this, returnType);
 				Log.Indent();
-				bool valid = Analyze() && IsValidLambda(isValidAsVoidMethod, isAsync, returnValues, returnType, conversions);
+				bool valid = Analyze() && IsValidLambda(isValidAsVoidMethod, isEndpointUnreachable, isAsync, returnValues, returnType, conversions);
 				Log.Unindent();
 				Log.WriteLine("{0} is {1} for return-type {2}", this, valid ? "valid" : "invalid", returnType);
 				if (valid) {
@@ -2103,6 +2105,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			IList<Expression> returnExpressions;
 			IList<ResolveResult> returnValues;
 			bool isValidAsVoidMethod;
+			bool isEndpointUnreachable;
 			internal bool success;
 			
 			public LambdaTypeHypothesis(ImplicitlyTypedLambda lambda, IType[] parameterTypes, ResolveVisitor visitor,
@@ -2135,7 +2138,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 					}
 				}
 				
-				visitor.AnalyzeLambda(lambda.BodyExpression, lambda.IsAsync, out success, out isValidAsVoidMethod, out inferredReturnType, out returnExpressions, out returnValues);
+				visitor.AnalyzeLambda(lambda.BodyExpression, lambda.IsAsync, out success, out isValidAsVoidMethod, out isEndpointUnreachable, out inferredReturnType, out returnExpressions, out returnValues);
 				visitor.resolver = oldResolver;
 				Log.Unindent();
 				Log.WriteLine("Finished analyzing " + ToString());
@@ -2153,7 +2156,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			
 			public Conversion IsValid(IType returnType, Conversions conversions)
 			{
-				if (success && IsValidLambda(isValidAsVoidMethod, lambda.IsAsync, returnValues, returnType, conversions)) {
+				if (success && IsValidLambda(isValidAsVoidMethod, isEndpointUnreachable, lambda.IsAsync, returnValues, returnType, conversions)) {
 					return new AnonymousFunctionConversion(returnType, this);
 				} else {
 					return Conversion.None;
@@ -2285,8 +2288,9 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 				return SpecialType.UnknownType;
 		}
 		
-		void AnalyzeLambda(AstNode body, bool isAsync, out bool success, out bool isValidAsVoidMethod, out IType inferredReturnType, out IList<Expression> returnExpressions, out IList<ResolveResult> returnValues)
+		void AnalyzeLambda(AstNode body, bool isAsync, out bool success, out bool isValidAsVoidMethod, out bool isEndpointUnreachable, out IType inferredReturnType, out IList<Expression> returnExpressions, out IList<ResolveResult> returnValues)
 		{
+			isEndpointUnreachable = false;
 			Expression expr = body as Expression;
 			if (expr != null) {
 				isValidAsVoidMethod = ExpressionPermittedAsStatement(expr);
@@ -2314,6 +2318,10 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 					inferredReturnType = ti.GetBestCommonType(returnValues, out tiSuccess);
 					// Failure to infer a return type does not make the lambda invalid,
 					// so we can ignore the 'tiSuccess' value
+					if (isValidAsVoidMethod && returnExpressions.Count == 0 && body is Statement) {
+						var reachabilityAnalysis = ReachabilityAnalysis.Create((Statement)body, new CSharpAstResolver(this), cancellationToken);
+						isEndpointUnreachable = !reachabilityAnalysis.IsEndpointReachable((Statement)body);
+					}
 				}
 			}
 			if (isAsync)
@@ -2344,7 +2352,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 				|| expr is AssignmentExpression;
 		}
 		
-		static bool IsValidLambda(bool isValidAsVoidMethod, bool isAsync, IList<ResolveResult> returnValues, IType returnType, Conversions conversions)
+		static bool IsValidLambda(bool isValidAsVoidMethod, bool isEndpointUnreachable, bool isAsync, IList<ResolveResult> returnValues, IType returnType, Conversions conversions)
 		{
 			if (returnType.Kind == TypeKind.Void) {
 				// Lambdas that are valid statement lambdas or expression lambdas with a statement-expression
@@ -2356,7 +2364,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 				return isValidAsVoidMethod;
 			} else {
 				if (returnValues.Count == 0)
-					return false;
+					return isEndpointUnreachable;
 				if (isAsync) {
 					// async lambdas must return Task<T>
 					if (!(IsTask(returnType) && returnType.TypeParameterCount == 1))

ICSharpCode.NRefactory.Tests/CSharp/Resolver/LambdaTests.cs

@@ -446,6 +446,28 @@ class Test {
 			Assert.IsTrue(c.IsValid);
 		}
 		
+		[Test]
+		public void ThrowingAnonymousMethodIsConvertibleToFunc()
+		{
+			string program = @"using System;
+class Test {
+	Func<string, int> x = $delegate { throw new NotImplementedException(); }$;
+}";
+			var c = GetConversion(program);
+			Assert.IsTrue(c.IsValid);
+		}
+		
+		[Test]
+		public void EmptyAnonymousMethodIsNotConvertibleToFunc()
+		{
+			string program = @"using System;
+class Test {
+	Func<string, int> x = $delegate { }$;
+}";
+			var c = GetConversion(program);
+			Assert.IsFalse(c.IsValid);
+		}
+		
 		[Test]
 		public void RaisePropertyChanged_WithExpressionLambda()
 		{