Do not report invalid conversion from int to void for this code:

void Run(Action<string> a) { }
int M() {
    Run(x => $M()$);
}

ICSharpCode.NRefactory.CSharp/Resolver/ResolveVisitor.cs

@@ -1917,8 +1917,10 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 				Log.WriteLine("Applying return type {0} to explicitly-typed lambda {1}", returnType, this.LambdaExpression);
 				if (isAsync)
 					returnType = parentVisitor.UnpackTask(returnType);
-				for (int i = 0; i < returnExpressions.Count; i++) {
-					visitor.ProcessConversion(returnExpressions[i], returnValues[i], returnType);
+				if (returnType.Kind != TypeKind.Void) {
+					for (int i = 0; i < returnExpressions.Count; i++) {
+						visitor.ProcessConversion(returnExpressions[i], returnValues[i], returnType);
+					}
 				}
 			}
 			
@@ -2203,8 +2205,10 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 				Log.WriteLine("Applying return type {0} to implicitly-typed lambda {1}", returnType, lambda.LambdaExpression);
 				if (lambda.IsAsync)
 					returnType = parentVisitor.UnpackTask(returnType);
-				for (int i = 0; i < returnExpressions.Count; i++) {
-					visitor.ProcessConversion(returnExpressions[i], returnValues[i], returnType);
+				if (returnType.Kind != TypeKind.Void) {
+					for (int i = 0; i < returnExpressions.Count; i++) {
+						visitor.ProcessConversion(returnExpressions[i], returnValues[i], returnType);
+					}
 				}
 				
 				visitor.MergeUndecidedLambdas();

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

@@ -392,6 +392,34 @@ class TestClass {
 			Assert.IsFalse(rr.HasParameterList);
 		}
 		
+		[Test]
+		public void NonVoidMethodInActionLambdaIsValidConversion()
+		{
+			string program = @"using System;
+class TestClass {
+	void Run(Action a) { }
+	int M() {
+		Run(() => $M()$);
+	}
+}";
+			var c = GetConversion(program);
+			Assert.IsTrue(c.IsValid);
+		}
+		
+		[Test]
+		public void NonVoidMethodInImplicitlyTypedActionLambdaIsValidConversion()
+		{
+			string program = @"using System;
+class TestClass {
+	void Run(Action<string> a) { }
+	int M() {
+		Run(x => $M()$);
+	}
+}";
+			var c = GetConversion(program);
+			Assert.IsTrue(c.IsValid);
+		}
+		
 		/* TODO write test for this
 class A
 {

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

@@ -159,7 +159,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			}
 		}
 		
-		protected ResolveResult Resolve(string code)
+		protected Tuple<CSharpAstResolver, AstNode> PrepareResolver(string code)
 		{
 			CompilationUnit cu = new CSharpParser().Parse(new StringReader(code.Replace("$", "")), "code.cs");
 			
@@ -176,16 +176,34 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 			cu.AcceptVisitor(fnv, null);
 			Assert.IsNotNull(fnv.ResultNode, "Did not find DOM node at the specified location");
 			
+			CSharpAstResolver resolver = new CSharpAstResolver(compilation, cu, parsedFile);
+			return Tuple.Create(resolver, fnv.ResultNode);
+		}
+		
+		protected ResolveResult Resolve(string code)
+		{
+			var prep = PrepareResolver(code);
 			Debug.WriteLine(new string('=', 70));
-			Debug.WriteLine("Starting new resolver for " + fnv.ResultNode);
+			Debug.WriteLine("Starting new resolver for " + prep.Item2);
 			
-			CSharpAstResolver resolver = new CSharpAstResolver(compilation, cu, parsedFile);
-			ResolveResult rr = resolver.Resolve(fnv.ResultNode);
+			ResolveResult rr = prep.Item1.Resolve(prep.Item2);
 			Assert.IsNotNull(rr, "ResolveResult is null - did something go wrong while navigating to the target node?");
 			Debug.WriteLine("ResolveResult is " + rr);
 			return rr;
 		}
 		
+		protected Conversion GetConversion(string code)
+		{
+			var prep = PrepareResolver(code);
+			return prep.Item1.GetConversion((Expression)prep.Item2);
+		}
+		
+		protected IType GetExpectedType(string code)
+		{
+			var prep = PrepareResolver(code);
+			return prep.Item1.GetExpectedType((Expression)prep.Item2);
+		}
+		
 		protected T Resolve<T>(string code) where T : ResolveResult
 		{
 			ResolveResult rr = Resolve(code);