IDISP004 when yield return.

Fix #215

Author: JohanLarsson

IDisposableAnalyzers.Test/IDISP004DoNotIgnoreCreatedTests/Valid.Returned.cs

@@ -475,5 +475,26 @@ public class C
 }".AssertReplace("new CompositeDisposable(File.OpenRead(fileName))", expression);
             RoslynAssert.Valid(Analyzer, code);
         }
+
+        [Test]
+        public static void YieldReturnFileOpenRead()
+        {
+            var code = @"
+namespace N
+{
+    using System;
+    using System.Collections.Generic;
+    using System.IO;
+
+    class C
+    {
+        IEnumerable<IDisposable> M()
+        {
+            yield return File.OpenRead(string.Empty);
+        }
+    }
+}";
+            RoslynAssert.Valid(Analyzer, code);
+        }
     }
 }

IDisposableAnalyzers/Helpers/Disposable.Returns.cs

@@ -49,6 +49,8 @@ private static bool Returns(ExpressionSyntax candidate, Recursion recursion)
             {
                 { Parent: ReturnStatementSyntax _ }
                 => true,
+                { Parent: YieldStatementSyntax _ }
+                => true,
                 { Parent: ArrowExpressionClauseSyntax { Parent: { } parent } }
                 => !parent.IsKind(SyntaxKind.ConstructorDeclaration),
                 { Parent: MemberAccessExpressionSyntax { Parent: InvocationExpressionSyntax invocation } }

ValidCode/Returned.cs

@@ -0,0 +1,28 @@
+namespace ValidCode
+{
+    using System;
+    using System.Collections.Generic;
+    using System.IO;
+    using System.Linq;
+
+    class Returned
+    {
+        void Consume()
+        {
+            using var fileOpenReadProperty = this.FileOpenReadProperty;
+            using var fileOpenRead = this.FileOpenRead();
+            using var yieldReturnFileOpenRead = this.YieldReturnFileOpenRead().Single();
+        }
+
+#pragma warning disable IDISP012 // Property should not return created disposable.
+        IDisposable FileOpenReadProperty => File.OpenRead(string.Empty);
+#pragma warning restore IDISP012 // Property should not return created disposable.
+
+        IDisposable FileOpenRead() => File.OpenRead(string.Empty);
+
+        IEnumerable<IDisposable> YieldReturnFileOpenRead()
+        {
+            yield return File.OpenRead(string.Empty);
+        }
+    }
+}