From c6f25a4e4200ae70f1aa6911e84b9b325f718dbc Mon Sep 17 00:00:00 2001
From: Max Doerner <maxdoerner@gmx.net>
Date: Sun, 19 Jan 2020 19:11:30 +0100
Subject: [PATCH] Make FunctionReturnValueDiscarded inspections correctly deal
 with output lists

---
 ...ctionReturnValueAlwaysDiscardedInspection.cs |  9 ++++++++-
 .../FunctionReturnValueDiscardedInspection.cs   |  4 +++-
 ...ReturnValueAlwaysDiscardedInspectionTests.cs | 17 +++++++++++++++++
 ...nctionReturnValueDiscardedInspectionTests.cs | 17 +++++++++++++++++
 4 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/Rubberduck.CodeAnalysis/Inspections/Concrete/FunctionReturnValueAlwaysDiscardedInspection.cs b/Rubberduck.CodeAnalysis/Inspections/Concrete/FunctionReturnValueAlwaysDiscardedInspection.cs
index b3bfa0cbdc..a3c3970cc0 100644
--- a/Rubberduck.CodeAnalysis/Inspections/Concrete/FunctionReturnValueAlwaysDiscardedInspection.cs
+++ b/Rubberduck.CodeAnalysis/Inspections/Concrete/FunctionReturnValueAlwaysDiscardedInspection.cs
@@ -144,7 +144,14 @@ private static bool IsCalledAsProcedure(ParserRuleContext context)
                 ? methodCall
                 : context;
             var memberAccessParent = ownFunctionCallExpression.GetAncestor<VBAParser.MemberAccessExprContext>();
-            return memberAccessParent == null;
+            if (memberAccessParent != null)
+            {
+                return false;
+            }
+
+            //If we are in an output list, the value is used somewhere in defining the argument.
+            var outputListParent = context.GetAncestor<VBAParser.OutputListContext>();
+            return outputListParent == null;
         }
 
         protected override string ResultDescription(Declaration declaration)
diff --git a/Rubberduck.CodeAnalysis/Inspections/Concrete/FunctionReturnValueDiscardedInspection.cs b/Rubberduck.CodeAnalysis/Inspections/Concrete/FunctionReturnValueDiscardedInspection.cs
index e4c91a4bcc..96855023a4 100644
--- a/Rubberduck.CodeAnalysis/Inspections/Concrete/FunctionReturnValueDiscardedInspection.cs
+++ b/Rubberduck.CodeAnalysis/Inspections/Concrete/FunctionReturnValueDiscardedInspection.cs
@@ -82,7 +82,9 @@ private static bool IsCalledAsProcedure(ParserRuleContext context)
                 return false;
             }
 
-            return true;
+            //If we are in an output list, the value is used somewhere in defining the argument.
+            var outputListParent = context.GetAncestor<VBAParser.OutputListContext>();
+            return outputListParent == null;
         }
 
         protected override string ResultDescription(IdentifierReference reference)
diff --git a/RubberduckTests/Inspections/FunctionReturnValueAlwaysDiscardedInspectionTests.cs b/RubberduckTests/Inspections/FunctionReturnValueAlwaysDiscardedInspectionTests.cs
index cfcbb9d92f..63b0ecfeb9 100644
--- a/RubberduckTests/Inspections/FunctionReturnValueAlwaysDiscardedInspectionTests.cs
+++ b/RubberduckTests/Inspections/FunctionReturnValueAlwaysDiscardedInspectionTests.cs
@@ -323,6 +323,23 @@ End Sub
             Assert.AreEqual(0, InspectionResultsForStandardModule(code).Count());
         }
 
+        [Test]
+        [Category("Inspections")]
+        [Category("Unused Value")]
+        public void OutputListFunctionCall_DoesNotReturnResult()
+        {
+            const string code = @"
+Public Function Foo(ByVal bar As String) As Integer
+    Foo = 42
+End Function
+
+Public Sub Baz()
+    Debug.Print Foo(""Test"")
+End Sub
+";
+            Assert.AreEqual(0, InspectionResultsForStandardModule(code).Count());
+        }
+
         [Test]
         [Category("Inspections")]
         [Category("Unused Value")]
diff --git a/RubberduckTests/Inspections/FunctionReturnValueDiscardedInspectionTests.cs b/RubberduckTests/Inspections/FunctionReturnValueDiscardedInspectionTests.cs
index 20a4eae77a..e4add27931 100644
--- a/RubberduckTests/Inspections/FunctionReturnValueDiscardedInspectionTests.cs
+++ b/RubberduckTests/Inspections/FunctionReturnValueDiscardedInspectionTests.cs
@@ -281,6 +281,23 @@ End Sub
             Assert.AreEqual(0, InspectionResultsForStandardModule(code).Count());
         }
 
+        [Test]
+        [Category("Inspections")]
+        [Category("Unused Value")]
+        public void FunctionReturnValueDiscarded_DoesNotReturnResult_OutputListFunctionCall()
+        {
+            const string code = @"
+Public Function Foo(ByVal bar As String) As Integer
+    Foo = 42
+End Function
+
+Public Sub Baz()
+    Debug.Print Foo(""Test"")
+End Sub
+";
+            Assert.AreEqual(0, InspectionResultsForStandardModule(code).Count());
+        }
+
         [Test]
         [Category("Inspections")]
         [Category("Unused Value")]