Fixup pattern we look for before offering ?.

src/EditorFeatures/CSharpTest/UseNullPropagation/UseNullPropagationTests.cs

@@ -291,6 +291,38 @@ void M(object o1, object o2)
     {
         var v1 = o1?.ToString(o2?.ToString());
     }
+}");
+        }
+
+        [WorkItem(15505, "https://github.com/dotnet/roslyn/issues/15505")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseNullPropagation)]
+        public async Task TestOtherValueIsNotNull1()
+        {
+            await TestMissingAsync(
+@"using System;
+
+class C
+{
+    void M(object o)
+    {
+        var v = [||]o == null ? 0 : o.ToString();
+    }
+}");
+        }
+
+        [WorkItem(15505, "https://github.com/dotnet/roslyn/issues/15505")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseNullPropagation)]
+        public async Task TestOtherValueIsNotNull2()
+        {
+            await TestMissingAsync(
+@"using System;
+
+class C
+{
+    void M(object o)
+    {
+        var v = [||]o != null ? o.ToString() : 0;
+    }
 }");
         }
     }

src/Features/Core/Portable/UseNullPropagation/AbstractUseNullPropagationDiagnosticAnalyzer.cs

@@ -99,6 +99,19 @@ private void AnalyzeSyntax(SyntaxNodeAnalysisContext context)
                 return;
             }
 
+            // Needs to be of the forme:
+            //      x == null ? null : ...    or
+            //      x != null ? ...  : null;
+            if (isEquals && !syntaxFacts.IsNullLiteralExpression(whenTrueNode))
+            {
+                return;
+            }
+
+            if (isNotEquals && !syntaxFacts.IsNullLiteralExpression(whenFalseNode))
+            {
+                return;
+            }
+
             var conditionPartToCheck = conditionRightIsNull ? conditionLeft : conditionRight;
             var whenPartToCheck = isEquals ? whenFalseNode : whenTrueNode;