From 4ecda6703ae1a2edc3ef5270852022491444b088 Mon Sep 17 00:00:00 2001
From: Manish Vasani <mavasani@microsoft.com>
Date: Fri, 17 Jan 2020 13:18:04 -0800
Subject: [PATCH] Handle newly added property sub-pattern operation in
 OperationExtensions.GetValueUsageInfo

Fix #40499
---
 .../RemoveUnusedValueAssignmentTests.cs       | 54 +++++++++++++++++++
 .../Extensions/OperationExtensions.cs         |  8 +++
 2 files changed, 62 insertions(+)

diff --git a/src/EditorFeatures/CSharpTest/RemoveUnusedParametersAndValues/RemoveUnusedValueAssignmentTests.cs b/src/EditorFeatures/CSharpTest/RemoveUnusedParametersAndValues/RemoveUnusedValueAssignmentTests.cs
index b970e67e82e..8bb0ca1e8db 100644
--- a/src/EditorFeatures/CSharpTest/RemoveUnusedParametersAndValues/RemoveUnusedValueAssignmentTests.cs
+++ b/src/EditorFeatures/CSharpTest/RemoveUnusedParametersAndValues/RemoveUnusedValueAssignmentTests.cs
@@ -7415,6 +7415,60 @@ string M(object obj)
 }", new TestParameters(options: PreferUnusedLocal, parseOptions: new CSharpParseOptions(LanguageVersion.CSharp8)));
         }
 
+        [WorkItem(40499, "https://github.com/dotnet/roslyn/issues/40499")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedValues)]
+        public async Task LocalUsedWithPropertySubPattern()
+        {
+            await TestDiagnosticMissingAsync(
+@"class C
+{
+    public object P { get; }
+    void M()
+    {
+        C [|c|] = new C();
+        var x = c is { P : int i };
+    }
+}", new TestParameters(options: PreferDiscard, parseOptions: new CSharpParseOptions(LanguageVersion.CSharp8)));
+        }
+
+        [WorkItem(40499, "https://github.com/dotnet/roslyn/issues/40499")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedValues)]
+        public async Task UnusedLocalDefinedInPropertySubPattern_PreferDiscard()
+        {
+            await TestInRegularAndScriptAsync(
+@"class C
+{
+    public object P { get; }
+    void M(C c)
+    {
+        var x = c is { P : int [|i|] };
+    }
+}",
+@"class C
+{
+    public object P { get; }
+    void M(C c)
+    {
+        var x = c is { P : int _ };
+    }
+}", options: PreferDiscard, parseOptions: new CSharpParseOptions(LanguageVersion.CSharp8));
+        }
+
+        [WorkItem(40499, "https://github.com/dotnet/roslyn/issues/40499")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedValues)]
+        public async Task UnusedLocalDefinedInPropertySubPattern_PreferUnusedLocal()
+        {
+            await TestDiagnosticMissingAsync(
+@"class C
+{
+    public object P { get; }
+    void M(C c)
+    {
+        var x = c is { P : int [|i|] };
+    }
+}", new TestParameters(options: PreferUnusedLocal, parseOptions: new CSharpParseOptions(LanguageVersion.CSharp8)));
+        }
+
         [WorkItem(38640, "https://github.com/dotnet/roslyn/issues/38640")]
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedValues)]
         public async Task DeclarationPatternInSwitchExpressionArm_UnusedLocal_PreferDiscard()
diff --git a/src/Workspaces/Core/Portable/Extensions/OperationExtensions.cs b/src/Workspaces/Core/Portable/Extensions/OperationExtensions.cs
index 3e5adab1a5c..5ad882b2767 100644
--- a/src/Workspaces/Core/Portable/Extensions/OperationExtensions.cs
+++ b/src/Workspaces/Core/Portable/Extensions/OperationExtensions.cs
@@ -91,6 +91,14 @@ public static ValueUsageInfo GetValueUsageInfo(this IOperation operation)
                         //
                         return ValueUsageInfo.Write;
 
+                    case IPropertySubpatternOperation _:
+                        // A declaration pattern within a property sub-pattern is a
+                        // write for the declared local.
+                        // For example, 'x' is defined and assigned the value from 'obj.Property' below:
+                        //      if (obj is { Property : int x })
+                        //
+                        return ValueUsageInfo.Write;
+
                     default:
                         Debug.Fail("Unhandled declaration pattern context");
 
-- 
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