Merge pull request #38987 from mavasani/FixUnusedValueFalsePositive

Fix regression in RemoveUnusedParametersAndValues analyzer

Author: mavasani

src/EditorFeatures/CSharpTest/RemoveUnusedParametersAndValues/RemoveUnusedValueAssignmentTests.cs

@@ -7149,5 +7149,32 @@ bool GetVal(out string val)
     }
 }");
         }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedValues)]
+        public async Task TupleMember_UsedAfterContinueBranch()
+        {
+            await TestDiagnosticMissingAsync(
+@"
+using System;
+using System.Collections.Generic;
+
+public class Test
+{
+    void M(List<(int, int)> list)
+    {
+        foreach (var (x, [|y|]) in list)
+        {
+            if (x != 0)
+            {
+                continue;
+            }
+
+            Console.Write(y);
+        }
+    }
+}");
+        }
+
+
     }
 }

src/Workspaces/Core/Portable/FlowAnalysis/SymbolUsageAnalysis/SymbolUsageAnalysis.DataFlowAnalyzer.cs

@@ -127,13 +127,17 @@ public override (BasicBlockAnalysisData fallThroughSuccessorData, BasicBlockAnal
                 BasicBlockAnalysisData currentAnalysisData,
                 CancellationToken cancellationToken)
             {
+                // Ensure that we use distinct input BasicBlockAnalysisData instances with identical analysis data for both AnalyzeBranch invocations.
+                using var savedCurrentAnalysisData = BasicBlockAnalysisData.GetInstance();
+                savedCurrentAnalysisData.SetAnalysisDataFrom(currentAnalysisData);
+
                 var newCurrentAnalysisData = AnalyzeBranch(basicBlock.FallThroughSuccessor, basicBlock, currentAnalysisData, cancellationToken);
 
                 // Ensure that we use different instances of block analysis data for fall through successor and conditional successor.
                 _analysisData.AdditionalConditionalBranchAnalysisData.SetAnalysisDataFrom(newCurrentAnalysisData);
                 var fallThroughSuccessorData = _analysisData.AdditionalConditionalBranchAnalysisData;
 
-                var conditionalSuccessorData = AnalyzeBranch(basicBlock.ConditionalSuccessor, basicBlock, currentAnalysisData, cancellationToken);
+                var conditionalSuccessorData = AnalyzeBranch(basicBlock.ConditionalSuccessor, basicBlock, savedCurrentAnalysisData, cancellationToken);
 
                 return (fallThroughSuccessorData, conditionalSuccessorData);
             }