Merge pull request #36818 from mavasani/UnusedParameterFixes

Fix couple of false positives in unused parameter analyzer

src/EditorFeatures/CSharpTest/RemoveUnusedParametersAndValues/RemoveUnusedParametersTests.cs

@@ -1305,5 +1305,18 @@ public C(Task<IFoo> [|foo|])
     public void Dispose() => foo.Result.Fooed -= fooed;
 }", options);
         }
+
+        [WorkItem(36817, "https://github.com/dotnet/roslyn/issues/36817")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedParameters)]
+        public async Task ParameterWithoutName_NoDiagnostic()
+        {
+            await TestDiagnosticMissingAsync(
+@"public class C
+{
+    public void M[|(int )|]
+    {
+    }
+}");
+        }
     }
 }

src/EditorFeatures/VisualBasicTest/RemoveUnusedParametersAndValues/RemoveUnusedParametersTests.vb

@@ -95,6 +95,22 @@ End Class")
 $"Class C
     [|Sub M(_0 As Integer, _1 As Char, _3 As C)|]
     End Sub
+End Class")
+        End Function
+
+        <WorkItem(36816, "https://github.com/dotnet/roslyn/issues/36816")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedParameters)>
+        Public Async Function PartialMethodParameter_NoDiagnostic() As Task
+            Await TestDiagnosticMissingAsync(
+$"Class C
+    [|Partial Private Sub M(str As String)|]
+    End Sub
+End Class
+
+Partial Class C
+    Private Sub M(str As String)
+        Dim x = str.ToString()
+    End Sub
 End Class")
         End Function
     End Class

src/Features/Core/Portable/RemoveUnusedParametersAndValues/AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.cs

@@ -57,6 +57,12 @@ private sealed partial class SymbolStartAnalyzer
                 var deserializationConstructorCheck = new DeserializationConstructorCheck(context.Compilation);
                 context.RegisterSymbolStartAction(symbolStartContext =>
                 {
+                    if (HasSyntaxErrors((INamedTypeSymbol)symbolStartContext.Symbol, symbolStartContext.CancellationToken))
+                    {
+                        // Bail out on syntax errors.
+                        return;
+                    }
+
                     // Create a new SymbolStartAnalyzer instance for every named type symbol
                     // to ensure there is no shared state (such as identified unused parameters within the type),
                     // as that would lead to duplicate diagnostics being reported from symbol end action callbacks
@@ -64,6 +70,23 @@ private sealed partial class SymbolStartAnalyzer
                     var symbolAnalyzer = new SymbolStartAnalyzer(analyzer, eventsArgType, attributeSetForMethodsToIgnore, deserializationConstructorCheck);
                     symbolAnalyzer.OnSymbolStart(symbolStartContext);
                 }, SymbolKind.NamedType);
+
+                return;
+
+                // Local functions
+                static bool HasSyntaxErrors(INamedTypeSymbol namedTypeSymbol, CancellationToken cancellationToken)
+                {
+                    foreach (var syntaxRef in namedTypeSymbol.DeclaringSyntaxReferences)
+                    {
+                        var syntax = syntaxRef.GetSyntax(cancellationToken);
+                        if (syntax.GetDiagnostics().Any(d => d.Severity == DiagnosticSeverity.Error))
+                        {
+                            return true;
+                        }
+                    }
+
+                    return false;
+                }
             }
 
             private void OnSymbolStart(SymbolStartAnalysisContext context)
@@ -190,6 +213,7 @@ private bool IsUnusedParameterCandidate(IParameterSymbol parameter)
                     method.IsAbstract ||
                     method.IsVirtual ||
                     method.IsOverride ||
+                    method.PartialImplementationPart != null ||
                     !method.ExplicitOrImplicitInterfaceImplementations().IsEmpty ||
                     method.IsAccessor() ||
                     method.IsAnonymousFunction() ||