Do not report unused parameter diagnostic for parameters of MEF importing constructors

src/EditorFeatures/CSharpTest/RemoveUnusedParametersAndValues/RemoveUnusedParametersTests.cs

@@ -941,6 +941,27 @@ void M(int [|p|])
 }}");
         }
 
+        [Theory, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedParameters)]
+        [InlineData("System.Composition", "ImportingConstructorAttribute")]
+        [InlineData("System.ComponentModel.Composition", "ImportingConstructorAttribute")]
+        public async Task Parameter_ConstructorsWithSpecialAttributes(string attributeNamespace, string attributeName)
+        {
+            await TestDiagnosticMissingAsync(
+$@"
+namespace {attributeNamespace}
+{{
+    public class {attributeName} : System.Attribute {{ }}
+}}
+
+class C
+{{
+    [{attributeNamespace}.{attributeName}()]
+    public C(int [|p|])
+    {{
+    }}
+}}");
+        }
+
         [ConditionalFact(typeof(IsEnglishLocal)), Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnusedParameters)]
         public async Task Parameter_DiagnosticMessages()
         {

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

@@ -159,6 +159,10 @@ private static IEnumerable<INamedTypeSymbol> GetAttributesForMethodsToIgnore(Com
 
                 // Don't flag obsolete methods.
                 yield return compilation.ObsoleteAttribute();
+
+                // Don't flag MEF import constructors with ImportingConstructor attribute.
+                yield return compilation.SystemCompositionImportingConstructorAttribute();
+                yield return compilation.SystemComponentModelCompositionImportingConstructorAttribute();
             }
 
             private bool IsUnusedParameterCandidate(IParameterSymbol parameter)

src/Workspaces/Core/Portable/Shared/Extensions/ICompilationExtensions.cs

@@ -161,5 +161,11 @@ public static INamedTypeSymbol ConditionalAttribute(this Compilation compilation
 
         public static INamedTypeSymbol ObsoleteAttribute(this Compilation compilation)
             => compilation.GetTypeByMetadataName(typeof(ObsoleteAttribute).FullName);
+
+        public static INamedTypeSymbol SystemCompositionImportingConstructorAttribute(this Compilation compilation)
+            => compilation.GetTypeByMetadataName(typeof(System.Composition.ImportingConstructorAttribute).FullName);
+
+        public static INamedTypeSymbol SystemComponentModelCompositionImportingConstructorAttribute(this Compilation compilation)
+            => compilation.GetTypeByMetadataName("System.ComponentModel.Composition.ImportingConstructorAttribute");
     }
 }