CA1805: Fix FP with parameterless ctor on value types

src/NetAnalyzers/Core/Microsoft.CodeQuality.Analyzers/QualityGuidelines/DoNotInitializeUnnecessarily.cs

@@ -42,11 +42,21 @@ public sealed override void Initialize(AnalysisContext context)
             {
                 var init = (IFieldInitializerOperation)context.Operation;
                 IFieldSymbol? field = init.InitializedFields.FirstOrDefault();
-                if (field != null &&
-                    !field.IsConst &&
-                    init.Value != null &&
-                    field.GetAttributes().IsEmpty && // in case of attributes that impact nullability analysis
-                    UsesKnownDefaultValue(init.Value, field.Type))
+                if (field == null
+                    || field.IsConst
+                    || init.Value == null
+                    || !field.GetAttributes().IsEmpty) // in case of attributes that impact nullability analysis
+                {
+                    return;
+                }
+
+                // Do not report on instance members of struct but report on static members.
+                if (field.ContainingType?.TypeKind == TypeKind.Struct && !field.IsStatic)
+                {
+                    return;
+                }
+
+                if (UsesKnownDefaultValue(init.Value, field.Type))
                 {
                     context.ReportDiagnostic(init.CreateDiagnostic(DefaultRule, field.Name));
                 }
@@ -56,10 +66,20 @@ public sealed override void Initialize(AnalysisContext context)
             {
                 var init = (IPropertyInitializerOperation)context.Operation;
                 IPropertySymbol? prop = init.InitializedProperties.FirstOrDefault();
-                if (prop != null &&
-                    init.Value != null &&
-                    prop.GetAttributes().IsEmpty && // in case of attributes that impact nullability analysis
-                    UsesKnownDefaultValue(init.Value, prop.Type))
+                if (prop == null
+                    || init.Value == null
+                    || !prop.GetAttributes().IsEmpty) // in case of attributes that impact nullability analysis
+                {
+                    return;
+                }
+
+                // Do not report on instance members of struct but report on static members.
+                if (prop.ContainingType?.TypeKind == TypeKind.Struct && !prop.IsStatic)
+                {
+                    return;
+                }
+
+                if (UsesKnownDefaultValue(init.Value, prop.Type))
                 {
                     context.ReportDiagnostic(init.CreateDiagnostic(DefaultRule, prop.Name));
                 }
@@ -83,7 +103,7 @@ private bool UsesKnownDefaultValue(IOperation value, ITypeSymbol type)
 
             // If this is default(T) or new ValueType(), it's the default.
             if (value is IDefaultValueOperation ||
-                (type.IsValueType && value is IObjectCreationOperation oco && oco.Arguments.IsEmpty && oco.Initializer is null))
+                (type.IsValueType && value is IObjectCreationOperation oco && oco.Arguments.IsEmpty && oco.Initializer is null && oco.Constructor.IsImplicitlyDeclared))
             {
                 return !IsNullSuppressed(value);
             }

src/NetAnalyzers/UnitTests/Microsoft.CodeQuality.Analyzers/QualityGuidelines/DoNotInitializeUnnecessarilyTests.cs

@@ -2,6 +2,7 @@
 
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Testing;
+using Test.Utilities;
 using Xunit;
 using VerifyCS = Test.Utilities.CSharpCodeFixVerifier<
     Microsoft.CodeQuality.CSharp.Analyzers.QualityGuidelines.CSharpDoNotInitializeUnnecessarilyAnalyzer,
@@ -311,6 +312,167 @@ await TestCSAsync(
                     .WithLocation(3));
         }
 
+        [Fact, WorkItem(5750, "https://github.com/dotnet/roslyn-analyzers/issues/5750")]
+        public async Task ParameterlessValueTypeCtor()
+        {
+            await new VerifyCS.Test
+            {
+                TestCode = @"
+using System;
+
+struct S
+{
+    public static readonly S Value = new();
+    public static readonly TimeSpan Time [|= new()|];
+
+    public S() => throw null;
+}
+
+struct S2
+{
+    private readonly int _i;
+    public S2(int i) => _i = i;
+}
+
+class C
+{
+    private S s1 = new S();
+    private S s2 = new();
+
+    private S2 s3 [|= new S2()|];
+    private S2 s4 [|= new()|];
+}",
+                FixedCode = @"
+using System;
+
+struct S
+{
+    public static readonly S Value = new();
+    public static readonly TimeSpan Time;
+
+    public S() => throw null;
+}
+
+struct S2
+{
+    private readonly int _i;
+    public S2(int i) => _i = i;
+}
+
+class C
+{
+    private S s1 = new S();
+    private S s2 = new();
+
+    private S2 s3;
+    private S2 s4;
+}",
+                LanguageVersion = CodeAnalysis.CSharp.LanguageVersion.Preview,
+            }.RunAsync();
+        }
+
+        [Fact, WorkItem(5887, "https://github.com/dotnet/roslyn-analyzers/issues/5887")]
+        public async Task DoNotReportOnInstanceMembersForStructs()
+        {
+            await new VerifyCS.Test
+            {
+                LanguageVersion = CodeAnalysis.CSharp.LanguageVersion.Preview,
+                TestCode = @"
+public record struct MyRecord1
+{
+    private bool _x = false;
+    public MyRecord1() { }
+    public bool SomeBool { get; set; } = false;
+}
+
+public struct MyStruct1
+{
+    private bool _x = false;
+    public MyStruct1() { }
+    public bool SomeBool { get; set; } = false;
+}
+
+public record struct MyRecord2()
+{
+    private bool _x = false;
+    public bool SomeBool { get; set; } = false;
+}",
+            }.RunAsync();
+        }
+
+        [Fact, WorkItem(5887, "https://github.com/dotnet/roslyn-analyzers/issues/5887")]
+        public async Task ReportOnStaticMembersForStructs()
+        {
+            await new VerifyCS.Test
+            {
+                LanguageVersion = CodeAnalysis.CSharp.LanguageVersion.Preview,
+                TestCode = @"
+public record struct MyRecord
+{
+    private static bool _x [|= false|];
+    public static bool SomeBool { get; set; } [|= false|];
+}
+
+public struct MyStruct
+{
+    private static bool _x [|= false|];
+    public static bool SomeBool { get; set; } [|= false|];
+}
+
+public record struct MyRecord2()
+{
+    private static bool _x [|= false|];
+    public static bool SomeBool { get; set; } [|= false|];
+}
+
+public record struct MyRecord3
+{
+    private static bool _x [|= false|];
+    public MyRecord3() { }
+    public static bool SomeBool { get; set; } [|= false|];
+}
+
+public struct MyStruct3
+{
+    private static bool _x [|= false|];
+    public MyStruct3() { }
+    public static bool SomeBool { get; set; } [|= false|];
+}",
+                FixedCode = @"
+public record struct MyRecord
+{
+    private static bool _x;
+    public static bool SomeBool { get; set; }
+}
+
+public struct MyStruct
+{
+    private static bool _x;
+    public static bool SomeBool { get; set; }
+}
+
+public record struct MyRecord2()
+{
+    private static bool _x;
+    public static bool SomeBool { get; set; }
+}
+
+public record struct MyRecord3
+{
+    private static bool _x;
+    public MyRecord3() { }
+    public static bool SomeBool { get; set; }
+}
+
+public struct MyStruct3
+{
+    private static bool _x;
+    public MyStruct3() { }
+    public static bool SomeBool { get; set; }
+}",
+            }.RunAsync();
+        }
+
         private static async Task TestCSAsync(string source, string corrected, params DiagnosticResult[] diagnosticResults)
         {
             var test = new VerifyCS.Test