Enable IDE0059 (#39434)

Contributes to #24055

Author: pranavkm

.editorconfig

@@ -199,6 +199,12 @@ dotnet_diagnostic.CA2200.severity = warning
 # CA2208: Instantiate argument exceptions correctly
 dotnet_diagnostic.CA2208.severity = warning
 
+# CA2245: Do not assign a property to itself
+dotnet_diagnostic.CA2245.severity = warning
+
+# CA2246: Assigning symbol and its member in the same statement
+dotnet_diagnostic.CA2246.severity = warning
+
 # IDE0005: Remove unnecessary usings
 dotnet_diagnostic.IDE0005.severity = warning
 
@@ -224,6 +230,9 @@ dotnet_diagnostic.IDE0051.severity = warning
 # IDE0055: All formatting rules
 dotnet_diagnostic.IDE0055.severity = warning
 
+# IDE0059: Unnecessary assignment to a value
+dotnet_diagnostic.IDE0059.severity = warning
+
 # IDE0073: File header
 dotnet_diagnostic.IDE0073.severity = warning
 file_header_template = Licensed to the .NET Foundation under one or more agreements.\nThe .NET Foundation licenses this file to you under the MIT license.
@@ -274,6 +283,8 @@ dotnet_diagnostic.CA2012.severity = suggestion
 dotnet_diagnostic.IDE0044.severity = suggestion
 # IDE0051: Remove unused private members
 dotnet_diagnostic.IDE0051.severity = suggestion
+# IDE0059: Unnecessary assignment to a value
+dotnet_diagnostic.IDE0059.severity = suggestion
 
 # CA2016: Forward the 'CancellationToken' parameter to methods that take one
 dotnet_diagnostic.CA2016.severity = suggestion

src/Azure/AzureAD/Authentication.AzureADB2C.UI/src/AzureAdB2COpenIDConnectEventHandlers.cs

@@ -40,7 +40,7 @@ public Task OnRedirectToIdentityProvider(RedirectContext context)
 
     private string BuildIssuerAddress(RedirectContext context, string defaultPolicy, string policy)
     {
-        if (!_policyToIssuerAddress.TryGetValue(policy, out var issuerAddress))
+        if (!_policyToIssuerAddress.TryGetValue(policy, out _))
         {
             _policyToIssuerAddress[policy] = context.ProtocolMessage.IssuerAddress.ToLowerInvariant()
                 .Replace($"/{defaultPolicy.ToLowerInvariant()}/", $"/{policy.ToLowerInvariant()}/");

src/Caching/StackExchangeRedis/src/RedisCache.cs

@@ -124,7 +124,7 @@ public void Set(string key, byte[] value, DistributedCacheEntryOptions options)
 
         var absoluteExpiration = GetAbsoluteExpiration(creationTime, options);
 
-        var result = _cache.ScriptEvaluate(_setScript, new RedisKey[] { _instance + key },
+        _cache.ScriptEvaluate(_setScript, new RedisKey[] { _instance + key },
             new RedisValue[]
             {
                         absoluteExpiration?.Ticks ?? NotPresent,
@@ -430,9 +430,9 @@ private void Refresh(string key, DateTimeOffset? absExpr, TimeSpan? sldExpr)
         }
 
         // Note Refresh has no effect if there is just an absolute expiration (or neither).
-        TimeSpan? expr = null;
         if (sldExpr.HasValue)
         {
+            TimeSpan? expr;
             if (absExpr.HasValue)
             {
                 var relExpr = absExpr.Value - DateTimeOffset.Now;
@@ -457,9 +457,9 @@ private void Refresh(string key, DateTimeOffset? absExpr, TimeSpan? sldExpr)
         token.ThrowIfCancellationRequested();
 
         // Note Refresh has no effect if there is just an absolute expiration (or neither).
-        TimeSpan? expr = null;
         if (sldExpr.HasValue)
         {
+            TimeSpan? expr;
             if (absExpr.HasValue)
             {
                 var relExpr = absExpr.Value - DateTimeOffset.Now;

src/Components/WebView/Samples/PhotinoPlatform/src/PhotinoWebViewManager.cs

@@ -49,7 +49,7 @@ public PhotinoWebViewManager(PhotinoWindow window, IServiceProvider provider, Di
         var hasFileExtension = url.LastIndexOf('.') > url.LastIndexOf('/');
 
         if (url.StartsWith(AppBaseUri, StringComparison.Ordinal)
-            && TryGetResponseContent(url, !hasFileExtension, out var statusCode, out var statusMessage, out var content, out var headers))
+            && TryGetResponseContent(url, !hasFileExtension, out _, out _, out var content, out var headers))
         {
             headers.TryGetValue("Content-Type", out contentType);
             return content;

src/DataProtection/Cryptography.Internal/src/SafeHandles/SafeLibraryHandle.cs

@@ -39,8 +39,7 @@ public void ForbidUnload()
         const uint GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS = 0x00000004U;
         const uint GET_MODULE_HANDLE_EX_FLAG_PIN = 0x00000001U;
 
-        IntPtr unused;
-        bool retVal = UnsafeNativeMethods.GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_PIN, this, out unused);
+        bool retVal = UnsafeNativeMethods.GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_PIN, this, out _);
         if (!retVal)
         {
             UnsafeNativeMethods.ThrowExceptionForLastWin32Error();

src/DataProtection/DataProtection/src/ArraySegmentExtensions.cs

@@ -24,6 +24,6 @@ public static void Validate<T>(this ArraySegment<T> arraySegment)
     {
         // Since ArraySegment<T> is a struct, it can be improperly initialized or torn.
         // We call the ctor again to make sure the instance data is valid.
-        var unused = new ArraySegment<T>(arraySegment.Array!, arraySegment.Offset, arraySegment.Count);
+        _ = new ArraySegment<T>(arraySegment.Array!, arraySegment.Offset, arraySegment.Count);
     }
 }

src/DataProtection/DataProtection/src/Cng/DpapiSecretSerializerHelper.cs

@@ -336,7 +336,6 @@ private static string GetRuleFromDpapiNGProtectedPayloadCore(byte* pbData, uint
 
         NCryptDescriptorHandle descriptorHandle;
         LocalAllocHandle unprotectedDataHandle;
-        uint cbUnprotectedData;
         var ntstatus = UnsafeNativeMethods.NCryptUnprotectSecret(
             phDescriptor: out descriptorHandle,
             dwFlags: NCRYPT_UNPROTECT_NO_DECRYPT,
@@ -345,7 +344,7 @@ private static string GetRuleFromDpapiNGProtectedPayloadCore(byte* pbData, uint
             pMemPara: IntPtr.Zero,
             hWnd: IntPtr.Zero,
             ppbData: out unprotectedDataHandle,
-            pcbData: out cbUnprotectedData);
+            pcbData: out _);
         UnsafeNativeMethods.ThrowExceptionForNCryptStatus(ntstatus);
         CryptoUtil.AssertSafeHandleIsValid(descriptorHandle);
 

src/DataProtection/DataProtection/src/KeyManagement/KeyRingBasedDataProtector.cs

@@ -187,11 +187,10 @@ public byte[] Unprotect(byte[] protectedData)
         }
 
         // Argument checking will be done by the callee
-        bool requiresMigration, wasRevoked; // unused
         return DangerousUnprotect(protectedData,
             ignoreRevocationErrors: false,
-            requiresMigration: out requiresMigration,
-            wasRevoked: out wasRevoked);
+            requiresMigration: out _,
+            wasRevoked: out _);
     }
 
     private byte[] UnprotectCore(byte[] protectedData, bool allowOperationsOnRevokedKeys, out UnprotectStatus status)

src/DataProtection/DataProtection/src/KeyManagement/XmlKeyManager.cs

@@ -489,7 +489,7 @@ void IInternalXmlKeyManager.RevokeSingleKey(Guid keyId, DateTimeOffset revocatio
 
     internal KeyValuePair<IXmlRepository, IXmlEncryptor?> GetFallbackKeyRepositoryEncryptorPair()
     {
-        IXmlRepository? repository = null;
+        IXmlRepository? repository;
         IXmlEncryptor? encryptor = null;
 
         // If we're running in Azure Web Sites, the key repository goes in the %HOME% directory.

src/DataProtection/Extensions/src/TimeLimitedDataProtector.cs

@@ -142,7 +142,6 @@ byte[] IDataProtector.Unprotect(byte[] protectedData)
             throw new ArgumentNullException(nameof(protectedData));
         }
 
-        DateTimeOffset expiration; // unused
-        return Unprotect(protectedData, out expiration);
+        return Unprotect(protectedData, out _);
     }
 }

src/Features/JsonPatch/src/Internal/ListAdapter.cs

@@ -63,7 +63,7 @@ public virtual bool TryGet(
     {
         var list = (IList)target;
 
-        if (!TryGetListTypeArgument(list, out var typeArgument, out errorMessage))
+        if (!TryGetListTypeArgument(list, out _, out errorMessage))
         {
             value = null;
             return false;
@@ -96,7 +96,7 @@ public virtual bool TryRemove(
     {
         var list = (IList)target;
 
-        if (!TryGetListTypeArgument(list, out var typeArgument, out errorMessage))
+        if (!TryGetListTypeArgument(list, out _, out errorMessage))
         {
             return false;
         }
@@ -208,8 +208,7 @@ public virtual bool TryTraverse(
             return false;
         }
 
-        var index = -1;
-        if (!int.TryParse(segment, out index))
+        if (!int.TryParse(segment, out var index))
         {
             value = null;
             errorMessage = Resources.FormatInvalidIndexValue(segment);
@@ -307,8 +306,7 @@ protected virtual bool TryGetPositionInfo(
             return true;
         }
 
-        var position = -1;
-        if (int.TryParse(segment, out position))
+        if (int.TryParse(segment, out var position))
         {
             if (position >= 0 && position < list.Count)
             {

src/FileProviders/Embedded/src/Manifest/ManifestDirectory.cs

@@ -99,13 +99,13 @@ internal static void ValidateChildrenAndSetParent(ManifestEntry[] children, Mani
     private ManifestEntry[] CopyChildren()
     {
         var list = new List<ManifestEntry>(Children.Count);
-        for (int i = 0; i < Children.Count; i++)
+        for (var i = 0; i < Children.Count; i++)
         {
             var child = Children[i];
             switch (child)
             {
-                case ManifestSinkDirectory s:
-                case ManifestRootDirectory r:
+                case ManifestSinkDirectory:
+                case ManifestRootDirectory:
                     throw new InvalidOperationException("Unexpected manifest node.");
                 case ManifestDirectory d:
                     var grandChildren = d.CopyChildren();

src/Http/Headers/src/BaseHeaderParser.cs

@@ -28,9 +28,8 @@ public sealed override bool TryParseValue(StringSegment value, ref int index, ou
             return SupportsMultipleValues;
         }
 
-        var separatorFound = false;
         var current = HeaderUtilities.GetNextNonEmptyOrWhitespaceIndex(value, index, SupportsMultipleValues,
-            out separatorFound);
+            out var separatorFound);
 
         if (separatorFound && !SupportsMultipleValues)
         {

src/Http/Headers/src/CacheControlHeaderValue.cs

@@ -728,12 +728,11 @@ private static bool TrySetOptionalTokenList(
         // We have a quoted string. Now verify that the string contains a list of valid tokens separated by ','.
         var current = 1; // skip the initial '"' character.
         var maxLength = valueString.Length - 1; // -1 because we don't want to parse the final '"'.
-        var separatorFound = false;
         var originalValueCount = destination == null ? 0 : destination.Count;
         while (current < maxLength)
         {
             current = HeaderUtilities.GetNextNonEmptyOrWhitespaceIndex(valueString, current, true,
-                out separatorFound);
+                out var separatorFound);
 
             if (current == maxLength)
             {

src/Http/Headers/src/ContentDispositionHeaderValue.cs

@@ -435,7 +435,7 @@ private void SetName(StringSegment parameter, StringSegment value)
         }
         else
         {
-            var processedValue = StringSegment.Empty;
+            StringSegment processedValue;
             if (parameter.EndsWith("*", StringComparison.Ordinal))
             {
                 processedValue = Encode5987(value);

src/Http/Headers/src/ContentRangeHeaderValue.cs

@@ -264,10 +264,7 @@ private static int GetContentRangeLength(StringSegment input, int startIndex, ou
 
         // Read range values <from> and <to> in '<unit> <from>-<to>/<length>'
         var fromStartIndex = current;
-        var fromLength = 0;
-        var toStartIndex = 0;
-        var toLength = 0;
-        if (!TryGetRangeLength(input, ref current, out fromLength, out toStartIndex, out toLength))
+        if (!TryGetRangeLength(input, ref current, out var fromLength, out var toStartIndex, out var toLength))
         {
             return 0;
         }
@@ -288,8 +285,7 @@ private static int GetContentRangeLength(StringSegment input, int startIndex, ou
 
         // We may not have a length (e.g. 'bytes 1-2/*'). But if we do, parse the length now.
         var lengthStartIndex = current;
-        var lengthLength = 0;
-        if (!TryGetLengthLength(input, ref current, out lengthLength))
+        if (!TryGetLengthLength(input, ref current, out var lengthLength))
         {
             return 0;
         }

src/Http/Headers/src/EntityTagHeaderValue.cs

@@ -246,8 +246,7 @@ internal static int GetEntityTagLength(StringSegment input, int startIndex, out
             }
 
             var tagStartIndex = current;
-            var tagLength = 0;
-            if (HttpRuleParser.GetQuotedStringLength(input, current, out tagLength) != HttpParseResult.Parsed)
+            if (HttpRuleParser.GetQuotedStringLength(input, current, out var tagLength) != HttpParseResult.Parsed)
             {
                 return 0;
             }

src/Http/Headers/src/HeaderUtilities.cs

@@ -414,8 +414,6 @@ internal static bool TryParseQualityDouble(StringSegment input, int startIndex,
         var inputLength = input.Length;
         var current = startIndex;
         var limit = startIndex + _qualityValueMaxCharCount;
-
-        var intPart = 0;
         var decPart = 0;
         var decPow = 1;
 
@@ -426,6 +424,7 @@ internal static bool TryParseQualityDouble(StringSegment input, int startIndex,
 
         var ch = input[current];
 
+        int intPart;
         if (ch >= '0' && ch <= '1') // Only values between 0 and 1 are accepted, according to RFC
         {
             intPart = ch - '0';

src/Http/Headers/src/MediaTypeHeaderValue.cs

@@ -579,7 +579,7 @@ private static int GetMediaTypeLength(StringSegment input, int startIndex, out M
 
         var current = startIndex + mediaTypeLength;
         current = current + HttpRuleParser.GetWhitespaceLength(input, current);
-        MediaTypeHeaderValue? mediaTypeHeader = null;
+        MediaTypeHeaderValue? mediaTypeHeader;
 
         // If we're not done and we have a parameter delimiter, then we have a list of parameters.
         if ((current < input.Length) && (input[current] == ';'))

src/Http/Headers/src/RangeItemHeaderValue.cs

@@ -115,7 +115,7 @@ internal static int GetRangeItemListLength(
         }
 
         // Empty segments are allowed, so skip all delimiter-only segments (e.g. ", ,").
-        var current = HeaderUtilities.GetNextNonEmptyOrWhitespaceIndex(input, startIndex, true, out var separatorFound);
+        var current = HeaderUtilities.GetNextNonEmptyOrWhitespaceIndex(input, startIndex, true, separatorFound: out _);
         // It's OK if we didn't find leading separator characters. Ignore 'separatorFound'.
 
         if (current == input.Length)
@@ -135,7 +135,7 @@ internal static int GetRangeItemListLength(
             rangeCollection!.Add(range!);
 
             current = current + rangeLength;
-            current = HeaderUtilities.GetNextNonEmptyOrWhitespaceIndex(input, current, true, out separatorFound);
+            current = HeaderUtilities.GetNextNonEmptyOrWhitespaceIndex(input, current, true, out var separatorFound);
 
             // If the string is not consumed, we must have a delimiter, otherwise the string is not a valid
             // range list.

src/Http/Http.Abstractions/src/HostString.cs

@@ -80,7 +80,7 @@ public string Host
     {
         get
         {
-            GetParts(_value, out var host, out var port);
+            GetParts(_value, out var host, out _);
 
             return host.ToString();
         }
@@ -94,7 +94,7 @@ public int? Port
     {
         get
         {
-            GetParts(_value, out var host, out var port);
+            GetParts(_value, out _, out var port);
 
             if (!StringSegment.IsNullOrEmpty(port)
                 && int.TryParse(port.AsSpan(), NumberStyles.None, CultureInfo.InvariantCulture, out var p))

src/Http/Owin/src/OwinEnvironment.cs

@@ -152,16 +152,14 @@ void IDictionary<string, object>.Add(string key, object value)
 
     bool IDictionary<string, object>.ContainsKey(string key)
     {
-        object value;
-        return ((IDictionary<string, object>)this).TryGetValue(key, out value);
+        return ((IDictionary<string, object>)this).TryGetValue(key, out _);
     }
 
     ICollection<string> IDictionary<string, object>.Keys
     {
         get
         {
-            object value;
-            return _entries.Where(pair => pair.Value.TryGet(_context, out value))
+            return _entries.Where(pair => pair.Value.TryGet(_context, out _))
                 .Select(pair => pair.Key).Concat(_context.Items.Keys.Select(key => Convert.ToString(key, CultureInfo.InvariantCulture))).ToList();
         }
     }

src/Http/Owin/src/OwinFeatureCollection.cs

@@ -304,8 +304,7 @@ bool IHttpWebSocketFeature.IsWebSocketRequest
     {
         get
         {
-            object obj;
-            return Environment.TryGetValue(OwinConstants.WebSocket.AcceptAlt, out obj);
+            return Environment.TryGetValue(OwinConstants.WebSocket.AcceptAlt, out _);
         }
     }
 

src/Http/Routing/src/Constraints/OptionalRouteConstraint.cs

@@ -47,7 +47,7 @@ public bool Match(
             throw new ArgumentNullException(nameof(values));
         }
 
-        if (values.TryGetValue(routeKey, out var value))
+        if (values.TryGetValue(routeKey, out _))
         {
             return InnerConstraint.Match(httpContext,
                                          route,

src/Http/Routing/src/Matching/DfaMatcherBuilder.cs

@@ -447,9 +447,8 @@ private void AddRequiredLiteralValue(RouteEndpoint endpoint, List<DfaNode> nextP
 
     private static void AddLiteralNode(bool includeLabel, List<DfaNode> nextParents, DfaNode parent, string literal)
     {
-        DfaNode next = null;
         if (parent.Literals == null ||
-            !parent.Literals.TryGetValue(literal, out next))
+            !parent.Literals.TryGetValue(literal, out var next))
         {
             next = new DfaNode()
             {

src/Http/Routing/src/Matching/HttpMethodMatcherPolicy.cs

@@ -291,11 +291,11 @@ public IReadOnlyList<PolicyNodeEdge> GetEdges(IReadOnlyList<Endpoint> endpoints)
         // We don't bother returning a 405 when the CORS preflight method doesn't exist.
         // The developer calling the API will see it as a CORS error, which is fine because
         // there isn't an endpoint to check for a CORS policy.
-        if (!edges.TryGetValue(new EdgeKey(AnyMethod, false), out var matches))
+        if (!edges.TryGetValue(new EdgeKey(AnyMethod, false), out _))
         {
             // Methods sorted for testability.
             var endpoint = CreateRejectionEndpoint(allHttpMethods);
-            matches = new List<Endpoint>() { endpoint, };
+            var matches = new List<Endpoint>() { endpoint, };
             edges[new EdgeKey(AnyMethod, false)] = matches;
         }