Merge remote-tracking branch 'upstream/master' into merges/master-to-features/target-typing

docs/compilers/CSharp/Warnversion Warning Waves.md

+# /warnversion warning "waves"
+
+The C# compiler flag `/warnversion` controls optional warnings.
+When we introduce new warnings that can be reported on existing code,
+we do so under an opt-in system so that programmers do not see new warnings
+without taking action to enable them.
+For that purpose, we have introduced the compiler flag "`/warnversion=n`"
+where `n` is a whole number or a decimal number.
+For a warning that was introduced in dotnet version `k`,
+that warning will be produced if the warning version `n` specified when compiling is
+greater than or equal to `k` and a compiler shipped with dotnet version
+`k` or later is used to compile the code.
+
+The default warning version is `0` (produce no optional warnings).
+Our first warning under control of `/warnversion` was introduced in version `5`
+as part of .NET 5.
+If you want the compiler to produce all applicable warnings, you can specify
+`/warnversion=9999`.
+In the project file, the property used to specify the warning version is `AnalysisLevel`.
+
+The table below describes all of the warnings controlled by `/warnversion`.
+
+| Warning ID | warnversion | Description |
+|------------|---------|-------------|
+| CS8073 | 5 | [Expression always true (or false) when comparing a struct to null](https://github.com/dotnet/roslyn/issues/45744) |

src/Analyzers/Core/Analyzers/RemoveUnnecessarySuppressions/AbstractRemoveUnnecessaryPragmaSuppressionsDiagnosticAnalyzer.cs

@@ -190,9 +190,12 @@ protected sealed override void InitializeWorker(AnalysisContext context)
             // Remove entries for unhandled diagnostic ids.
             foreach (var id in unhandledIds)
             {
-                foreach (var (pragma, _) in idToPragmasMap[id])
+                if (idToPragmasMap.TryGetValue(id, out var pragmas))
                 {
-                    pragmasToIsUsedMap.Remove(pragma);
+                    foreach (var (pragma, _) in pragmas)
+                    {
+                        pragmasToIsUsedMap.Remove(pragma);
+                    }
                 }
 
                 if (idToSuppressMessageAttributesMap.TryGetValue(id, out var attributeNodes))

src/Compilers/CSharp/Portable/CSharpCompilationOptions.cs

@@ -42,6 +42,17 @@ public sealed class CSharpCompilationOptions : CompilationOptions, IEquatable<CS
         /// </summary>
         public override NullableContextOptions NullableContextOptions { get; protected set; }
 
+        /// <summary>
+        /// The warning version, which indicates which set of warnings should be produced by the compiler.
+        /// </summary>
+        /// <remarks>
+        /// Most warnings are produced by the compiler unconditionally, but warnings that are controlled by a version
+        /// are only produced when the WarningVersion value is greater than or equal to the warning version
+        /// associated with the warning. Use zero to get none of the versioned warnings, or a large number like 9999
+        /// to get all of the versioned warnings. The first version that enables some warnings is version 5.
+        /// </remarks>
+        public decimal WarningVersion { get; private set; }
+
         // Defaults correspond to the compiler's defaults or indicate that the user did not specify when that is significant.
         // That's significant when one option depends on another's setting. SubsystemVersion depends on Platform and Target.
         public CSharpCompilationOptions(
@@ -71,7 +82,58 @@ public sealed class CSharpCompilationOptions : CompilationOptions, IEquatable<CS
             StrongNameProvider? strongNameProvider = null,
             bool publicSign = false,
             MetadataImportOptions metadataImportOptions = MetadataImportOptions.Public,
-            NullableContextOptions nullableContextOptions = NullableContextOptions.Disable)
+            NullableContextOptions nullableContextOptions = NullableContextOptions.Disable,
+            decimal warningVersion = 0m)
+            : this(outputKind, reportSuppressedDiagnostics, moduleName, mainTypeName, scriptClassName,
+                   usings, optimizationLevel, checkOverflow, allowUnsafe,
+                   cryptoKeyContainer, cryptoKeyFile, cryptoPublicKey, delaySign, platform,
+                   generalDiagnosticOption, warningLevel,
+                   specificDiagnosticOptions, concurrentBuild, deterministic,
+                   currentLocalTime: default,
+                   debugPlusMode: false,
+                   xmlReferenceResolver: xmlReferenceResolver,
+                   sourceReferenceResolver: sourceReferenceResolver,
+                   metadataReferenceResolver: metadataReferenceResolver,
+                   assemblyIdentityComparer: assemblyIdentityComparer,
+                   strongNameProvider: strongNameProvider,
+                   metadataImportOptions: metadataImportOptions,
+                   referencesSupersedeLowerVersions: false,
+                   publicSign: publicSign,
+                   topLevelBinderFlags: BinderFlags.None,
+                   nullableContextOptions: nullableContextOptions,
+                   warningVersion: warningVersion)
+        {
+        }
+
+        // 16.8 BACKCOMPAT OVERLOAD -- DO NOT TOUCH
+        public CSharpCompilationOptions(
+            OutputKind outputKind,
+            bool reportSuppressedDiagnostics,
+            string? moduleName,
+            string? mainTypeName,
+            string? scriptClassName,
+            IEnumerable<string>? usings,
+            OptimizationLevel optimizationLevel,
+            bool checkOverflow,
+            bool allowUnsafe,
+            string? cryptoKeyContainer,
+            string? cryptoKeyFile,
+            ImmutableArray<byte> cryptoPublicKey,
+            bool? delaySign,
+            Platform platform,
+            ReportDiagnostic generalDiagnosticOption,
+            int warningLevel,
+            IEnumerable<KeyValuePair<string, ReportDiagnostic>>? specificDiagnosticOptions,
+            bool concurrentBuild,
+            bool deterministic,
+            XmlReferenceResolver? xmlReferenceResolver,
+            SourceReferenceResolver? sourceReferenceResolver,
+            MetadataReferenceResolver? metadataReferenceResolver,
+            AssemblyIdentityComparer? assemblyIdentityComparer,
+            StrongNameProvider? strongNameProvider,
+            bool publicSign,
+            MetadataImportOptions metadataImportOptions,
+            NullableContextOptions nullableContextOptions)
             : this(outputKind, reportSuppressedDiagnostics, moduleName, mainTypeName, scriptClassName,
                    usings, optimizationLevel, checkOverflow, allowUnsafe,
                    cryptoKeyContainer, cryptoKeyFile, cryptoPublicKey, delaySign, platform,
@@ -211,7 +273,8 @@ public sealed class CSharpCompilationOptions : CompilationOptions, IEquatable<CS
             bool referencesSupersedeLowerVersions,
             bool publicSign,
             BinderFlags topLevelBinderFlags,
-            NullableContextOptions nullableContextOptions)
+            NullableContextOptions nullableContextOptions,
+            decimal warningVersion = 0m)
             : base(outputKind, reportSuppressedDiagnostics, moduleName, mainTypeName, scriptClassName,
                    cryptoKeyContainer, cryptoKeyFile, cryptoPublicKey, delaySign, publicSign, optimizationLevel, checkOverflow,
                    platform, generalDiagnosticOption, warningLevel, specificDiagnosticOptions.ToImmutableDictionaryOrEmpty(),
@@ -223,6 +286,7 @@ public sealed class CSharpCompilationOptions : CompilationOptions, IEquatable<CS
             this.AllowUnsafe = allowUnsafe;
             this.TopLevelBinderFlags = topLevelBinderFlags;
             this.NullableContextOptions = nullableContextOptions;
+            this.WarningVersion = warningVersion;
         }
 
         private CSharpCompilationOptions(CSharpCompilationOptions other) : this(
@@ -256,7 +320,8 @@ public sealed class CSharpCompilationOptions : CompilationOptions, IEquatable<CS
             reportSuppressedDiagnostics: other.ReportSuppressedDiagnostics,
             publicSign: other.PublicSign,
             topLevelBinderFlags: other.TopLevelBinderFlags,
-            nullableContextOptions: other.NullableContextOptions)
+            nullableContextOptions: other.NullableContextOptions,
+            warningVersion: other.WarningVersion)
         {
         }
 
@@ -493,6 +558,16 @@ public CSharpCompilationOptions WithWarningLevel(int warningLevel)
             return new CSharpCompilationOptions(this) { WarningLevel = warningLevel };
         }
 
+        public CSharpCompilationOptions WithWarningVersion(decimal warningVersion)
+        {
+            if (warningVersion == this.WarningVersion)
+            {
+                return this;
+            }
+
+            return new CSharpCompilationOptions(this) { WarningVersion = warningVersion };
+        }
+
         public new CSharpCompilationOptions WithConcurrentBuild(bool concurrentBuild)
         {
             if (concurrentBuild == this.ConcurrentBuild)
@@ -688,6 +763,11 @@ internal override void ValidateOptions(ArrayBuilder<Diagnostic> builder)
                 builder.Add(Diagnostic.Create(MessageProvider.Instance, (int)ErrorCode.ERR_BadCompilationOptionValue, nameof(WarningLevel), WarningLevel));
             }
 
+            if (WarningVersion < 0m)
+            {
+                builder.Add(Diagnostic.Create(MessageProvider.Instance, (int)ErrorCode.ERR_BadCompilationOptionValue, nameof(WarningVersion), WarningVersion));
+            }
+
             if (Usings != null && Usings.Any(u => !u.IsValidClrNamespaceName()))
             {
                 builder.Add(Diagnostic.Create(MessageProvider.Instance, (int)ErrorCode.ERR_BadCompilationOptionValue, nameof(Usings), Usings.Where(u => !u.IsValidClrNamespaceName()).First() ?? "null"));
@@ -722,8 +802,9 @@ public bool Equals(CSharpCompilationOptions? other)
 
             return this.AllowUnsafe == other.AllowUnsafe &&
                    this.TopLevelBinderFlags == other.TopLevelBinderFlags &&
-                   (this.Usings == null ? other.Usings == null : this.Usings.SequenceEqual(other.Usings, StringComparer.Ordinal) &&
-                   this.NullableContextOptions == other.NullableContextOptions);
+                   (this.Usings == null ? other.Usings == null : this.Usings.SequenceEqual(other.Usings, StringComparer.Ordinal)) &&
+                   this.NullableContextOptions == other.NullableContextOptions &&
+                   this.WarningVersion == other.WarningVersion;
         }
 
         public override bool Equals(object? obj)
@@ -736,7 +817,8 @@ public override int GetHashCode()
             return Hash.Combine(base.GetHashCodeHelper(),
                    Hash.Combine(this.AllowUnsafe,
                    Hash.Combine(Hash.CombineValues(this.Usings, StringComparer.Ordinal),
-                   Hash.Combine(TopLevelBinderFlags.GetHashCode(), this.NullableContextOptions.GetHashCode()))));
+                   Hash.Combine(this.WarningVersion.GetHashCode(),
+                   Hash.Combine(TopLevelBinderFlags.GetHashCode(), this.NullableContextOptions.GetHashCode())))));
         }
 
         internal override Diagnostic FilterDiagnostic(Diagnostic diagnostic)

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -3235,6 +3235,9 @@ A catch() block after a catch (System.Exception e) block can catch non-CLS excep
   <data name="ERR_BadWarningLevel" xml:space="preserve">
     <value>Warning level must be in the range 0-4</value>
   </data>
+  <data name="ERR_BadWarningVersion" xml:space="preserve">
+    <value>Warning version must be greater than or equal to '0'.</value>
+  </data>
   <data name="ERR_BadDebugType" xml:space="preserve">
     <value>Invalid option '{0}' for /debug; must be 'portable', 'embedded', 'full' or 'pdbonly'</value>
   </data>
@@ -4617,7 +4620,9 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/CommandLine/CSharpCommandLineParser.cs

@@ -135,6 +135,7 @@ public new CSharpCommandLineArguments Parse(IEnumerable<string> args, string? ba
             bool publicSign = false;
             string? sourceLink = null;
             string? ruleSetPath = null;
+            decimal warningVersion = 0m;
 
             // Process ruleset files first so that diagnostic severity settings specified on the command line via
             // /nowarn and /warnaserror can override diagnostic severity settings specified in the ruleset file.
@@ -905,6 +906,24 @@ public new CSharpCommandLineArguments Parse(IEnumerable<string> args, string? ba
                             }
                             continue;
 
+                        case "warnversion":
+                            value = RemoveQuotesAndSlashes(value);
+                            decimal newWarningVersion;
+                            if (string.IsNullOrEmpty(value) ||
+                                !decimal.TryParse(value, NumberStyles.Integer | NumberStyles.AllowDecimalPoint, CultureInfo.InvariantCulture, out newWarningVersion))
+                            {
+                                AddDiagnostic(diagnostics, ErrorCode.ERR_SwitchNeedsNumber, name);
+                            }
+                            else if (newWarningVersion < 0m)
+                            {
+                                AddDiagnostic(diagnostics, ErrorCode.ERR_BadWarningVersion, name);
+                            }
+                            else
+                            {
+                                warningVersion = newWarningVersion;
+                            }
+                            continue;
+
                         case "nowarn":
                             if (value == null)
                             {
@@ -1419,7 +1438,8 @@ public new CSharpCommandLineArguments Parse(IEnumerable<string> args, string? ba
                 warningLevel: warningLevel,
                 specificDiagnosticOptions: diagnosticOptions,
                 reportSuppressedDiagnostics: reportSuppressedDiagnostics,
-                publicSign: publicSign
+                publicSign: publicSign,
+                warningVersion: warningVersion
             );
 
             if (debugPlus)

src/Compilers/CSharp/Portable/Errors/ErrorCode.cs

@@ -1835,6 +1835,7 @@ internal enum ErrorCode
         ERR_StaticAnonymousFunctionCannotCaptureVariable = 8820,
         ERR_StaticAnonymousFunctionCannotCaptureThis = 8821,
 
+        ERR_BadWarningVersion = 8848,
         ERR_ExpressionTreeContainsWithExpression = 8849,
         ERR_BadRecordDeclaration = 8850,
         ERR_DuplicateRecordConstructor = 8851,

src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs

@@ -8,6 +8,7 @@
 using System.Diagnostics;
 using System.Globalization;
 using System.Reflection;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp
 {
@@ -206,6 +207,35 @@ private static System.Resources.ResourceManager ResourceManager
             }
         }
 
+        /// <summary>
+        /// For each warning that is linked to a warning "wave" (/warnversion), the number of
+        /// the warning wave in which it was introduced.
+        /// </summary>
+        internal static decimal GetWarningVersion(this ErrorCode code)
+        {
+            // *** ATTENTION!  If you are modifying this method, there are things you need to do.
+
+            // If you introduce a new warning "wave" version (i.e. a new return value
+            // possible from this method), please update
+            // CSharpResources.resx to include documentation for the "latest"
+            // warning version in "IDS_CSCHelp" under "-warnversion". Note that
+            // it is our intention that warning wave version numbers correspond
+            // to the dotnet platform with which the compiler is released.
+
+            // If you introduce a new warning under control of the /warnversion flag
+            // (i.e. a new case in the following switch statement), please update
+            // the file "docs\compilers\CSharp\Warnversion Warning Waves.md"
+            // to document it.
+            switch (code)
+            {
+                case ErrorCode.WRN_NubExprIsConstBool2:
+                    return 5m;
+
+                default:
+                    throw ExceptionUtilities.UnexpectedValue(code);
+            }
+        }
+
         internal static int GetWarningLevel(ErrorCode code)
         {
             if (IsInfo(code) || IsHidden(code))

src/Compilers/CSharp/Portable/Lowering/DiagnosticsPass_Warnings.cs

@@ -792,7 +792,7 @@ private void CheckLiftedBinOp(BoundBinaryOperator node)
 
                     string always = node.OperatorKind.Operator() == BinaryOperatorKind.NotEqual ? "true" : "false";
 
-                    if (_compilation.FeatureStrictEnabled || !node.OperatorKind.IsUserDefined())
+                    if (_compilation.FeatureStrictEnabled || !node.OperatorKind.IsUserDefined() || ErrorCode.WRN_NubExprIsConstBool2.GetWarningVersion() <= this._compilation.Options.WarningVersion)
                     {
                         if (node.Right.NullableNeverHasValue() && node.Left.NullableAlwaysHasValue())
                         {

src/Compilers/CSharp/Portable/PublicAPI.Unshipped.txt

+*REMOVED*Microsoft.CodeAnalysis.CSharp.CSharpCompilationOptions.CSharpCompilationOptions(Microsoft.CodeAnalysis.OutputKind outputKind, bool reportSuppressedDiagnostics = false, string moduleName = null, string mainTypeName = null, string scriptClassName = null, System.Collections.Generic.IEnumerable<string> usings = null, Microsoft.CodeAnalysis.OptimizationLevel optimizationLevel = Microsoft.CodeAnalysis.OptimizationLevel.Debug, bool checkOverflow = false, bool allowUnsafe = false, string cryptoKeyContainer = null, string cryptoKeyFile = null, System.Collections.Immutable.ImmutableArray<byte> cryptoPublicKey = default(System.Collections.Immutable.ImmutableArray<byte>), bool? delaySign = null, Microsoft.CodeAnalysis.Platform platform = Microsoft.CodeAnalysis.Platform.AnyCpu, Microsoft.CodeAnalysis.ReportDiagnostic generalDiagnosticOption = Microsoft.CodeAnalysis.ReportDiagnostic.Default, int warningLevel = 4, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, Microsoft.CodeAnalysis.ReportDiagnostic>> specificDiagnosticOptions = null, bool concurrentBuild = true, bool deterministic = false, Microsoft.CodeAnalysis.XmlReferenceResolver xmlReferenceResolver = null, Microsoft.CodeAnalysis.SourceReferenceResolver sourceReferenceResolver = null, Microsoft.CodeAnalysis.MetadataReferenceResolver metadataReferenceResolver = null, Microsoft.CodeAnalysis.AssemblyIdentityComparer assemblyIdentityComparer = null, Microsoft.CodeAnalysis.StrongNameProvider strongNameProvider = null, bool publicSign = false, Microsoft.CodeAnalysis.MetadataImportOptions metadataImportOptions = Microsoft.CodeAnalysis.MetadataImportOptions.Public, Microsoft.CodeAnalysis.NullableContextOptions nullableContextOptions = Microsoft.CodeAnalysis.NullableContextOptions.Disable) -> void
+Microsoft.CodeAnalysis.CSharp.CSharpCompilationOptions.CSharpCompilationOptions(Microsoft.CodeAnalysis.OutputKind outputKind, bool reportSuppressedDiagnostics = false, string moduleName = null, string mainTypeName = null, string scriptClassName = null, System.Collections.Generic.IEnumerable<string> usings = null, Microsoft.CodeAnalysis.OptimizationLevel optimizationLevel = Microsoft.CodeAnalysis.OptimizationLevel.Debug, bool checkOverflow = false, bool allowUnsafe = false, string cryptoKeyContainer = null, string cryptoKeyFile = null, System.Collections.Immutable.ImmutableArray<byte> cryptoPublicKey = default(System.Collections.Immutable.ImmutableArray<byte>), bool? delaySign = null, Microsoft.CodeAnalysis.Platform platform = Microsoft.CodeAnalysis.Platform.AnyCpu, Microsoft.CodeAnalysis.ReportDiagnostic generalDiagnosticOption = Microsoft.CodeAnalysis.ReportDiagnostic.Default, int warningLevel = 4, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, Microsoft.CodeAnalysis.ReportDiagnostic>> specificDiagnosticOptions = null, bool concurrentBuild = true, bool deterministic = false, Microsoft.CodeAnalysis.XmlReferenceResolver xmlReferenceResolver = null, Microsoft.CodeAnalysis.SourceReferenceResolver sourceReferenceResolver = null, Microsoft.CodeAnalysis.MetadataReferenceResolver metadataReferenceResolver = null, Microsoft.CodeAnalysis.AssemblyIdentityComparer assemblyIdentityComparer = null, Microsoft.CodeAnalysis.StrongNameProvider strongNameProvider = null, bool publicSign = false, Microsoft.CodeAnalysis.MetadataImportOptions metadataImportOptions = Microsoft.CodeAnalysis.MetadataImportOptions.Public, Microsoft.CodeAnalysis.NullableContextOptions nullableContextOptions = Microsoft.CodeAnalysis.NullableContextOptions.Disable, decimal warningVersion = 0) -> void
+Microsoft.CodeAnalysis.CSharp.CSharpCompilationOptions.CSharpCompilationOptions(Microsoft.CodeAnalysis.OutputKind outputKind, bool reportSuppressedDiagnostics, string moduleName, string mainTypeName, string scriptClassName, System.Collections.Generic.IEnumerable<string> usings, Microsoft.CodeAnalysis.OptimizationLevel optimizationLevel, bool checkOverflow, bool allowUnsafe, string cryptoKeyContainer, string cryptoKeyFile, System.Collections.Immutable.ImmutableArray<byte> cryptoPublicKey, bool? delaySign, Microsoft.CodeAnalysis.Platform platform, Microsoft.CodeAnalysis.ReportDiagnostic generalDiagnosticOption, int warningLevel, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, Microsoft.CodeAnalysis.ReportDiagnostic>> specificDiagnosticOptions, bool concurrentBuild, bool deterministic, Microsoft.CodeAnalysis.XmlReferenceResolver xmlReferenceResolver, Microsoft.CodeAnalysis.SourceReferenceResolver sourceReferenceResolver, Microsoft.CodeAnalysis.MetadataReferenceResolver metadataReferenceResolver, Microsoft.CodeAnalysis.AssemblyIdentityComparer assemblyIdentityComparer, Microsoft.CodeAnalysis.StrongNameProvider strongNameProvider, bool publicSign, Microsoft.CodeAnalysis.MetadataImportOptions metadataImportOptions, Microsoft.CodeAnalysis.NullableContextOptions nullableContextOptions) -> void
+Microsoft.CodeAnalysis.CSharp.CSharpCompilationOptions.WarningVersion.get -> decimal
+Microsoft.CodeAnalysis.CSharp.CSharpCompilationOptions.WithWarningVersion(decimal warningVersion) -> Microsoft.CodeAnalysis.CSharp.CSharpCompilationOptions
 Microsoft.CodeAnalysis.CSharp.Conversion.IsConditionalExpression.get -> bool
 Microsoft.CodeAnalysis.CSharp.Syntax.AnonymousFunctionExpressionSyntax.AddModifiers(params Microsoft.CodeAnalysis.SyntaxToken[] items) -> Microsoft.CodeAnalysis.CSharp.Syntax.AnonymousFunctionExpressionSyntax
 Microsoft.CodeAnalysis.CSharp.Syntax.AnonymousFunctionExpressionSyntax.WithModifiers(Microsoft.CodeAnalysis.SyntaxTokenList modifiers) -> Microsoft.CodeAnalysis.CSharp.Syntax.AnonymousFunctionExpressionSyntax

src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Chyba syntaxe příkazového řádku: {0} není platná hodnota možnosti {1}. Hodnota musí mít tvar {2}.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Fehler in der Befehlszeilensyntax: "{0}" ist kein gültiger Wert für die Option "{1}". Der Wert muss im Format "{2}" vorliegen.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Error de sintaxis de la línea de comandos: "{0}" no es un valor válido para la opción "{1}". El valor debe tener el formato "{2}".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Erreur de syntaxe de ligne de commande : '{0}' est une valeur non valide pour l'option '{1}'. La valeur doit se présenter sous la forme '{2}'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Errore di sintassi della riga di comando: '{0}' non è un valore valido per l'opzione '{1}'. Il valore deve essere espresso nel formato '{2}'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf

@@ -152,6 +152,11 @@
         <target state="translated">コマンドライン構文エラー: '{0}' は、'{1}' オプションの有効な値ではありません。値は '{2}' の形式にする必要があります。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf

@@ -152,6 +152,11 @@
         <target state="translated">명령줄 구문 오류: '{0}'은(는) '{1}' 옵션에 유효한 값이 아닙니다. 값은 '{2}' 형식이어야 합니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Błąd składni wiersza polecenia: „{0}” nie jest prawidłową wartością dla opcji „{1}”. Wartość musi mieć postać „{2}”.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Erro de sintaxe de linha de comando: '{0}' não é um valor válido para a opção '{1}'. O valor precisa estar no formato '{2}'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Ошибка в синтаксисе командной строки: "{0}" не является допустимым значением для параметра "{1}". Значение должно иметь форму "{2}".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf

@@ -152,6 +152,11 @@
         <target state="translated">Komut satırı söz dizimi hatası: '{0}', '{1}' seçeneği için geçerli bir değer değil. Değer '{2}' biçiminde olmalıdır.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf

@@ -152,6 +152,11 @@
         <target state="translated">命令行语法错误:“{0}”不是“{1}”选项的有效值。值的格式必须为 "{2}"。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf

@@ -152,6 +152,11 @@
         <target state="translated">命令列語法錯誤: '{0}' 對 '{1}' 選項而言不是有效的值。此值的格式必須是 '{2}'。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_BadWarningVersion">
+        <source>Warning version must be greater than or equal to '0'.</source>
+        <target state="new">Warning version must be greater than or equal to '0'.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -954,7 +959,9 @@
 -warnaserror[+|-]             Report all warnings as errors
 -warnaserror[+|-]:&lt;warn list&gt; Report specific warnings as errors
                               (use "nullable" for all nullability warnings)
--warn:&lt;n&gt;                     Set warning level (0-4) (Short form: -w)
+-warnversion:&lt;n&gt;        Enable recently introduced warnings. Default '0'.
+                              To enable warnings introduced through this version, use '5'.
+                              Use '9999' to enable all current and future warning waves.
 -nowarn:&lt;warn list&gt;           Disable specific warning messages
                               (use "nullable" for all nullability warnings)
 -ruleset:&lt;file&gt;               Specify a ruleset file that disables specific

src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs

@@ -5210,6 +5210,49 @@ public void WarningsErrors()
             parsedArgs.Errors.Verify();
         }
 
+        [Fact]
+        public void WarningVersion()
+        {
+            var parsedArgs = DefaultParse(new string[] { "a.cs" }, WorkingDirectory);
+            parsedArgs.Errors.Verify();
+            Assert.Equal(0m, parsedArgs.CompilationOptions.WarningVersion);
+
+            parsedArgs = DefaultParse(new string[] { "/warnversion", "a.cs" }, WorkingDirectory);
+            parsedArgs.Errors.Verify(
+                Diagnostic(ErrorCode.ERR_SwitchNeedsNumber).WithArguments("warnversion").WithLocation(1, 1)
+                );
+            Assert.Equal(0m, parsedArgs.CompilationOptions.WarningVersion);
+
+            parsedArgs = DefaultParse(new string[] { "/warnversion:", "a.cs" }, WorkingDirectory);
+            parsedArgs.Errors.Verify(
+                Diagnostic(ErrorCode.ERR_SwitchNeedsNumber).WithArguments("warnversion").WithLocation(1, 1)
+                );
+            Assert.Equal(0m, parsedArgs.CompilationOptions.WarningVersion);
+
+            parsedArgs = DefaultParse(new string[] { "/warnversion:-1", "a.cs" }, WorkingDirectory);
+            parsedArgs.Errors.Verify(
+                // Warning version must be greater than or equal to '0'.
+                Diagnostic(ErrorCode.ERR_BadWarningVersion).WithArguments("warnversion").WithLocation(1, 1)
+                );
+            Assert.Equal(0m, parsedArgs.CompilationOptions.WarningVersion);
+
+            parsedArgs = DefaultParse(new string[] { "/warnversion:0", "a.cs" }, WorkingDirectory);
+            parsedArgs.Errors.Verify();
+            Assert.Equal(0m, parsedArgs.CompilationOptions.WarningVersion);
+
+            parsedArgs = DefaultParse(new string[] { "/warnversion:5", "a.cs" }, WorkingDirectory);
+            parsedArgs.Errors.Verify();
+            Assert.Equal(5m, parsedArgs.CompilationOptions.WarningVersion);
+
+            parsedArgs = DefaultParse(new string[] { "/warnversion:5.1", "a.cs" }, WorkingDirectory);
+            parsedArgs.Errors.Verify();
+            Assert.Equal(5.1m, parsedArgs.CompilationOptions.WarningVersion);
+
+            parsedArgs = DefaultParse(new string[] { "/warnversion:9999", "a.cs" }, WorkingDirectory);
+            parsedArgs.Errors.Verify();
+            Assert.Equal(9999m, parsedArgs.CompilationOptions.WarningVersion);
+        }
+
         private static void AssertSpecificDiagnostics(int[] expectedCodes, ReportDiagnostic[] expectedOptions, CSharpCommandLineArguments args)
         {
             var actualOrdered = args.CompilationOptions.SpecificDiagnosticOptions.OrderBy(entry => entry.Key);
@@ -12618,6 +12661,61 @@ public void TestAdditionalFileAnalyzer(bool registerFromInitialize)
 
             CleanupAllGeneratedFiles(srcDirectory.Path);
         }
+
+        [Fact, WorkItem(45702, "https://github.com/dotnet/roslyn/issues/45702")]
+        public void TestWarningVersion()
+        {
+            string source = Temp.CreateFile(prefix: "", extension: ".cs").WriteAllText(@"
+class Program
+{
+    public static void Main() { }
+    public static void M(S s)
+    {
+        if (s == null) { }
+    }
+}
+struct S
+{
+    public static bool operator==(S s1, S s2) => false;
+    public static bool operator!=(S s1, S s2) => true;
+    public override bool Equals(object other) => false;
+    public override int GetHashCode() => 0;
+}
+").Path;
+
+            var baseDir = Path.GetDirectoryName(source);
+            var fileName = Path.GetFileName(source);
+            decimal requiredVersion = ErrorCode.WRN_NubExprIsConstBool2.GetWarningVersion();
+            Assert.Equal(5m, requiredVersion);
+
+            foreach (decimal level in new[] { -1m, 0m, 4m, 4.9m, 5m, 5.0m, 5.1m, 9999m })
+            {
+                var outWriter = new StringWriter(CultureInfo.InvariantCulture);
+                int exitCode = CreateCSharpCompiler(null, baseDir, new[] { "/nologo", "/preferreduilang:en", FormattableString.Invariant($"/warnversion:{level}"), source.ToString() }).Run(outWriter);
+
+                if (level < 0)
+                {
+                    Assert.Equal(1, exitCode);
+                    Assert.Equal(
+                        "error CS8848: Warning version must be greater than or equal to '0'.",
+                        outWriter.ToString().Trim());
+                }
+                else if (level >= requiredVersion)
+                {
+                    Assert.Equal(0, exitCode);
+                    Assert.Equal(
+                        $@"{fileName}(7,13): warning CS8073: The result of the expression is always 'false' since a value of type 'S' is never equal to 'null' of type 'S?'",
+                        outWriter.ToString().Trim());
+                }
+                else
+                {
+                    Assert.Equal(0, exitCode);
+                    Assert.Equal("", outWriter.ToString().Trim());
+                }
+
+                CleanupAllGeneratedFiles(source);
+            }
+        }
     }
 
     [DiagnosticAnalyzer(LanguageNames.CSharp, LanguageNames.VisualBasic)]

src/Compilers/CSharp/Test/Semantic/Semantics/WarningVersionTests.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.UnitTests
+{
+    /// <summary>
+    /// Tests that exercise warnings that are under control of the compiler option <see cref="CSharpCompilationOptions.WarningVersion"/>.
+    /// </summary>
+    public class WarningVersionTests : CompilingTestBase
+    {
+        [Fact]
+        public void CompareStructToNull()
+        {
+            var source = @"
+class Program
+{
+    public static void M(S s)
+    {
+        if (s == null) { }
+        if (s != null) { }
+    }
+}
+struct S
+{
+    public static bool operator==(S s1, S s2) => false;
+    public static bool operator!=(S s1, S s2) => true;
+    public override bool Equals(object other) => false;
+    public override int GetHashCode() => 0;
+}
+";
+            var whenWave5 = new[]
+            {
+                // (6,13): warning CS8073: The result of the expression is always 'false' since a value of type 'S' is never equal to 'null' of type 'S?'
+                //         if (s == null) { }
+                Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "s == null").WithArguments("false", "S", "S?").WithLocation(6, 13),
+                // (7,13): warning CS8073: The result of the expression is always 'true' since a value of type 'S' is never equal to 'null' of type 'S?'
+                //         if (s != null) { }
+                Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "s != null").WithArguments("true", "S", "S?").WithLocation(7, 13)
+            };
+            CreateCompilation(source).VerifyDiagnostics();
+            CreateCompilation(source, options: TestOptions.ReleaseDll.WithWarningVersion(4.9m)).VerifyDiagnostics();
+            CreateCompilation(source, options: TestOptions.ReleaseDll.WithWarningVersion(5m)).VerifyDiagnostics(whenWave5);
+            CreateCompilation(source, options: TestOptions.ReleaseDll.WithWarningVersion(5.0m)).VerifyDiagnostics(whenWave5);
+            CreateCompilation(source, options: TestOptions.ReleaseDll.WithWarningVersion(5.1m)).VerifyDiagnostics(whenWave5);
+        }
+    }
+}

src/Compilers/CSharp/Test/Symbol/Compilation/CSharpCompilationOptionsTests.cs

@@ -367,6 +367,7 @@ public void TestFieldsForEqualsAndGetHashCode()
                 "Language",
                 "AllowUnsafe",
                 "Usings",
+                "WarningVersion",
                 "TopLevelBinderFlags",
                 "NullableContextOptions");
         }

src/EditorFeatures/CSharpTest/Diagnostics/Suppression/RemoveUnnecessaryPragmaSuppressionsTests.cs

@@ -265,23 +265,34 @@ void M()
                 }
             }
 
+            public enum TestKind
+            {
+                Pragmas,
+                SuppressMessageAttributes,
+                PragmasAndSuppressMessageAttributes
+            }
+
             [Theory, CombinatorialData]
-            public async Task TestDoNotRemoveUnsupportedDiagnosticSuppression(bool disable)
+            [WorkItem(46047, "https://github.com/dotnet/roslyn/issues/46047")]
+            public async Task TestDoNotRemoveUnsupportedDiagnosticSuppression(bool disable, TestKind testKind)
             {
                 var disableOrRestore = disable ? "disable" : "restore";
                 var pragmas = new StringBuilder();
                 var suppressMessageAttribtes = new StringBuilder();
                 foreach (var id in UnsupportedDiagnosticIds)
                 {
-                    pragmas.AppendLine($@"#pragma warning {disableOrRestore} {id}");
-                    suppressMessageAttribtes.AppendLine($@"[System.Diagnostics.CodeAnalysis.SuppressMessage(""Category"", ""{id}"")]");
+                    if (testKind == TestKind.Pragmas || testKind == TestKind.PragmasAndSuppressMessageAttributes)
+                        pragmas.AppendLine($@"#pragma warning {disableOrRestore} {id}");
+
+                    if (testKind == TestKind.SuppressMessageAttributes || testKind == TestKind.PragmasAndSuppressMessageAttributes)
+                        suppressMessageAttribtes.AppendLine($@"[System.Diagnostics.CodeAnalysis.SuppressMessage(""Category"", ""{id}"")]");
                 }
 
                 var source = $@"{{|FixAllInDocument:{pragmas}{suppressMessageAttribtes}|}}class Class {{ }}";
 
                 // Compiler diagnostics cannot be suppressed with SuppressMessageAttribute.
                 // Hence, attribute suppressions for compiler diagnostics are always unnecessary.
-                if (!IsCompilerDiagnosticsTest)
+                if (!IsCompilerDiagnosticsTest || testKind == TestKind.Pragmas)
                 {
                     await TestMissingInRegularAndScriptAsync(source);
                 }

src/EditorFeatures/Core/EditorFeaturesResources.resx

@@ -945,4 +945,10 @@ Do you want to proceed?</value>
   <data name="Downloading_IntelliSense_index_for_0" xml:space="preserve">
     <value>Downloading IntelliSense index for {0}</value>
   </data>
+  <data name="Error_creating_instance_of_CodeFixProvider_0" xml:space="preserve">
+    <value>Error creating instance of CodeFixProvider '{0}'</value>
+  </data>
+  <data name="Error_creating_instance_of_CodeFixProvider" xml:space="preserve">
+    <value>Error creating instance of CodeFixProvider</value>
+  </data>
 </root>
\ No newline at end of file

src/EditorFeatures/Core/Implementation/CodeFixes/CodeFixService.cs

@@ -42,13 +42,15 @@ internal partial class CodeFixService : ForegroundThreadAffinitizedObject, ICode
 
         private readonly IDiagnosticAnalyzerService _diagnosticService;
 
-        private readonly ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<DiagnosticId, ImmutableArray<CodeFixProvider>>>> _workspaceFixersMap;
+        private readonly Func<Workspace, ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<DiagnosticId, ImmutableArray<CodeFixProvider>>>>> _getWorkspaceFixersMap;
+        private ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<DiagnosticId, ImmutableArray<CodeFixProvider>>>>? _lazyWorkspaceFixersMap;
         private readonly ConditionalWeakTable<IReadOnlyList<AnalyzerReference>, ImmutableDictionary<DiagnosticId, List<CodeFixProvider>>> _projectFixersMap;
 
         // Shared by project fixers and workspace fixers.
         private ImmutableDictionary<CodeFixProvider, ImmutableArray<DiagnosticId>> _fixerToFixableIdsMap = ImmutableDictionary<CodeFixProvider, ImmutableArray<DiagnosticId>>.Empty;
 
-        private readonly ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<CodeFixProvider, int>>> _fixerPriorityMap;
+        private readonly Func<Workspace, ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<CodeFixProvider, int>>>> _getFixerPriorityMap;
+        private ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<CodeFixProvider, int>>>? _lazyFixerPriorityMap;
 
         private readonly ConditionalWeakTable<AnalyzerReference, ProjectCodeFixProvider> _analyzerReferenceToFixersMap;
         private readonly ConditionalWeakTable<AnalyzerReference, ProjectCodeFixProvider>.CreateValueCallback _createProjectCodeFixProvider;
@@ -62,22 +64,22 @@ internal partial class CodeFixService : ForegroundThreadAffinitizedObject, ICode
         [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
         public CodeFixService(
             IThreadingContext threadingContext,
-            IDiagnosticAnalyzerService service,
+            IDiagnosticAnalyzerService diagnosticAnalyzerService,
             [ImportMany] IEnumerable<Lazy<IErrorLoggerService>> loggers,
             [ImportMany] IEnumerable<Lazy<CodeFixProvider, CodeChangeProviderMetadata>> fixers,
             [ImportMany] IEnumerable<Lazy<IConfigurationFixProvider, CodeChangeProviderMetadata>> configurationProviders)
             : base(threadingContext, assertIsForeground: false)
         {
             _errorLoggers = loggers;
-            _diagnosticService = service;
+            _diagnosticService = diagnosticAnalyzerService;
             var fixersPerLanguageMap = fixers.ToPerLanguageMapWithMultipleLanguages();
             var configurationProvidersPerLanguageMap = configurationProviders.ToPerLanguageMapWithMultipleLanguages();
 
-            _workspaceFixersMap = GetFixerPerLanguageMap(fixersPerLanguageMap, null);
+            _getWorkspaceFixersMap = workspace => GetFixerPerLanguageMap(fixersPerLanguageMap, workspace);
             _configurationProvidersMap = GetConfigurationProvidersPerLanguageMap(configurationProvidersPerLanguageMap);
 
             // REVIEW: currently, fixer's priority is statically defined by the fixer itself. might considering making it more dynamic or configurable.
-            _fixerPriorityMap = GetFixerPriorityPerLanguageMap(fixersPerLanguageMap);
+            _getFixerPriorityMap = workspace => GetFixerPriorityPerLanguageMap(fixersPerLanguageMap, workspace);
 
             // Per-project fixers
             _projectFixersMap = new ConditionalWeakTable<IReadOnlyList<AnalyzerReference>, ImmutableDictionary<string, List<CodeFixProvider>>>();
@@ -202,7 +204,7 @@ public async Task<ImmutableArray<CodeFixCollection>> GetFixesAsync(Document docu
                     result, addOperationScope, cancellationToken).ConfigureAwait(false);
             }
 
-            if (result.Count > 0 && _fixerPriorityMap.TryGetValue(document.Project.Language, out var fixersForLanguage))
+            if (result.Count > 0 && TryGetWorkspaceFixersPriorityMap(document, out var fixersForLanguage))
             {
                 // sort the result to the order defined by the fixers
 #pragma warning disable IDE0007 // Use implicit type - Explicit type is need to suppress an incorrect nullable warning on dereferencing the map.
@@ -266,6 +268,68 @@ public async Task<Document> ApplyCodeFixesForSpecificDiagnosticIdAsync(Document
             return solution.GetDocument(document.Id) ?? throw new NotSupportedException(EditorFeaturesResources.Removal_of_document_not_supported);
         }
 
+        private bool TryGetWorkspaceFixersMap(Document document, out Lazy<ImmutableDictionary<DiagnosticId, ImmutableArray<CodeFixProvider>>> fixerMap)
+        {
+            if (_lazyWorkspaceFixersMap == null)
+            {
+                var workspaceFixersMap = _getWorkspaceFixersMap(document.Project.Solution.Workspace);
+                Interlocked.CompareExchange(ref _lazyWorkspaceFixersMap, workspaceFixersMap, null);
+            }
+
+            return _lazyWorkspaceFixersMap.TryGetValue(document.Project.Language, out fixerMap);
+        }
+
+        private bool TryGetWorkspaceFixersPriorityMap(Document document, out Lazy<ImmutableDictionary<CodeFixProvider, int>> fixersPriorityMap)
+        {
+            if (_lazyFixerPriorityMap == null)
+            {
+                var fixersPriorityByLanguageMap = _getFixerPriorityMap(document.Project.Solution.Workspace);
+                Interlocked.CompareExchange(ref _lazyFixerPriorityMap, fixersPriorityByLanguageMap, null);
+            }
+
+            return _lazyFixerPriorityMap.TryGetValue(document.Project.Language, out fixersPriorityMap);
+        }
+
+        private bool TryGetWorkspaceFixer(
+            Lazy<CodeFixProvider, CodeChangeProviderMetadata> lazyFixer,
+            Workspace workspace,
+            bool logExceptionWithInfoBar,
+            [NotNullWhen(returnValue: true)] out CodeFixProvider? fixer)
+        {
+            try
+            {
+                fixer = lazyFixer.Value;
+                return true;
+            }
+            catch (Exception ex)
+            {
+                // Gracefully handle exceptions in creating fixer instance.
+                // Log exception and show info bar, if needed.
+                if (logExceptionWithInfoBar)
+                {
+                    var errorReportingService = workspace.Services.GetRequiredService<IErrorReportingService>();
+                    var message = lazyFixer.Metadata.Name != null
+                        ? string.Format(EditorFeaturesResources.Error_creating_instance_of_CodeFixProvider_0, lazyFixer.Metadata.Name)
+                        : EditorFeaturesResources.Error_creating_instance_of_CodeFixProvider;
+
+                    errorReportingService.ShowErrorInfoInActiveView(
+                        message,
+                        new InfoBarUI(
+                            WorkspacesResources.Show_Stack_Trace,
+                            InfoBarUI.UIKind.HyperLink,
+                            () => errorReportingService.ShowDetailedErrorInfo(ex), closeAfterAction: true));
+
+                    foreach (var errorLogger in _errorLoggers)
+                    {
+                        errorLogger.Value.LogException(this, ex);
+                    }
+                }
+
+                fixer = null;
+                return false;
+            }
+        }
+
         private async Task AppendFixesAsync(
             Document document,
             TextSpan span,
@@ -276,7 +340,7 @@ public async Task<Document> ApplyCodeFixesForSpecificDiagnosticIdAsync(Document
             Func<string, IDisposable?> addOperationScope,
             CancellationToken cancellationToken)
         {
-            var hasAnySharedFixer = _workspaceFixersMap.TryGetValue(document.Project.Language, out var fixerMap);
+            var hasAnySharedFixer = TryGetWorkspaceFixersMap(document, out var fixerMap);
 
             var projectFixersMap = GetProjectFixers(document.Project);
             var hasAnyProjectFixer = projectFixersMap.Any();
@@ -615,7 +679,7 @@ private async Task<IEnumerable<Diagnostic>> GetProjectDiagnosticsAsync(Project p
             Document document, DiagnosticData diagnostic, CancellationToken cancellationToken)
         {
             var workspaceFixers = ImmutableArray<CodeFixProvider>.Empty;
-            var hasAnySharedFixer = _workspaceFixersMap.TryGetValue(document.Project.Language, out var fixerMap) && fixerMap.Value.TryGetValue(diagnostic.Id, out workspaceFixers);
+            var hasAnySharedFixer = TryGetWorkspaceFixersMap(document, out var fixerMap) && fixerMap.Value.TryGetValue(diagnostic.Id, out workspaceFixers);
             var hasAnyProjectFixer = GetProjectFixers(document.Project).TryGetValue(diagnostic.Id, out var projectFixers);
 
             // TODO (https://github.com/dotnet/roslyn/issues/4932): Don't restrict CodeFixes in Interactive
@@ -755,18 +819,24 @@ private static ImmutableArray<string> GetAndTestFixableDiagnosticIds(CodeFixProv
 
         private ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<DiagnosticId, ImmutableArray<CodeFixProvider>>>> GetFixerPerLanguageMap(
             Dictionary<LanguageKind, List<Lazy<CodeFixProvider, CodeChangeProviderMetadata>>> fixersPerLanguage,
-            IExtensionManager? extensionManager)
+            Workspace workspace)
         {
             var fixerMap = ImmutableDictionary.Create<LanguageKind, Lazy<ImmutableDictionary<DiagnosticId, ImmutableArray<CodeFixProvider>>>>();
+            var extensionManager = workspace.Services.GetService<IExtensionManager>();
             foreach (var languageKindAndFixers in fixersPerLanguage)
             {
                 var lazyMap = new Lazy<ImmutableDictionary<DiagnosticId, ImmutableArray<CodeFixProvider>>>(() =>
                 {
                     var mutableMap = new Dictionary<DiagnosticId, List<CodeFixProvider>>();
 
-                    foreach (var fixer in languageKindAndFixers.Value)
+                    foreach (var lazyFixer in languageKindAndFixers.Value)
                     {
-                        foreach (var id in this.GetFixableDiagnosticIds(fixer.Value, extensionManager))
+                        if (!TryGetWorkspaceFixer(lazyFixer, workspace, logExceptionWithInfoBar: true, out var fixer))
+                        {
+                            continue;
+                        }
+
+                        foreach (var id in this.GetFixableDiagnosticIds(fixer, extensionManager))
                         {
                             if (string.IsNullOrWhiteSpace(id))
                             {
@@ -774,7 +844,7 @@ private static ImmutableArray<string> GetAndTestFixableDiagnosticIds(CodeFixProv
                             }
 
                             var list = mutableMap.GetOrAdd(id, s_createList);
-                            list.Add(fixer.Value);
+                            list.Add(fixer);
                         }
                     }
 
@@ -818,8 +888,9 @@ static ImmutableArray<IConfigurationFixProvider> GetConfigurationFixProviders(Li
             }
         }
 
-        private static ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<CodeFixProvider, int>>> GetFixerPriorityPerLanguageMap(
-            Dictionary<LanguageKind, List<Lazy<CodeFixProvider, CodeChangeProviderMetadata>>> fixersPerLanguage)
+        private ImmutableDictionary<LanguageKind, Lazy<ImmutableDictionary<CodeFixProvider, int>>> GetFixerPriorityPerLanguageMap(
+            Dictionary<LanguageKind, List<Lazy<CodeFixProvider, CodeChangeProviderMetadata>>> fixersPerLanguage,
+            Workspace workspace)
         {
             var languageMap = ImmutableDictionary.CreateBuilder<LanguageKind, Lazy<ImmutableDictionary<CodeFixProvider, int>>>();
             foreach (var languageAndFixers in fixersPerLanguage)
@@ -828,10 +899,15 @@ static ImmutableArray<IConfigurationFixProvider> GetConfigurationFixProviders(Li
                 {
                     var priorityMap = ImmutableDictionary.CreateBuilder<CodeFixProvider, int>();
 
-                    var fixers = ExtensionOrderer.Order(languageAndFixers.Value);
-                    for (var i = 0; i < fixers.Count; i++)
+                    var lazyFixers = ExtensionOrderer.Order(languageAndFixers.Value);
+                    for (var i = 0; i < lazyFixers.Count; i++)
                     {
-                        priorityMap.Add(fixers[i].Value, i);
+                        if (!TryGetWorkspaceFixer(lazyFixers[i], workspace, logExceptionWithInfoBar: false, out var fixer))
+                        {
+                            continue;
+                        }
+
+                        priorityMap.Add(fixer, i);
                     }
 
                     return priorityMap.ToImmutable();

src/EditorFeatures/Core/xlf/EditorFeaturesResources.cs.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">položky z neimportovaných oborů názvů</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.de.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">Elemente aus nicht importierten Namespaces</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.es.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">elementos de espacios de nombres no importados</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.fr.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">éléments provenant d'espaces de noms non importés</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.it.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">elementi da spazi dei nomi non importati</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ja.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">インポートされていない名前空間の項目</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ko.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">가져오지 않은 네임스페이스의 항목</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.pl.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">elementy z nieimportowanych przestrzeni nazw</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.pt-BR.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">itens de namespaces não importados</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ru.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">элементы из неимпортированных пространств имен</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.tr.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">içeri aktarılmayan ad alanlarındaki öğeler</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.zh-Hans.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">未导入命名空间中的项</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.zh-Hant.xlf

@@ -52,6 +52,16 @@
         <target state="new">Downloading index failed:{0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider">
+        <source>Error creating instance of CodeFixProvider</source>
+        <target state="new">Error creating instance of CodeFixProvider</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="Error_creating_instance_of_CodeFixProvider_0">
+        <source>Error creating instance of CodeFixProvider '{0}'</source>
+        <target state="new">Error creating instance of CodeFixProvider '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Expander_display_text">
         <source>items from unimported namespaces</source>
         <target state="translated">來自未匯入命名空間的項目</target>

src/EditorFeatures/Test/CodeFixes/CodeFixServiceTests.cs

@@ -139,14 +139,14 @@ public async Task TestGetCodeFixWithExceptionInRegisterMethodAsync()
         [Fact]
         public async Task TestGetCodeFixWithExceptionInFixableDiagnosticIds()
         {
-            await GetDefaultFixesAsync(new ErrorCases.ExceptionInFixableDiagnosticIds());
+            await GetFirstDiagnosticWithFixAsync(new ErrorCases.ExceptionInFixableDiagnosticIds());
             await GetAddedFixesWithExceptionValidationAsync(new ErrorCases.ExceptionInFixableDiagnosticIds());
         }
 
         [Fact(Skip = "https://github.com/dotnet/roslyn/issues/21533")]
         public async Task TestGetCodeFixWithExceptionInFixableDiagnosticIds2()
         {
-            await GetDefaultFixesAsync(new ErrorCases.ExceptionInFixableDiagnosticIds2());
+            await GetFirstDiagnosticWithFixAsync(new ErrorCases.ExceptionInFixableDiagnosticIds2());
             await GetAddedFixesWithExceptionValidationAsync(new ErrorCases.ExceptionInFixableDiagnosticIds2());
         }
 
@@ -154,23 +154,19 @@ public async Task TestGetCodeFixWithExceptionInFixableDiagnosticIds2()
         public async Task TestGetCodeFixWithExceptionInGetFixAllProvider()
             => await GetAddedFixesWithExceptionValidationAsync(new ErrorCases.ExceptionInGetFixAllProvider());
 
-        private static async Task GetDefaultFixesAsync(CodeFixProvider codefix)
-        {
-            var tuple = ServiceSetup(codefix);
-            using var workspace = tuple.workspace;
-
-            GetDocumentAndExtensionManager(tuple.analyzerService, workspace, out var document, out var extensionManager);
-            var fixes = await tuple.codeFixService.GetFixesAsync(document, TextSpan.FromBounds(0, 0), includeConfigurationFixes: true, cancellationToken: CancellationToken.None);
-            Assert.True(((TestErrorLogger)tuple.errorLogger).Messages.Count == 1);
-            Assert.True(((TestErrorLogger)tuple.errorLogger).Messages.TryGetValue(codefix.GetType().Name, out var message));
-        }
+        [Fact, WorkItem(45851, "https://github.com/dotnet/roslyn/issues/45851")]
+        public async Task TestGetCodeFixWithExceptionOnCodeFixProviderCreation()
+            => await GetAddedFixesAsync(
+                new MockFixer(),
+                new MockAnalyzerReference.MockDiagnosticAnalyzer(),
+                throwExceptionInFixerCreation: true);
 
         private static Task<ImmutableArray<CodeFixCollection>> GetAddedFixesWithExceptionValidationAsync(CodeFixProvider codefix)
             => GetAddedFixesAsync(codefix, diagnosticAnalyzer: new MockAnalyzerReference.MockDiagnosticAnalyzer(), exception: true);
 
-        private static async Task<ImmutableArray<CodeFixCollection>> GetAddedFixesAsync(CodeFixProvider codefix, DiagnosticAnalyzer diagnosticAnalyzer, bool exception = false)
+        private static async Task<ImmutableArray<CodeFixCollection>> GetAddedFixesAsync(CodeFixProvider codefix, DiagnosticAnalyzer diagnosticAnalyzer, bool exception = false, bool throwExceptionInFixerCreation = false)
         {
-            var tuple = ServiceSetup(codefix);
+            var tuple = ServiceSetup(codefix, throwExceptionInFixerCreation: throwExceptionInFixerCreation);
 
             using var workspace = tuple.workspace;
 
@@ -203,11 +199,12 @@ private static async Task GetFirstDiagnosticWithFixAsync(CodeFixProvider codefix
 
         private static (TestWorkspace workspace, TestDiagnosticAnalyzerService analyzerService, CodeFixService codeFixService, IErrorLoggerService errorLogger) ServiceSetup(
             CodeFixProvider codefix,
-            bool includeConfigurationFixProviders = false)
+            bool includeConfigurationFixProviders = false,
+            bool throwExceptionInFixerCreation = false)
         {
             var fixers = SpecializedCollections.SingletonEnumerable(
                 new Lazy<CodeFixProvider, CodeChangeProviderMetadata>(
-                () => codefix,
+                () => throwExceptionInFixerCreation ? throw new Exception() : codefix,
                 new CodeChangeProviderMetadata("Test", languages: LanguageNames.CSharp)));
 
             var code = @"class Program { }";