Faster suppressions

src/Compilers/Core/Portable/CommandLine/CommonCompiler.SuppressionDiagnostic.cs

@@ -69,15 +69,15 @@ public override string GetMessage(IFormatProvider formatProvider = null)
 
             public override bool Equals(Diagnostic obj)
             {
-                var other = obj as SuppressionDiagnostic;
-                if (other == null)
+                if (ReferenceEquals(this, obj))
                 {
-                    return false;
+                    return true;
                 }
 
-                if (ReferenceEquals(this, other))
+                var other = obj as SuppressionDiagnostic;
+                if (other == null)
                 {
-                    return true;
+                    return false;
                 }
 
                 return Equals(_originalDiagnostic, other._originalDiagnostic) &&

src/Compilers/Core/Portable/Diagnostic/Diagnostic.DiagnosticWithProgrammaticSuppression.cs

@@ -87,15 +87,15 @@ public override ImmutableDictionary<string, string> Properties
 
             public override bool Equals(Diagnostic? obj)
             {
-                var other = obj as DiagnosticWithProgrammaticSuppression;
-                if (other == null)
+                if (ReferenceEquals(this, obj))
                 {
-                    return false;
+                    return true;
                 }
 
-                if (ReferenceEquals(this, other))
+                var other = obj as DiagnosticWithProgrammaticSuppression;
+                if (other == null)
                 {
-                    return true;
+                    return false;
                 }
 
                 return Equals(_originalUnsuppressedDiagnostic, other._originalUnsuppressedDiagnostic) &&

src/Compilers/Core/Portable/Diagnostic/DiagnosticDescriptor.cs

@@ -173,6 +173,11 @@ internal DiagnosticDescriptor(
 
         public bool Equals(DiagnosticDescriptor? other)
         {
+            if (ReferenceEquals(this, other))
+            {
+                return true;
+            }
+
             return
                 other != null &&
                 this.Category == other.Category &&

src/Compilers/Core/Portable/Diagnostic/DiagnosticWithInfo.cs

@@ -150,7 +150,7 @@ public override bool Equals(object? obj)
 
         public override bool Equals(Diagnostic? obj)
         {
-            if (this == obj)
+            if (ReferenceEquals(this, obj))
             {
                 return true;
             }

src/Compilers/Core/Portable/Diagnostic/Diagnostic_SimpleDiagnostic.cs

@@ -146,6 +146,11 @@ public override ImmutableDictionary<string, string> Properties
 
             public override bool Equals(Diagnostic? obj)
             {
+                if (ReferenceEquals(this, obj))
+                {
+                    return true;
+                }
+
                 var other = obj as SimpleDiagnostic;
                 if (other == null)
                 {

src/Compilers/Core/Portable/DiagnosticAnalyzer/Suppression.cs

@@ -3,14 +3,16 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.Diagnostics
 {
     /// <summary>
     /// Programmatic suppression of a <see cref="Diagnostic"/> by a <see cref="DiagnosticSuppressor"/>.
     /// </summary>
-    public struct Suppression
+    public struct Suppression : IEquatable<Suppression>
     {
         private Suppression(SuppressionDescriptor descriptor, Diagnostic suppressedDiagnostic)
         {
@@ -48,5 +50,34 @@ public static Suppression Create(SuppressionDescriptor descriptor, Diagnostic su
         /// Diagnostic suppressed by this suppression.
         /// </summary>
         public Diagnostic SuppressedDiagnostic { get; }
+
+        public static bool operator ==(Suppression left, Suppression right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(Suppression left, Suppression right)
+        {
+            return !(left == right);
+        }
+
+        public override bool Equals(object obj)
+        {
+            return obj is Suppression suppression
+                && Equals(suppression);
+        }
+
+        public bool Equals(Suppression other)
+        {
+            return EqualityComparer<SuppressionDescriptor>.Default.Equals(Descriptor, other.Descriptor)
+                && EqualityComparer<Diagnostic>.Default.Equals(SuppressedDiagnostic, other.SuppressedDiagnostic);
+        }
+
+        public override int GetHashCode()
+        {
+            return Hash.Combine(
+                EqualityComparer<SuppressionDescriptor>.Default.GetHashCode(Descriptor),
+                EqualityComparer<Diagnostic>.Default.GetHashCode(SuppressedDiagnostic));
+        }
     }
 }

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

@@ -1,5 +1,6 @@
 Microsoft.CodeAnalysis.CommandLineSourceFile.CommandLineSourceFile(string path, bool isScript, bool isInputRedirected) -> void
 Microsoft.CodeAnalysis.CommandLineSourceFile.IsInputRedirected.get -> bool
+Microsoft.CodeAnalysis.Diagnostics.Suppression.Equals(Microsoft.CodeAnalysis.Diagnostics.Suppression other) -> bool
 Microsoft.CodeAnalysis.GeneratorAttribute
 Microsoft.CodeAnalysis.GeneratorAttribute.GeneratorAttribute() -> void
 Microsoft.CodeAnalysis.GeneratorDriver
@@ -25,5 +26,9 @@ Microsoft.CodeAnalysis.SourceGeneratorContext.ReportDiagnostic(Microsoft.CodeAna
 Microsoft.CodeAnalysis.SourceGeneratorContext.SyntaxReceiver.get -> Microsoft.CodeAnalysis.ISyntaxReceiver
 Microsoft.CodeAnalysis.SyntaxReceiverCreator
 override Microsoft.CodeAnalysis.Diagnostics.AnalyzerFileReference.GetGenerators() -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.ISourceGenerator>
+override Microsoft.CodeAnalysis.Diagnostics.Suppression.Equals(object obj) -> bool
+override Microsoft.CodeAnalysis.Diagnostics.Suppression.GetHashCode() -> int
+static Microsoft.CodeAnalysis.Diagnostics.Suppression.operator !=(Microsoft.CodeAnalysis.Diagnostics.Suppression left, Microsoft.CodeAnalysis.Diagnostics.Suppression right) -> bool
+static Microsoft.CodeAnalysis.Diagnostics.Suppression.operator ==(Microsoft.CodeAnalysis.Diagnostics.Suppression left, Microsoft.CodeAnalysis.Diagnostics.Suppression right) -> bool
 virtual Microsoft.CodeAnalysis.Diagnostics.AnalyzerReference.GetGenerators() -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.ISourceGenerator>
 const Microsoft.CodeAnalysis.WellKnownDiagnosticTags.CustomObsolete = "CustomObsolete" -> string