Faster null checks

src/System.Private.CoreLib/shared/System/DefaultBinder.cs

@@ -102,7 +102,7 @@ public sealed override MethodBase BindToMethod(
                 paramArrayType = null;
 
                 // If we have named parameters then we may have a hole in the candidates array.
-                if (candidates[i] == null)
+                if (candidates[i] is null)
                     continue;
 
                 // Validate the parameters.
@@ -838,10 +838,15 @@ public static PropertyInfo ExactPropertyBinding(PropertyInfo[] match, Type retur
                 if (returnType != null && returnType != match[i].PropertyType)
                     continue;
 
-                if (bestMatch != null)
+                if (bestMatch is null)
+                {
+                    bestMatch = match[i];
+                }
+                else
+                {
                     throw new AmbiguousMatchException(SR.Arg_AmbiguousMatchException);
+                }
 
-                bestMatch = match[i];
             }
             return bestMatch;
         }

src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/EventSource.cs

@@ -317,7 +317,7 @@ public EventSourceSettings Settings
         /// </summary>
         public static Guid GetGuid(Type eventSourceType)
         {
-            if (eventSourceType == null)
+            if (eventSourceType is null)
                 throw new ArgumentNullException(nameof(eventSourceType));
 
             EventSourceAttribute attrib = (EventSourceAttribute)GetCustomAttributeHelper(eventSourceType, typeof(EventSourceAttribute));
@@ -384,7 +384,7 @@ public static string GenerateManifest(Type eventSourceType, string assemblyPathT
         /// <returns>The XML data string or null</returns>
         public static string GenerateManifest(Type eventSourceType, string assemblyPathToIncludeInManifest, EventManifestOptions flags)
         {
-            if (eventSourceType == null)
+            if (eventSourceType is null)
                 throw new ArgumentNullException(nameof(eventSourceType));
 
             byte[] manifestBytes = EventSource.CreateManifestAndDescriptors(eventSourceType, assemblyPathToIncludeInManifest, null, flags);
@@ -1461,7 +1461,7 @@ private unsafe void Initialize(Guid eventSourceGuid, string eventSourceName, str
 
         private static string GetName(Type eventSourceType, EventManifestOptions flags)
         {
-            if (eventSourceType == null)
+            if (eventSourceType is null)
                 throw new ArgumentNullException(nameof(eventSourceType));
 
             EventSourceAttribute attrib = (EventSourceAttribute)GetCustomAttributeHelper(eventSourceType, typeof(EventSourceAttribute), flags);

src/System.Private.CoreLib/shared/System/Diagnostics/Tracing/TraceLogging/TypeAnalysis.cs

@@ -47,7 +47,7 @@ public TypeAnalysis(
                 }
 
                 MethodInfo getterInfo = Statics.GetGetMethod(propertyInfo);
-                if (getterInfo == null)
+                if (getterInfo is null)
                 {
                     continue;
                 }

src/System.Private.CoreLib/shared/System/Reflection/Assembly.cs

@@ -24,7 +24,7 @@ public virtual IEnumerable<TypeInfo> DefinedTypes
                 for (int i = 0; i < types.Length; i++)
                 {
                     TypeInfo typeinfo = types[i].GetTypeInfo();
-                    if (typeinfo == null)
+                    if (typeinfo is null)
                         throw new NotSupportedException(SR.Format(SR.NotSupported_NoTypeInfo, types[i].FullName));
 
                     typeinfos[i] = typeinfo;
@@ -100,7 +100,7 @@ public virtual Type[] GetTypes()
         public virtual object CreateInstance(string typeName, bool ignoreCase, BindingFlags bindingAttr, Binder binder, object[] args, CultureInfo culture, object[] activationAttributes)
         {
             Type t = GetType(typeName, throwOnError: false, ignoreCase: ignoreCase);
-            if (t == null)
+            if (t is null)
                 return null;
 
             return Activator.CreateInstance(t, bindingAttr, binder, args, culture, activationAttributes);
@@ -167,11 +167,11 @@ public override string ToString()
 
         public static Assembly GetAssembly(Type type)
         {
-            if (type == null)
+            if (type is null)
                 throw new ArgumentNullException(nameof(type));
 
             Module m = type.Module;
-            if (m == null)
+            if (m is null)
                 return null;
             else
                 return m.Assembly;

src/System.Private.CoreLib/shared/System/Reflection/ConstructorInfo.cs

@@ -23,13 +23,12 @@ protected ConstructorInfo() { }
 
         public static bool operator ==(ConstructorInfo left, ConstructorInfo right)
         {
-            if (object.ReferenceEquals(left, right))
+            if (ReferenceEquals(left, right))
+            {
                 return true;
+            }
 
-            if ((object)left == null || (object)right == null)
-                return false;
-
-            return left.Equals(right);
+            return (left is null || right is null) ? false : left.Equals(right);
         }
 
         public static bool operator !=(ConstructorInfo left, ConstructorInfo right) => !(left == right);

src/System.Private.CoreLib/shared/System/Reflection/EventInfo.cs

@@ -67,7 +67,7 @@ public virtual void AddEventHandler(object target, Delegate handler)
         {
             MethodInfo addMethod = GetAddMethod(nonPublic: false);
 
-            if (addMethod == null)
+            if (addMethod is null)
                 throw new InvalidOperationException(SR.InvalidOperation_NoPublicAddMethod);
 
 #if FEATURE_COMINTEROP
@@ -84,7 +84,7 @@ public virtual void RemoveEventHandler(object target, Delegate handler)
         {
             MethodInfo removeMethod = GetRemoveMethod(nonPublic: false);
 
-            if (removeMethod == null)
+            if (removeMethod is null)
                 throw new InvalidOperationException(SR.InvalidOperation_NoPublicRemoveMethod);
 
 #if FEATURE_COMINTEROP
@@ -101,11 +101,15 @@ public virtual void RemoveEventHandler(object target, Delegate handler)
 
         public static bool operator ==(EventInfo left, EventInfo right)
         {
-            if (object.ReferenceEquals(left, right))
+            if (ReferenceEquals(left, right))
+            {
                 return true;
+            }
 
-            if ((object)left == null || (object)right == null)
+            if (left is null || right is null)
+            {
                 return false;
+            }
 
             return left.Equals(right);
         }

src/System.Private.CoreLib/shared/System/Reflection/FieldInfo.cs

@@ -41,13 +41,12 @@ protected FieldInfo() { }
 
         public static bool operator ==(FieldInfo left, FieldInfo right)
         {
-            if (object.ReferenceEquals(left, right))
+            if (ReferenceEquals(left, right))
+            {
                 return true;
+            }
 
-            if ((object)left == null || (object)right == null)
-                return false;
-
-            return left.Equals(right);
+            return (left is null || right is null) ? false : left.Equals(right);
         }
 
         public static bool operator !=(FieldInfo left, FieldInfo right) => !(left == right);

src/System.Private.CoreLib/shared/System/Reflection/IntrospectionExtensions.cs

@@ -10,7 +10,7 @@ public static class IntrospectionExtensions
     {
         public static TypeInfo GetTypeInfo(this Type type)
         {
-            if (type == null)
+            if (type is null)
                 throw new ArgumentNullException(nameof(type));
 
             if (type is IReflectableType reflectableType)

src/System.Private.CoreLib/shared/System/Reflection/MemberInfo.cs

@@ -22,9 +22,10 @@ public virtual Module Module
                 // This check is necessary because for some reason, Type adds a new "Module" property that hides the inherited one instead 
                 // of overriding.
 
-                Type type = this as Type;
-                if (type != null)
+                if (this is Type type)
+                {
                     return type.Module;
+                }
 
                 throw NotImplemented.ByDesign;
             }
@@ -46,28 +47,48 @@ public virtual Module Module
 
         public static bool operator ==(MemberInfo left, MemberInfo right)
         {
-            if (object.ReferenceEquals(left, right))
+            if (ReferenceEquals(left, right))
+            {
                 return true;
+            }
 
-            if ((object)left == null || (object)right == null)
+            if (left is null || right is null)
+            {
                 return false;
+            }
+
+            if (left is Type type1)
+            {
+                // Type has special handling via operator== 
+                return (right is Type type2) ? type1 == type2 : false;
+            }
+
+            if (left is MethodBase method1)
+            {
+                // MethodBase has special handling via operator== 
+                return (right is MethodBase method2) ? method1 == method2 : false;
+            }
 
-            Type type1, type2;
-            MethodBase method1, method2;
-            FieldInfo field1, field2;
-            EventInfo event1, event2;
-            PropertyInfo property1, property2;
-
-            if ((type1 = left as Type) != null && (type2 = right as Type) != null)
-                return type1 == type2;
-            else if ((method1 = left as MethodBase) != null && (method2 = right as MethodBase) != null)
-                return method1 == method2;
-            else if ((field1 = left as FieldInfo) != null && (field2 = right as FieldInfo) != null)
-                return field1 == field2;
-            else if ((event1 = left as EventInfo) != null && (event2 = right as EventInfo) != null)
-                return event1 == event2;
-            else if ((property1 = left as PropertyInfo) != null && (property2 = right as PropertyInfo) != null)
-                return property1 == property2;
+            if (left is FieldInfo field1)
+            {
+                // FieldInfo operator== calls Equals after same reference and null checks above,
+                // so just call Equals directly.
+                return (right is FieldInfo field2) ? field1.Equals(field2) : false;
+            }
+
+            if (left is EventInfo event1)
+            {
+                // EventInfo operator== calls Equals after same reference and null checks above,
+                // so just call Equals directly.
+                return (right is EventInfo event2) ? event1.Equals(event2) : false;
+            }
+
+            if (left is PropertyInfo property1)
+            {
+                // PropertyInfo operator== calls Equals after same reference and null checks above,
+                // so just call Equals directly.
+                return (right is PropertyInfo property2) ? property1.Equals(property2) : false;
+            }
 
             return false;
         }

src/System.Private.CoreLib/shared/System/Reflection/MethodBase.cs

@@ -64,19 +64,29 @@ public bool IsConstructor
 
         public static bool operator ==(MethodBase left, MethodBase right)
         {
-            if (object.ReferenceEquals(left, right))
+            if (ReferenceEquals(left, right))
+            {
                 return true;
+            }
 
-            if ((object)left == null || (object)right == null)
+            if (left is null || right is null)
+            {
                 return false;
+            }
 
-            MethodInfo method1, method2;
-            ConstructorInfo constructor1, constructor2;
+            if (left is MethodInfo method1)
+            {
+                // MethodInfo operator== calls Equals after same reference and null checks above,
+                // so just call Equals directly.
+                return (right is MethodInfo method2) ? method1.Equals(method2) : false;
+            }
 
-            if ((method1 = left as MethodInfo) != null && (method2 = right as MethodInfo) != null)
-                return method1 == method2;
-            else if ((constructor1 = left as ConstructorInfo) != null && (constructor2 = right as ConstructorInfo) != null)
-                return constructor1 == constructor2;
+            if (left is ConstructorInfo constructor1)
+            {
+                // ConstructorInfo operator== calls Equals after same reference and null checks above,
+                // so just call Equals directly.
+                return (right is ConstructorInfo constructor2) ? constructor1.Equals(constructor2) : false;
+            }
 
             return false;
         }

src/System.Private.CoreLib/shared/System/Reflection/MethodInfo.cs

@@ -29,13 +29,12 @@ protected MethodInfo() { }
 
         public static bool operator ==(MethodInfo left, MethodInfo right)
         {
-            if (object.ReferenceEquals(left, right))
+            if (ReferenceEquals(left, right))
+            {
                 return true;
+            }
 
-            if ((object)left == null || (object)right == null)
-                return false;
-
-            return left.Equals(right);
+            return (left is null || right is null) ? false : left.Equals(right);
         }
 
         public static bool operator !=(MethodInfo left, MethodInfo right) => !(left == right);

src/System.Private.CoreLib/shared/System/Reflection/Module.cs

@@ -46,7 +46,7 @@ public MethodInfo GetMethod(string name, BindingFlags bindingAttr, Binder binder
                 throw new ArgumentNullException(nameof(types));
             for (int i = 0; i < types.Length; i++)
             {
-                if (types[i] == null)
+                if (types[i] is null)
                     throw new ArgumentNullException(nameof(types));
             }
             return GetMethodImpl(name, bindingAttr, binder, callConvention, types, modifiers);

src/System.Private.CoreLib/shared/System/Reflection/ParameterInfo.cs

@@ -29,7 +29,7 @@ protected ParameterInfo() { }
 
         public virtual bool IsDefined(Type attributeType, bool inherit)
         {
-            if (attributeType == null)
+            if (attributeType is null)
                 throw new ArgumentNullException(nameof(attributeType));
 
             return false;
@@ -41,7 +41,7 @@ public virtual bool IsDefined(Type attributeType, bool inherit)
         public virtual object[] GetCustomAttributes(bool inherit) => Array.Empty<object>();
         public virtual object[] GetCustomAttributes(Type attributeType, bool inherit)
         {
-            if (attributeType == null)
+            if (attributeType is null)
                 throw new ArgumentNullException(nameof(attributeType));
 
             return Array.Empty<object>();
@@ -57,7 +57,7 @@ public object GetRealObject(StreamingContext context)
             // Once all the serializable fields have come in we can set up the real
             // instance based on just two of them (MemberImpl and PositionImpl).
 
-            if (MemberImpl == null)
+            if (MemberImpl is null)
                 throw new SerializationException(SR.Serialization_InsufficientState);
 
             ParameterInfo[] args = null;

src/System.Private.CoreLib/shared/System/Reflection/Pointer.cs

@@ -23,7 +23,7 @@ private Pointer(void* ptr, Type ptrType)
 
         public static object Box(void* ptr, Type type)
         {
-            if (type == null)
+            if (type is null)
                 throw new ArgumentNullException(nameof(type));
             if (!type.IsPointer)
                 throw new ArgumentException(SR.Arg_MustBePointer, nameof(ptr));

src/System.Private.CoreLib/shared/System/Reflection/PropertyInfo.cs

@@ -60,11 +60,15 @@ protected PropertyInfo() { }
 
         public static bool operator ==(PropertyInfo left, PropertyInfo right)
         {
-            if (object.ReferenceEquals(left, right))
+            if (ReferenceEquals(left, right))
+            {
                 return true;
+            }
 
-            if ((object)left == null || (object)right == null)
+            if (left is null || right is null)
+            {
                 return false;
+            }
 
             return left.Equals(right);
         }

src/System.Private.CoreLib/shared/System/Reflection/SignatureConstructedGenericType.cs

@@ -14,7 +14,7 @@ internal sealed class SignatureConstructedGenericType : SignatureType
         // intended user of this constructor.
         internal SignatureConstructedGenericType(Type genericTypeDefinition, Type[] typeArguments)
         {
-            if (genericTypeDefinition == null)
+            if (genericTypeDefinition is null)
                 throw new ArgumentNullException(nameof(genericTypeDefinition));
 
             if (typeArguments == null)
@@ -23,7 +23,7 @@ internal SignatureConstructedGenericType(Type genericTypeDefinition, Type[] type
             typeArguments = (Type[])(typeArguments.Clone());
             for (int i = 0; i < typeArguments.Length; i++)
             {
-                if (typeArguments[i] == null)
+                if (typeArguments[i] is null)
                     throw new ArgumentNullException(nameof(typeArguments));
             }