Use [NotNullWhen(true)] in more places (#47598)

* Use [NotNullWhen(true)] in more places

Did a quick search/audit for methods that returned bool and took nullable object as the first input, and added [NotNullWhen(true)] where it was obviously correct.

* Address PR feedback

Author: stephentoub

docs/coding-guidelines/api-guidelines/nullability.md

@@ -96,6 +96,7 @@ The C# compiler respects a set of attributes that impact its flow analysis.  We
 - **DO** annotate properties where a getter will never return `null` but a setter allows `null` as being non-nullable but also `[AllowNull]`.
 - **DO** annotate properties where a getter may return `null` but a setter throws for `null` as being nullable but also `[DisallowNull]`.
 - **DO** add `[NotNullWhen(true)]` to nullable arguments of `Try` methods that will definitively be non-`null` if the method returns `true`.  For example, if `Int32.TryParse(string? s)` returns `true`, `s` is known to not be `null`, and so the method should be `public static bool TryParse([NotNullWhen(true)] string? s, out int result)`.
+- **DO** add `[NotNullWhen(true)]` to overrides of `public virtual bool Equals(object? obj)`, except in the extremely rare circumstance where a non-null instance may compare equally to `null` (one example of where it's not valid is on `Nullable<T>`).
 - **DO** add `[NotNullIfNotNull(string)]` if nullable ref argument will be non-`null` upon exit, when an other argument passed evaluated to non-`null`, pass that argument name as string. Example: `public void Exchange([NotNullIfNotNull("value")] ref object? location, object? value);`.
 - **DO** add `[return: NotNullIfNotNull(string)]` if a method would not return `null` in case an argument passed evaluated to non-`null`, pass that argument name as string. Example: `[return: NotNullIfNotNull("name")] public string? FormatName(string? name);`
 - **DO** add `[MemberNotNull(string fieldName)]` to a helper method which initializes member field(s), passing in the field name. Example: `[MemberNotNull("_buffer")] private void InitializeBuffer()`.  This will help to avoid spurious warnings at call sites that call the initialization method and then proceed to use the specified field.  Note that there are two constructors to `MemberNotNull`; one that takes a single `string`, and one that takes a `params string[]`.  When the number of fields initialized is small (e.g. <= 3), it's preferable to use multiple `[MemberNotNull(string)]` attributes on the method rather than one `[MemberNotNull(string, string, string, ...)]` attribute, as the latter is not CLS compliant and will likely require `#pragma warning disable` and `#pragma warning restore` around the line to suppress warnings.

src/coreclr/System.Private.CoreLib/src/System/Delegate.CoreCLR.cs

@@ -93,7 +93,7 @@ protected Delegate([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.Al
         }
 
 
-        public override bool Equals(object? obj)
+        public override bool Equals([NotNullWhen(true)] object? obj)
         {
             if (obj == null || !InternalEqualTypes(this, obj))
                 return false;

src/coreclr/System.Private.CoreLib/src/System/Diagnostics/SymbolStore/Token.cs

@@ -9,6 +9,8 @@
 **
 ===========================================================*/
 
+using System.Diagnostics.CodeAnalysis;
+
 namespace System.Diagnostics.SymbolStore
 {
     internal struct SymbolToken
@@ -21,7 +23,7 @@ internal struct SymbolToken
 
         public override int GetHashCode() { return m_token; }
 
-        public override bool Equals(object? obj)
+        public override bool Equals([NotNullWhen(true)] object? obj)
         {
             if (obj is SymbolToken)
                 return Equals((SymbolToken)obj);

src/coreclr/System.Private.CoreLib/src/System/Enum.CoreCLR.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
@@ -13,7 +14,7 @@ public abstract partial class Enum
         private static extern void GetEnumValuesAndNames(QCallTypeHandle enumType, ObjectHandleOnStack values, ObjectHandleOnStack names, Interop.BOOL getNames);
 
         [MethodImpl(MethodImplOptions.InternalCall)]
-        public extern override bool Equals(object? obj);
+        public extern override bool Equals([NotNullWhen(true)] object? obj);
 
         [MethodImpl(MethodImplOptions.InternalCall)]
         private static extern object InternalBoxEnum(RuntimeType enumType, long value);

src/coreclr/System.Private.CoreLib/src/System/MulticastDelegate.cs

@@ -54,7 +54,7 @@ public override void GetObjectData(SerializationInfo info, StreamingContext cont
 
         // equals returns true IIF the delegate is not null and has the
         //    same target, method and invocation list as this object
-        public sealed override bool Equals(object? obj)
+        public sealed override bool Equals([NotNullWhen(true)] object? obj)
         {
             if (obj == null)
                 return false;

src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs

@@ -1246,7 +1246,7 @@ public override int GetHashCode()
             return m_ptr != null ? m_ptr.GetHashCode() : 0;
         }
 
-        public override bool Equals(object? obj)
+        public override bool Equals([NotNullWhen(true)] object? obj)
         {
             if (!(obj is ModuleHandle))
                 return false;

src/coreclr/System.Private.CoreLib/src/System/ValueType.cs

@@ -22,7 +22,7 @@ public abstract class ValueType
     {
         [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2075:UnrecognizedReflectionPattern",
             Justification = "Trimmed fields don't make a difference for equality")]
-        public override bool Equals(object? obj)
+        public override bool Equals([NotNullWhen(true)] object? obj)
         {
             if (null == obj)
             {

src/libraries/System.Console/ref/System.Console.cs

@@ -310,7 +310,7 @@ public enum ConsoleKey
         public char KeyChar { get { throw null; } }
         public System.ConsoleModifiers Modifiers { get { throw null; } }
         public bool Equals(System.ConsoleKeyInfo obj) { throw null; }
-        public override bool Equals(object? value) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? value) { throw null; }
         public override int GetHashCode() { throw null; }
         public static bool operator ==(System.ConsoleKeyInfo a, System.ConsoleKeyInfo b) { throw null; }
         public static bool operator !=(System.ConsoleKeyInfo a, System.ConsoleKeyInfo b) { throw null; }

src/libraries/System.Console/src/System/ConsoleKeyInfo.cs

@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics.CodeAnalysis;
+
 namespace System
 {
     public readonly struct ConsoleKeyInfo : IEquatable<ConsoleKeyInfo>
@@ -46,7 +48,7 @@ public ConsoleModifiers Modifiers
             get { return _mods; }
         }
 
-        public override bool Equals(object? value)
+        public override bool Equals([NotNullWhen(true)] object? value)
         {
             return value is ConsoleKeyInfo info && Equals(info);
         }

src/libraries/System.Diagnostics.DiagnosticSource/ref/System.Diagnostics.DiagnosticSourceActivity.cs

@@ -132,7 +132,7 @@ public void CopyTo(System.Span<byte> destination) { }
         public static System.Diagnostics.ActivitySpanId CreateFromUtf8String(System.ReadOnlySpan<byte> idData) { throw null; }
         public static System.Diagnostics.ActivitySpanId CreateRandom() { throw null; }
         public bool Equals(System.Diagnostics.ActivitySpanId spanId) { throw null; }
-        public override bool Equals(object? obj) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? obj) { throw null; }
         public override int GetHashCode() { throw null; }
         public static bool operator ==(System.Diagnostics.ActivitySpanId spanId1, System.Diagnostics.ActivitySpanId spandId2) { throw null; }
         public static bool operator !=(System.Diagnostics.ActivitySpanId spanId1, System.Diagnostics.ActivitySpanId spandId2) { throw null; }
@@ -171,7 +171,7 @@ public void CopyTo(System.Span<byte> destination) { }
         public static System.Diagnostics.ActivityTraceId CreateFromUtf8String(System.ReadOnlySpan<byte> idData) { throw null; }
         public static System.Diagnostics.ActivityTraceId CreateRandom() { throw null; }
         public bool Equals(System.Diagnostics.ActivityTraceId traceId) { throw null; }
-        public override bool Equals(object? obj) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? obj) { throw null; }
         public override int GetHashCode() { throw null; }
         public static bool operator ==(System.Diagnostics.ActivityTraceId traceId1, System.Diagnostics.ActivityTraceId traceId2) { throw null; }
         public static bool operator !=(System.Diagnostics.ActivityTraceId traceId1, System.Diagnostics.ActivityTraceId traceId2) { throw null; }
@@ -227,15 +227,15 @@ public readonly struct ActivityEvent
         public static bool operator ==(System.Diagnostics.ActivityContext left, System.Diagnostics.ActivityContext right) { throw null; }
         public static bool operator !=(System.Diagnostics.ActivityContext left, System.Diagnostics.ActivityContext right) { throw null; }
         public bool Equals(System.Diagnostics.ActivityContext value) { throw null; }
-        public override bool Equals(object? obj) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? obj) { throw null; }
         public override int GetHashCode() { throw null; }
     }
     public readonly struct ActivityLink : IEquatable<ActivityLink>
     {
         public ActivityLink(System.Diagnostics.ActivityContext context, System.Diagnostics.ActivityTagsCollection? tags = null) { throw null; }
         public System.Diagnostics.ActivityContext Context  { get { throw null; } }
         public System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>>? Tags  { get { throw null; } }
-        public override bool Equals(object? obj) { throw null; }
+        public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] object? obj) { throw null; }
         public bool Equals(System.Diagnostics.ActivityLink value) { throw null; }
         public static bool operator ==(System.Diagnostics.ActivityLink left, System.Diagnostics.ActivityLink right) { throw null; }
         public static bool operator !=(System.Diagnostics.ActivityLink left, System.Diagnostics.ActivityLink right) { throw null; }