Remove RequiresPreviewFeatures attribute on Lock, add test using the lock keyword (#102222)

- Also removed the `EnablePreviewFeatures` project properties that were added with `Lock` changes
- Added some basic tests with `Lock` using the `lock` keyword

Author: kouvel

src/coreclr/nativeaot/System.Private.DisabledReflection/src/System.Private.DisabledReflection.csproj

@@ -2,8 +2,6 @@
   <PropertyGroup>
     <!-- we access a lot of internals of System.Private.CoreLib, disable compiling against the ref assembly for now so we don't need to update it -->
     <CompileUsingReferenceAssemblies>false</CompileUsingReferenceAssemblies>
-    <!-- CA2252: Opt in to preview features before using them (Lock) -->
-    <EnablePreviewFeatures>true</EnablePreviewFeatures>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\System.Private.CoreLib\src\System.Private.CoreLib.csproj" />

src/coreclr/nativeaot/System.Private.Reflection.Execution/src/System.Private.Reflection.Execution.csproj

@@ -8,8 +8,6 @@
     <NativeFormatCommonPath>$(CompilerCommonPath)\Internal\NativeFormat</NativeFormatCommonPath>
     <!-- we access a lot of internals of System.Private.CoreLib, disable compiling against the ref assembly for now so we don't need to update it -->
     <CompileUsingReferenceAssemblies>false</CompileUsingReferenceAssemblies>
-    <!-- CA2252: Opt in to preview features before using them (Lock) -->
-    <EnablePreviewFeatures>true</EnablePreviewFeatures>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="$(NativeFormatCommonPath)\NativeFormat.cs" />

src/coreclr/nativeaot/System.Private.StackTraceMetadata/src/System.Private.StackTraceMetadata.csproj

@@ -2,8 +2,6 @@
   <PropertyGroup>
     <!-- we access a lot of internals of System.Private.CoreLib, disable compiling against the ref assembly for now so we don't need to update it -->
     <CompileUsingReferenceAssemblies>false</CompileUsingReferenceAssemblies>
-    <!-- CA2252: Opt in to preview features before using them (Lock) -->
-    <EnablePreviewFeatures>true</EnablePreviewFeatures>
   </PropertyGroup>
 
   <ItemGroup>

src/coreclr/nativeaot/System.Private.TypeLoader/src/System.Private.TypeLoader.csproj

@@ -8,8 +8,6 @@
     <DefineConstants Condition="'$(GENERICS_FORCE_USG)' != ''">GENERICS_FORCE_USG;$(DefineConstants)</DefineConstants>
     <!-- we access a lot of internals of System.Private.CoreLib, disable compiling against the ref assembly for now so we don't need to update it -->
     <CompileUsingReferenceAssemblies>false</CompileUsingReferenceAssemblies>
-    <!-- CA2252: Opt in to preview features before using them (Lock) -->
-    <EnablePreviewFeatures>true</EnablePreviewFeatures>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\System.Private.CoreLib\src\System.Private.CoreLib.csproj" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -4,8 +4,6 @@
     <SharedGUID>c5ed3c1d-b572-46f1-8f96-522a85ce1179</SharedGUID>
     <StringResourcesName Condition="'$(StringResourcesName)' == ''">System.Private.CoreLib.Strings</StringResourcesName>
     <GenerateResourcesSubstitutions>true</GenerateResourcesSubstitutions>
-    <!-- CA2252: Opt in to preview features before using them (for System.Threading.Lock) -->
-    <EnablePreviewFeatures>true</EnablePreviewFeatures>
   </PropertyGroup>
   <PropertyGroup Label="Configuration">
     <Import_RootNamespace />

src/libraries/System.Private.CoreLib/src/System/Threading/Lock.cs

@@ -16,7 +16,6 @@ namespace System.Threading
     /// that holds a lock may enter the lock repeatedly without exiting it, such as recursively, in which case the thread should
     /// eventually exit the lock the same number of times to fully exit the lock and allow other threads to enter the lock.
     /// </remarks>
-    [Runtime.Versioning.RequiresPreviewFeatures]
     public sealed partial class Lock
     {
         private const short DefaultMaxSpinCount = 22;

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -15164,7 +15164,6 @@ public enum LazyThreadSafetyMode
         PublicationOnly = 1,
         ExecutionAndPublication = 2,
     }
-    [System.Runtime.Versioning.RequiresPreviewFeaturesAttribute]
     public sealed partial class Lock
     {
         public Lock() { }

src/libraries/System.Threading/tests/LockTests.cs

@@ -11,6 +11,37 @@ public static class LockTests
     {
         private const int FailTimeoutMilliseconds = 30000;
 
+#pragma warning disable CS9216 // casting Lock to object
+        [Fact]
+        public static void LockStatementWithLockVsMonitor()
+        {
+            Lock lockObj = new();
+            lock (lockObj)
+            {
+                Assert.True(lockObj.IsHeldByCurrentThread);
+                Assert.False(Monitor.IsEntered(lockObj));
+            }
+
+            lock ((object)lockObj)
+            {
+                Assert.False(lockObj.IsHeldByCurrentThread);
+                Assert.True(Monitor.IsEntered(lockObj));
+            }
+
+            LockOnTWhereTIsLock(lockObj);
+
+            static void LockOnTWhereTIsLock<T>(T lockObj) where T : class
+            {
+                Assert.IsType<Lock>(lockObj);
+                lock (lockObj)
+                {
+                    Assert.False(((Lock)(object)lockObj).IsHeldByCurrentThread);
+                    Assert.True(Monitor.IsEntered(lockObj));
+                }
+            }
+        }
+#pragma warning restore CS9216
+
         // Attempts a single recursive acquisition/release cycle of a newly-created lock.
         [Fact]
         public static void BasicRecursion()
@@ -27,6 +58,10 @@ public static void BasicRecursion()
             {
                 Assert.True(lockObj.IsHeldByCurrentThread);
             }
+            lock (lockObj)
+            {
+                Assert.True(lockObj.IsHeldByCurrentThread);
+            }
             Assert.True(lockObj.IsHeldByCurrentThread);
             lockObj.Exit();
             Assert.False(lockObj.IsHeldByCurrentThread);
@@ -64,6 +99,10 @@ public static void IsHeldByCurrentThread()
             {
                 Assert.True(lockObj.IsHeldByCurrentThread);
             }
+            lock (lockObj)
+            {
+                Assert.True(lockObj.IsHeldByCurrentThread);
+            }
             Assert.False(lockObj.IsHeldByCurrentThread);
         }
 

src/libraries/System.Threading/tests/System.Threading.Tests.csproj

@@ -4,8 +4,6 @@
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <!-- CA2252: Opt in to preview features before using them (Lock) -->
-    <EnablePreviewFeatures>true</EnablePreviewFeatures>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetOS)' == 'browser'">
     <XunitShowProgress>true</XunitShowProgress>