Remove warning for yield return in lock

docs/compilers/CSharp/Warnversion Warning Waves.md

@@ -13,14 +13,6 @@ In a typical project, this setting is controlled by the `AnalysisLevel` property
 which determines the `WarningLevel` property (passed to the `Csc` task).
 For more information on `AnalysisLevel`, see https://devblogs.microsoft.com/dotnet/automatically-find-latent-bugs-in-your-code-with-net-5/
 
-## Warning level 9
-
-The compiler shipped with .NET 9 (the C# 13 compiler) contains the following warnings which are reported only under `/warn:9` or higher.
-
-| Warning ID | Description |
-|------------|-------------|
-| CS9237 | ['yield return' should not be used in the body of a lock statement](https://github.com/dotnet/roslyn/issues/72443) |
-
 ## Warning level 8
 
 The compiler shipped with .NET 8 (the C# 12 compiler) contains the following warnings which are reported only under `/warn:8` or higher.

src/Compilers/CSharp/Portable/Binder/Binder_Statements.cs

@@ -270,11 +270,6 @@ private BoundStatement BindYieldReturnStatement(YieldStatementSyntax node, Bindi
             {
                 Error(diagnostics, ErrorCode.ERR_BadYieldInUnsafe, node.YieldKeyword);
             }
-            // NOTE: Error conditions should be checked above this point; only warning conditions below.
-            else if (this.Flags.Includes(BinderFlags.InLockBody))
-            {
-                Error(diagnostics, ErrorCode.WRN_BadYieldInLock, node.YieldKeyword);
-            }
 
             CheckRequiredLangVersionForIteratorMethods(node, diagnostics);
             return new BoundYieldReturnStatement(node, argument);

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -7899,12 +7899,6 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_InterceptsLocationDataInvalidPosition" xml:space="preserve">
     <value>The data argument to InterceptsLocationAttribute refers to an invalid position in file '{0}'.</value>
   </data>
-  <data name="WRN_BadYieldInLock" xml:space="preserve">
-    <value>'yield return' should not be used in the body of a lock statement</value>
-  </data>
-  <data name="WRN_BadYieldInLock_Title" xml:space="preserve">
-    <value>'yield return' should not be used in the body of a lock statement</value>
-  </data>
   <data name="IDS_FeatureRefUnsafeInIteratorAsync" xml:space="preserve">
     <value>ref and unsafe in async and iterator methods</value>
   </data>

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

@@ -2312,7 +2312,7 @@ internal enum ErrorCode
 
         #endregion
 
-        WRN_BadYieldInLock = 9237,
+        // available 9237
         ERR_BadYieldInUnsafe = 9238,
         ERR_AddressOfInIterator = 9239,
 

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

@@ -207,10 +207,6 @@ internal static int GetWarningLevel(ErrorCode code)
             // docs/compilers/CSharp/Warnversion Warning Waves.md
             switch (code)
             {
-                case ErrorCode.WRN_BadYieldInLock:
-                    // Warning level 9 is exclusively for warnings introduced in the compiler
-                    // shipped with dotnet 9 (C# 13) and that can be reported for pre-existing code.
-                    return 9;
                 case ErrorCode.WRN_AddressOfInAsync:
                 case ErrorCode.WRN_ByValArraySizeConstRequired:
                     // Warning level 8 is exclusively for warnings introduced in the compiler
@@ -2434,7 +2430,6 @@ or ErrorCode.ERR_InterceptsLocationDuplicateFile
                 or ErrorCode.ERR_InterceptsLocationFileNotFound
                 or ErrorCode.ERR_InterceptsLocationDataInvalidPosition
                 or ErrorCode.INF_TooManyBoundLambdas
-                or ErrorCode.WRN_BadYieldInLock
                 or ErrorCode.ERR_BadYieldInUnsafe
                 or ErrorCode.ERR_AddressOfInIterator
                 or ErrorCode.ERR_RuntimeDoesNotSupportByRefLikeGenerics

src/Compilers/CSharp/Test/Emit2/Emit/EditAndContinue/EditAndContinueStateMachineTests.cs

@@ -5463,10 +5463,7 @@ static IEnumerable<int> F()
             var compilation1 = compilation0.WithSource(source1.Tree);
 
             var v0 = CompileAndVerify(compilation0);
-            v0.VerifyDiagnostics(
-                // (17,34): warning CS9237: 'yield return' should not be used in the body of a lock statement
-                //                                  yield return 1;      
-                Diagnostic(ErrorCode.WRN_BadYieldInLock, "yield").WithLocation(17, 34));
+            v0.VerifyDiagnostics();
             var md0 = ModuleMetadata.CreateFromImage(v0.EmittedAssemblyData);
 
             var f0 = compilation0.GetMember<MethodSymbol>("C.F");

src/Compilers/CSharp/Test/Emit2/Semantics/LockTests.cs

@@ -3448,10 +3448,7 @@ IEnumerable<int> M()
         CreateCompilation([source, LockTypeDefinition]).VerifyEmitDiagnostics(
             // (9,15): error CS4007: Instance of type 'System.Threading.Lock.Scope' cannot be preserved across 'await' or 'yield' boundary.
             //         lock (new Lock())
-            Diagnostic(ErrorCode.ERR_ByRefTypeAndAwait, "new Lock()").WithArguments("System.Threading.Lock.Scope").WithLocation(9, 15),
-            // (11,13): warning CS9237: 'yield return' should not be used in the body of a lock statement
-            //             yield return 2;
-            Diagnostic(ErrorCode.WRN_BadYieldInLock, "yield").WithLocation(11, 13));
+            Diagnostic(ErrorCode.ERR_ByRefTypeAndAwait, "new Lock()").WithArguments("System.Threading.Lock.Scope").WithLocation(9, 15));
     }
 
     [Fact]
@@ -3560,10 +3557,7 @@ async IAsyncEnumerable<int> M()
         CreateCompilationWithTasksExtensions([source, LockTypeDefinition, AsyncStreamsTypes]).VerifyEmitDiagnostics(
             // (10,15): error CS4007: Instance of type 'System.Threading.Lock.Scope' cannot be preserved across 'await' or 'yield' boundary.
             //         lock (new Lock())
-            Diagnostic(ErrorCode.ERR_ByRefTypeAndAwait, "new Lock()").WithArguments("System.Threading.Lock.Scope").WithLocation(10, 15),
-            // (12,13): warning CS9237: 'yield return' should not be used in the body of a lock statement
-            //             yield return 2;
-            Diagnostic(ErrorCode.WRN_BadYieldInLock, "yield").WithLocation(12, 13));
+            Diagnostic(ErrorCode.ERR_ByRefTypeAndAwait, "new Lock()").WithArguments("System.Threading.Lock.Scope").WithLocation(10, 15));
     }
 
     [Fact]