Addressed PR feedback.

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_ILockStatement.cs

@@ -449,7 +449,7 @@ void M(object source1, object source2, object source3)
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                       IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: lockTaken) (OperationKind.Argument, Type: null, IsImplicit) (Syntax: 'source1 ?? source2')
-                        ILocalReferenceOperation:  (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsImplicit) (Syntax: 'source1 ?? source2')
+                        ILocalReferenceOperation:  (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsImplicit) (Syntax: 'source1 ?? source2')
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
 
@@ -652,7 +652,7 @@ void M(int input1, bool input2)
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                       IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: lockTaken) (OperationKind.Argument, Type: null, IsInvalid, IsImplicit) (Syntax: 'input1')
-                        ILocalReferenceOperation:  (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsInvalid, IsImplicit) (Syntax: 'input1')
+                        ILocalReferenceOperation:  (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsInvalid, IsImplicit) (Syntax: 'input1')
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
 
@@ -759,7 +759,7 @@ void M(bool input2)
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                       IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: lockTaken) (OperationKind.Argument, Type: null, IsImplicit) (Syntax: 'null')
-                        ILocalReferenceOperation:  (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsImplicit) (Syntax: 'null')
+                        ILocalReferenceOperation:  (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsImplicit) (Syntax: 'null')
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
 
@@ -948,7 +948,7 @@ void M(P input, bool b)
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                       IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: lockTaken) (OperationKind.Argument, Type: null, IsImplicit) (Syntax: 'input')
-                        ILocalReferenceOperation:  (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsImplicit) (Syntax: 'input')
+                        ILocalReferenceOperation:  (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsImplicit) (Syntax: 'input')
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
 

src/Compilers/Core/Portable/Operations/ControlFlowGraphBuilder.cs

@@ -3243,6 +3243,7 @@ public override IOperation VisitLock(ILockOperation operation, int? captureIdFor
             // For simplicity, we will not synthesize this call because its presence is unlikely to affect graph analysis.
 
             IOperation lockedValue = Visit(operation.LockedValue);
+            var baseLockStatement = (BaseLockStatement)operation;
 
             if (!objectType.Equals(lockedValue.Type))
             {
@@ -3258,6 +3259,7 @@ public override IOperation VisitLock(ILockOperation operation, int? captureIdFor
 
             if (legacyMode)
             {
+                Debug.Assert(baseLockStatement.LockTakenSymbol == null);
                 enterMethod = (IMethodSymbol)_compilation.CommonGetWellKnownTypeMember(WellKnownMember.System_Threading_Monitor__Enter);
 
                 // Monitor.Enter($lock);
@@ -3283,7 +3285,6 @@ public override IOperation VisitLock(ILockOperation operation, int? captureIdFor
             }
             else
             {
-                var baseLockStatement = (BaseLockStatement)operation;
                 EnterRegion(new RegionBuilder(ControlFlowRegionKind.LocalLifetime, locals: ImmutableArray.Create(baseLockStatement.LockTakenSymbol)));
             }
 
@@ -3296,8 +3297,7 @@ public override IOperation VisitLock(ILockOperation operation, int? captureIdFor
             if (!legacyMode)
             {
                 // Monitor.Enter($lock, ref $lockTaken);
-                var baseLockStatement = (BaseLockStatement)operation;
-                lockTaken = new LocalReferenceExpression(baseLockStatement.LockTakenSymbol, isDeclaration: false, semanticModel: null, lockedValue.Syntax,
+                lockTaken = new LocalReferenceExpression(baseLockStatement.LockTakenSymbol, isDeclaration: true, semanticModel: null, lockedValue.Syntax,
                                                          baseLockStatement.LockTakenSymbol.Type, constantValue: null, isImplicit: true);
                 AddStatement(new InvocationExpression(enterMethod, instance: null, isVirtual: false,
                                                       ImmutableArray.Create<IArgumentOperation>(
@@ -3337,7 +3337,8 @@ public override IOperation VisitLock(ILockOperation operation, int? captureIdFor
             if (!legacyMode)
             {
                 // if ($lockTaken)
-                IOperation condition = OperationCloner.CloneOperation(lockTaken);
+                IOperation condition = new LocalReferenceExpression(baseLockStatement.LockTakenSymbol, isDeclaration: false, semanticModel: null, lockedValue.Syntax,
+                                                                    baseLockStatement.LockTakenSymbol.Type, constantValue: null, isImplicit: true);
                 condition = Operation.SetParentOperation(condition, null);
                 LinkBlocks(CurrentBasicBlock, condition, jumpIfTrue: false, RegularBranch(endOfFinally));
                 _currentBasicBlock = null;

src/Compilers/VisualBasic/Test/IOperation/IOperation/IOperationTests_ILockStatement.vb

@@ -411,7 +411,7 @@ Block[B1] - Block
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                       IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: lockTaken) (OperationKind.Argument, Type: null, IsImplicit) (Syntax: 'Nothing')
-                        ILocalReferenceOperation:  (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsImplicit) (Syntax: 'Nothing')
+                        ILocalReferenceOperation:  (IsDeclaration: True) (OperationKind.LocalReference, Type: System.Boolean, Constant: null, IsImplicit) (Syntax: 'Nothing')
                         InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                         OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)