Suppress refactoring if writing outside loop.

src/EditorFeatures/VisualBasicTest/ConvertForToForEach/ConvertForToForEachTests.vb

@@ -70,6 +70,21 @@ class C
 end class")
         End Function
 
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsConvertForToForEach)>
+        Public Async Function TestMissingIfReferencingNotDeclaringVariable() As Task
+            Await TestMissingInRegularAndScriptAsync(
+"imports System
+
+class C
+    sub Test(array as string())
+        dim i as integer
+        [||]For i = 0 to array.Length - 1 step 2
+            Console.WriteLine(array(i))
+        next
+    end sub
+end class")
+        End Function
+
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsConvertForToForEach)>
         Public Async Function TestMissingWithIncorrectCondition1() As Task
             Await TestMissingInRegularAndScriptAsync(

src/Features/Core/Portable/ConvertForToForEach/AbstractConvertForToForEachCodeRefactoringProvider.cs

@@ -93,6 +93,20 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
 
             var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
+            // If the for-variable is an identifier, then make sure it's declaring a variable
+            // at the for-statemnet, and not referencing some previously declared symbol.  i.e
+            var iterationSymbol = semanticModel.GetSymbolInfo(iterationVariable.Parent, cancellationToken).GetAnySymbol();
+            if (iterationSymbol != null)
+            {
+                if (iterationSymbol.Locations.Length != 1 ||
+                    !iterationSymbol.Locations[0].IsInSource ||
+                    iterationVariable != iterationSymbol.Locations[0].FindToken(cancellationToken))
+                {
+                    // was a reference to some other variable.
+                    return;
+                }
+            }
+
             // Make sure we're starting at 0.
             var initializerValue = semanticModel.GetConstantValue(initializer, cancellationToken);
             if (!(initializerValue.HasValue && initializerValue.Value is 0))