Made IDE change very specific to the affected scenario

More CR feedback

src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Conversion.cs

@@ -618,7 +618,7 @@ private BoundExpression MakeImplicitConversion(BoundExpression rewrittenOperand,
                 tupleTypeSymbol = TupleTypeSymbol.Create((NamedTypeSymbol)srcType);
             }
 
-            var srcElementFields = ((TupleTypeSymbol)srcType).TupleDefaultElementFields;
+            var srcElementFields = tupleTypeSymbol.TupleDefaultElementFields;
             var fieldAccessorsBuilder = ArrayBuilder<BoundExpression>.GetInstance(numElements);
 
             BoundAssignmentOperator assignmentToTemp;

src/Compilers/CSharp/Portable/Symbols/Tuples/TupleTypeSymbol.cs

@@ -845,10 +845,10 @@ private ImmutableArray<Symbol> CreateMembers()
 
                                 if (defaultImplicitlyDeclared && providedName != null)
                                 {
-                                        // The name given doesn't match the default name Item8, etc.
-                                        // Add a virtual field with the given name
-                                        // tupleFieldIndex << 1 + 1, because this is not a default element
-                                        members.Add(new TupleVirtualElementFieldSymbol(this, fieldSymbol, providedName, (tupleFieldIndex << 1) + 1, location, isImplicitlyDeclared: false));
+                                    // The name given doesn't match the default name Item8, etc.
+                                    // Add a virtual field with the given name
+                                    // tupleFieldIndex << 1 + 1, because this is not a default element
+                                    members.Add(new TupleVirtualElementFieldSymbol(this, fieldSymbol, providedName, (tupleFieldIndex << 1) + 1, location, isImplicitlyDeclared: false));
                                 }
 
                                 elementsMatchedByFields[tupleFieldIndex] = true; // mark as handled
@@ -937,7 +937,7 @@ private ImmutableArray<Symbol> CreateMembers()
 
                     // Add default element field. 
                     // i << 1 because this is a default element
-                    members.Add(new TupleErrorFieldSymbol(this, defaultName, i << 1, defaultImplicitlyDeclared ? null: location, _elementTypes[i], diagnosticInfo, defaultImplicitlyDeclared));
+                    members.Add(new TupleErrorFieldSymbol(this, defaultName, i << 1, defaultImplicitlyDeclared ? null : location, _elementTypes[i], diagnosticInfo, defaultImplicitlyDeclared));
 
 
                     if (defaultImplicitlyDeclared && providedName != null)

src/Compilers/VisualBasic/Portable/Symbols/Tuples/TupleErrorFieldSymbol.vb

@@ -83,12 +83,12 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
             End Get
         End Property
 
-        Public Sub New(container As NamedTypeSymbol, name As String, tupleFieldId As Integer, location As Location, type As TypeSymbol, useSiteDiagnosticInfo As DiagnosticInfo, isImplicitlyDeclared As Boolean)
+        Public Sub New(container As NamedTypeSymbol, name As String, tupleElementIndex As Integer, location As Location, type As TypeSymbol, useSiteDiagnosticInfo As DiagnosticInfo, isImplicitlyDeclared As Boolean)
             MyBase.New(container, container, type, name, Accessibility.Public)
             Debug.Assert(name <> Nothing)
             Me._locations = If((location Is Nothing), ImmutableArray(Of Location).Empty, ImmutableArray.Create(Of Location)(location))
             Me._useSiteDiagnosticInfo = useSiteDiagnosticInfo
-            Me._tupleElementIndex = tupleFieldId
+            Me._tupleElementIndex = tupleElementIndex
             Me._isImplicitlyDeclared = isImplicitlyDeclared
         End Sub
 

src/Compilers/VisualBasic/Portable/Symbols/Tuples/TupleFieldSymbol.vb

@@ -175,8 +175,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
             End Get
         End Property
 
-        Public Sub New(container As TupleTypeSymbol, underlyingField As FieldSymbol, tupleFieldId As Integer, location As Location, isImplicitlyDeclared As Boolean)
-            MyBase.New(container, underlyingField, tupleFieldId)
+        Public Sub New(container As TupleTypeSymbol, underlyingField As FieldSymbol, tupleElementIndex As Integer, location As Location, isImplicitlyDeclared As Boolean)
+            MyBase.New(container, underlyingField, tupleElementIndex)
             Me._locations = If((location Is Nothing), ImmutableArray(Of Location).Empty, ImmutableArray.Create(Of Location)(location))
             Me._isImplicitlyDeclared = isImplicitlyDeclared
         End Sub

src/EditorFeatures/Core/Implementation/RenameTracking/RenameTrackingTaggerProvider.TrackingSession.cs

@@ -208,7 +208,16 @@ private async Task<TriggerIdentifierKind> DetermineIfRenamableSymbolAsync(ISymbo
                 // Get the source symbol if possible
                 var sourceSymbol = await SymbolFinder.FindSourceDefinitionAsync(symbol, document.Project.Solution, _cancellationToken).ConfigureAwait(false) ?? symbol;
 
-                if (sourceSymbol.IsImplicitlyDeclared || !sourceSymbol.Locations.All(loc => loc.IsInSource))
+                if (sourceSymbol.Kind == SymbolKind.Field && 
+                    ((IFieldSymbol)sourceSymbol).ContainingType.IsTupleType &&
+                    sourceSymbol.IsImplicitlyDeclared)
+                {
+                    // should not rename Item1, Item2...
+                    // when user did not declare them in source.
+                    return TriggerIdentifierKind.NotRenamable;
+                }
+
+                if (!sourceSymbol.Locations.All(loc => loc.IsInSource))
                 {
                     return TriggerIdentifierKind.NotRenamable;
                 }