Rename IsCallsiteError to IsCallsiteTodo and document Parameter properties

src/EditorFeatures/CSharpTest/ChangeSignature/RemoveParametersTests.cs

@@ -333,7 +333,7 @@ void M()
             var updatedSignature = new[] {
                 new AddedParameterOrExistingIndex(0),
                 new AddedParameterOrExistingIndex(2),
-                new AddedParameterOrExistingIndex(new AddedParameter(null, "int", "newIntegerParameter", callSiteValue:"123", true, isCallsiteOmitted:false, isCallsiteError: false), "int") };
+                new AddedParameterOrExistingIndex(new AddedParameter(null, "int", "newIntegerParameter", callSiteValue:"123", true, isCallsiteOmitted:false, isCallsiteTodo: false), "int") };
 
             using var testState = ChangeSignatureTestState.Create(XElement.Parse(workspaceXml));
             testState.TestChangeSignatureOptionsService.UpdatedSignature = updatedSignature;

src/EditorFeatures/TestUtilities/ChangeSignature/AddedParameterOrExistingIndex.cs

@@ -44,7 +44,7 @@ public AddedParameterOrExistingIndex(AddedParameter addedParameterWithoutTypeSym
             string defaultValue = "",
             bool useNamedArguments = false,
             bool isCallsiteOmitted = false,
-            bool isCallsiteError = false,
+            bool isCallsiteTodo = false,
             bool typeBinds = true)
         {
             var parameter = new AddedParameter(
@@ -56,7 +56,7 @@ public AddedParameterOrExistingIndex(AddedParameter addedParameterWithoutTypeSym
                 defaultValue,
                 useNamedArguments,
                 isCallsiteOmitted,
-                isCallsiteError,
+                isCallsiteTodo,
                 typeBinds);
 
             return new AddedParameterOrExistingIndex(parameter, fullTypeName);
@@ -90,7 +90,7 @@ internal AddedParameter GetAddedParameter(Document document)
                 _addedParameterWithoutTypeSymbol.DefaultValue,
                 _addedParameterWithoutTypeSymbol.UseNamedArguments,
                 _addedParameterWithoutTypeSymbol.IsCallsiteOmitted,
-                _addedParameterWithoutTypeSymbol.IsCallsiteError);
+                _addedParameterWithoutTypeSymbol.IsCallsiteTodo);
         }
     }
 }

src/Features/Core/Portable/ChangeSignature/AbstractChangeSignatureService.cs

@@ -789,7 +789,7 @@ protected static int GetParameterIndex<TNode>(SeparatedSyntaxList<TNode> paramet
                             !SupportsOptionalAndParamsArrayParametersSimultaneously();
 
                         var isCallsiteActuallyOmitted = addedParameter.IsCallsiteOmitted && !forcedCallsiteErrorDueToParamsArray;
-                        var isCallsiteActuallyErrored = addedParameter.IsCallsiteError || forcedCallsiteErrorDueToParamsArray;
+                        var isCallsiteActuallyErrored = addedParameter.IsCallsiteTodo || forcedCallsiteErrorDueToParamsArray;
 
                         if (isCallsiteActuallyOmitted)
                         {

src/Features/Core/Portable/ChangeSignature/Parameter.cs

@@ -40,7 +40,7 @@ internal sealed class AddedParameter : Parameter
             string defaultValue = "",
             bool useNamedArguments = false,
             bool isCallsiteOmitted = false,
-            bool isCallsiteError = false,
+            bool isCallsiteTodo = false,
             bool typeBinds = true)
         {
             Type = type;
@@ -51,11 +51,11 @@ internal sealed class AddedParameter : Parameter
 
             IsRequired = isRequired;
             DefaultValue = defaultValue;
-            IsCallsiteError = isCallsiteError;
+            IsCallsiteTodo = isCallsiteTodo;
             IsCallsiteOmitted = isCallsiteOmitted;
             UseNamedArguments = useNamedArguments;
 
-            if (IsCallsiteError)
+            if (IsCallsiteTodo)
             {
                 CallSiteValue = FeaturesResources.ChangeSignature_NewParameterIntroduceTODOVariable;
             }
@@ -77,11 +77,37 @@ internal sealed class AddedParameter : Parameter
         public bool TypeBinds { get; }
         public string CallSiteValue { get; }
 
+        /// <summary>
+        /// True if required, false if optional with a default value.
+        /// </summary>
         public bool IsRequired { get; }
+
+        /// <summary>
+        /// Value to use in the declaration of an optional parameter.
+        /// E.g. the "3" in M(int x = 3);
+        /// </summary>
         public string DefaultValue { get; }
+
+        /// <summary>
+        /// When introducing an argument, this indicates whether it
+        /// should be named even if not required to be named. Often
+        /// useful for literal callsite values like "true" or "null".
+        /// </summary>
         public bool UseNamedArguments { get; }
+
+        /// <summary>
+        /// When an optional parameter is added, passing an argument for
+        /// it is not required. This indicates that the corresponding argument 
+        /// should be omitted. This often results in subsequent arguments needing
+        /// to become named arguments
+        /// </summary>
         public bool IsCallsiteOmitted { get; }
-        public bool IsCallsiteError { get; }
+
+        /// <summary>
+        /// Indicates whether a "TODO" should be introduced at callsites
+        /// to cause errors that the user can then go visit and fix up.
+        /// </summary>
+        public bool IsCallsiteTodo { get; }
 
         // For test purposes: to display assert failure details in tests.
         public override string ToString() => $"{Type.ToDisplayString(new SymbolDisplayFormat(genericsOptions: SymbolDisplayGenericsOptions.IncludeTypeParameters))} {Name} ({CallSiteValue})";

src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialog.xaml

@@ -115,7 +115,7 @@
                          Grid.Column="0" 
                          GroupName="CallsiteKind" 
                          VerticalContentAlignment="Center" 
-                         IsChecked="{Binding IsCallsiteError, Mode=TwoWay}"
+                         IsChecked="{Binding IsCallsiteTodo, Mode=TwoWay}"
                          Content="{Binding ElementName=dialog, Path=IntroduceUndefinedTodoVariables}"/>
             <RadioButton x:Name="OmitArgumentRadioButton" 
                          Grid.Row="11" 

src/VisualStudio/Core/Def/Implementation/ChangeSignature/AddParameterDialogViewModel.cs

@@ -110,7 +110,7 @@ public bool IsOptional
         }
 
         public string DefaultValue { get; set; }
-        public bool IsCallsiteError { get; set; }
+        public bool IsCallsiteTodo { get; set; }
         public bool IsCallsiteOmitted { get; set; }
         public bool IsCallsiteRegularValue { get; set; } = true;
 

src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureDialog.xaml.cs

@@ -144,7 +144,7 @@ private void Add_Click(object sender, RoutedEventArgs e)
                     addParameterViewModel.DefaultValue,
                     addParameterViewModel.UseNamedArguments,
                     addParameterViewModel.IsCallsiteOmitted,
-                    addParameterViewModel.IsCallsiteError,
+                    addParameterViewModel.IsCallsiteTodo,
                     addParameterViewModel.TypeBinds);
 
                 _viewModel.AddParameter(addedParameter);

src/VisualStudio/Core/Test/ChangeSignature/AddParameterViewModelTests.vb

@@ -273,7 +273,7 @@ class MyClass
             Assert.True(viewModel.IsCallsiteRegularValue)
             Assert.Equal(String.Empty, viewModel.CallSiteValue)
             Assert.False(viewModel.UseNamedArguments)
-            Assert.False(viewModel.IsCallsiteError)
+            Assert.False(viewModel.IsCallsiteTodo)
             Assert.False(viewModel.IsCallsiteOmitted)
 
             Assert.False(viewModel.TrySubmit)