Correctly detect option strict on/off when determining if cast is redundant

Fixes #3161 and Fixes #3163

User Scenario:
User has code with narrowing conversion with an explicit cast.  We will
offer to remove the cast even though this will cause the code to not
compile.

Fix Description:
We previously never consulted optionstrict to determine if a
user-defined narrowing cast was necessary.  The fix in CastAnalyzer.vb
will check if the conversion is narrowing, if option strict is on, or if
we generate a warning on implicit narrowing conversions.  We also offer
to add a cast if an implicit conversion warning is given.

Testing:  Added regression tests + existing tests

src/EditorFeatures/Test/Workspaces/TestWorkspaceFactory.cs

@@ -50,6 +50,7 @@ public partial class TestWorkspaceFactory
         private const string AnalyzerDisplayAttributeName = "Name";
         private const string AnalyzerFullPathAttributeName = "FullPath";
         private const string AliasAttributeName = "Alias";
+        private const string DiagnosticOptionElementName = "DiagnosticOption";
 
         /// <summary>
         /// Creates a single buffer in a workspace.

src/EditorFeatures/Test/Workspaces/TestWorkspaceFactory_XmlConsumption.cs

@@ -398,6 +398,7 @@ private static CompilationOptions CreateCompilationOptions(TestWorkspace workspa
             var rootNamespace = new VisualBasicCompilationOptions(OutputKind.ConsoleApplication).RootNamespace;
             var globalImports = new List<GlobalImport>();
             var reportDiagnostic = ReportDiagnostic.Default;
+            var specificDiagnostics = ImmutableDictionary.Create<string, ReportDiagnostic>();
 
             if (compilationOptionsElement != null)
             {
@@ -429,6 +430,10 @@ private static CompilationOptions CreateCompilationOptions(TestWorkspace workspa
                        : new VisualBasicCompilationOptions(OutputKind.WindowsRuntimeMetadata).WithGlobalImports(globalImports)
                                                                          .WithRootNamespace(rootNamespace);
                 }
+
+                specificDiagnostics = compilationOptionsElement.Elements(DiagnosticOptionElementName)
+                    .Select(x => KeyValuePair.Create(x.Value, (ReportDiagnostic)Enum.Parse(typeof(ReportDiagnostic), x.Attribute(ReportDiagnosticAttributeName).Value)))
+                    .ToImmutableDictionary();
             }
             else
             {
@@ -446,7 +451,8 @@ private static CompilationOptions CreateCompilationOptions(TestWorkspace workspa
                                                    .WithSourceReferenceResolver(SourceFileResolver.Default)
                                                    .WithXmlReferenceResolver(XmlFileResolver.Default)
                                                    .WithMetadataReferenceResolver(new AssemblyReferenceResolver(MetadataFileReferenceResolver.Default, MetadataFileReferenceProvider.Default))
-                                                   .WithAssemblyIdentityComparer(DesktopAssemblyIdentityComparer.Default);
+                                                   .WithAssemblyIdentityComparer(DesktopAssemblyIdentityComparer.Default)
+                                                   .WithSpecificDiagnosticOptions(specificDiagnostics);
 
             if (language == LanguageNames.VisualBasic)
             {

src/EditorFeatures/Test/Workspaces/TestWorkspaceFactory_XmlCreation.cs

@@ -75,6 +75,18 @@ private static XElement CreateCompilationOptionsElement(CompilationOptions optio
                     element.SetAttributeValue(RootNamespaceAttributeName, vbOptions.RootNamespace);
                 }
 
+                if (vbOptions.SpecificDiagnosticOptions?.Any() == true)
+                {
+                    element.Add(
+                    vbOptions.SpecificDiagnosticOptions.AsEnumerable().Select(
+                        i =>
+                        {
+                            var x = new XElement(DiagnosticOptionElementName, i.Key);
+                            x.SetAttributeValue(ReportDiagnosticAttributeName, System.Enum.GetName(typeof(ReportDiagnostic), i.Value));
+                            return x;
+                        }));
+                }
+
                 return element;
             }
 

src/EditorFeatures/VisualBasicTest/Diagnostics/AbstractVisualBasicDiagnosticProviderBasedUserDiagnosticTest.vb

@@ -32,11 +32,15 @@ Namespace Microsoft.CodeAnalysis.Editor.VisualBasic.UnitTests.Diagnostics
             Return input.Replace("\n", vbCrLf)
         End Function
 
-        Protected Overloads Sub Test(initialMarkup As XElement, expected As XElement, Optional index As Integer = 0, Optional compareTokens As Boolean = True)
+        Protected Overloads Sub Test(initialMarkup As XElement, expected As XElement, Optional index As Integer = 0, Optional compareTokens As Boolean = True, Optional compilationOptions As VisualBasicCompilationOptions = Nothing)
             Dim initialMarkupStr = initialMarkup.ConvertTestSourceTag()
             Dim expectedStr = expected.ConvertTestSourceTag()
 
-            MyBase.Test(initialMarkupStr, expectedStr, parseOptions:=Nothing, compilationOptions:=_compilationOptions, index:=index, compareTokens:=compareTokens)
+            If compilationOptions Is Nothing Then
+                compilationOptions = CType(_compilationOptions, VisualBasicCompilationOptions)
+            End If
+
+            MyBase.Test(initialMarkupStr, expectedStr, parseOptions:=Nothing, compilationOptions:=compilationOptions, index:=index, compareTokens:=compareTokens)
         End Sub
 
         Protected Overloads Sub TestMissingWithWorkspaceXml(initialMarkup As XElement)

src/EditorFeatures/VisualBasicTest/Diagnostics/InsertMissingCast/InsertMissingCastTests.vb

@@ -87,5 +87,12 @@ NewLines("Option Strict On \n Module Program \n Sub Main(args As String()) \n Di
             TestMissing(
 NewLines("Option Strict On \n Class A \n End Class \n Class B \n End Class \n Module Program[||] \n Sub Main(args As String()) \n Dim x As A = New B() \n End Sub \n End Module"))
         End Sub
+
+        <Fact(), Trait(Traits.Feature, Traits.Features.CodeActionsInsertMissingCast)>
+        Public Sub TestOptionStrictOn()
+            Test(
+NewLines("Option Strict On \n Module Module1 \n Sub Main() \n Dim red = ColorF.FromArgb(255, 255, 0, 0) \n Dim c As Color = [|red|] \n End Sub \n End Module \n Public Structure ColorF \n Public A, R, G, B As Single \n Public Shared Function FromArgb(a As Double, r As Double, g As Double, b As Double) As ColorF \n Return New ColorF With {.A = CSng(a), .R = CSng(r), .G = CSng(g), .B = CSng(b)} \n End Function \n Public Shared Widening Operator CType(x As Color) As ColorF \n Return ColorF.FromArgb(x.A / 255, x.R / 255, x.G / 255, x.B / 255) \n End Operator \n Public Shared Narrowing Operator CType(x As ColorF) As Color \n Return Color.FromArgb(CByte(x.A * 255), CByte(x.R * 255), CByte(x.G * 255), CByte(x.B * 255)) \n End Operator \n End Structure \n Public Structure Color \n Public A, R, G, B As Byte \n Public Shared Function FromArgb(a As Byte, r As Byte, g As Byte, b As Byte) As Color \n Return New Color With {.A = a, .R = r, .G = g, .B = b} \n End Function \n End Structure"),
+NewLines("Option Strict On \n Module Module1 \n Sub Main() \n Dim red = ColorF.FromArgb(255, 255, 0, 0) \n Dim c As Color = CType(red, Color) \n End Sub \n End Module \n Public Structure ColorF \n Public A, R, G, B As Single \n Public Shared Function FromArgb(a As Double, r As Double, g As Double, b As Double) As ColorF \n Return New ColorF With {.A = CSng(a), .R = CSng(r), .G = CSng(g), .B = CSng(b)} \n End Function \n Public Shared Widening Operator CType(x As Color) As ColorF \n Return ColorF.FromArgb(x.A / 255, x.R / 255, x.G / 255, x.B / 255) \n End Operator \n Public Shared Narrowing Operator CType(x As ColorF) As Color \n Return Color.FromArgb(CByte(x.A * 255), CByte(x.R * 255), CByte(x.G * 255), CByte(x.B * 255)) \n End Operator \n End Structure \n Public Structure Color \n Public A, R, G, B As Byte \n Public Shared Function FromArgb(a As Byte, r As Byte, g As Byte, b As Byte) As Color \n Return New Color With {.A = a, .R = r, .G = g, .B = b} \n End Function \n End Structure"))
+        End Sub
     End Class
 End Namespace

src/EditorFeatures/VisualBasicTest/Diagnostics/RemoveUnnecessaryCast/RemoveUnnecessaryCastTests.vb

@@ -2363,7 +2363,7 @@ End Class
         <WorkItem(544655)>
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)>
         Public Sub RemoveCastToICloneableForDelegate()
-            ' Note: The cast below can be removed because delegates are implictly sealed.
+            ' Note: The cast below can be removed because delegates are implicitly sealed.
 
             Dim markup =
 <File>
@@ -2396,7 +2396,7 @@ End Class
         <WorkItem(545926)>
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)>
         Public Sub RemoveCastToICloneableForArray()
-            ' Note: The cast below can be removed because arrays are implictly sealed.
+            ' Note: The cast below can be removed because arrays are implicitly sealed.
 
             Dim markup =
 <File>
@@ -2427,7 +2427,7 @@ End Class
         <WorkItem(529937)>
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)>
         Public Sub RemoveCastToICloneableForArray2()
-            ' Note: The cast below can be removed because arrays are implictly sealed.
+            ' Note: The cast below can be removed because arrays are implicitly sealed.
 
             Dim markup =
 <File>
@@ -2456,7 +2456,7 @@ End Module
         <WorkItem(529897)>
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)>
         Public Sub RemoveCastToIConvertibleForEnum()
-            ' Note: The cast below can be removed because enums are implictly sealed.
+            ' Note: The cast below can be removed because enums are implicitly sealed.
 
             Dim markup =
 <File>
@@ -2694,5 +2694,157 @@ End Class
 </File>
             TestMissing(markup)
         End Sub
+
+        <WorkItem(3163, "https://github.com/dotnet/roslyn/issues/3163")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)>
+        Public Sub DoNotRemoveCastInNarrowingConverionWihtOptionStrictOn()
+            Dim markup =
+<File>
+Option Strict On
+
+Module Module1
+
+    Sub Main()
+        Dim red = ColorF.FromArgb(255, 255, 0, 0)
+        Dim c As Color = [|CType(red, Color)|]
+    End Sub
+
+End Module
+
+Public Structure ColorF
+    Public A, R, G, B As Single
+    Public Shared Function FromArgb(a As Double, r As Double, g As Double, b As Double) As ColorF
+        Return New ColorF With {.A = CSng(a), .R = CSng(r), .G = CSng(g), .B = CSng(b)}
+    End Function
+    Public Shared Widening Operator CType(x As Color) As ColorF
+        Return ColorF.FromArgb(x.A / 255, x.R / 255, x.G / 255, x.B / 255)
+    End Operator
+    Public Shared Narrowing Operator CType(x As ColorF) As Color
+        Return Color.FromArgb(CByte(x.A * 255), CByte(x.R * 255), CByte(x.G * 255), CByte(x.B * 255))
+    End Operator
+End Structure
+
+Public Structure Color
+    Public A, R, G, B As Byte
+    Public Shared Function FromArgb(a As Byte, r As Byte, g As Byte, b As Byte) As Color
+        Return New Color With {.A = a, .R = r, .G = g, .B = b}
+    End Function
+End Structure
+</File>
+            TestMissing(markup)
+        End Sub
+
+        <WorkItem(3163, "https://github.com/dotnet/roslyn/issues/3163")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)>
+        Public Sub DoNotRemoveCastInNarrowingConverionWihtOptionStrictOffBC42016AsWarning()
+            Dim markup =
+<File>
+Option Strict Off
+
+Module Module1
+
+    Sub Main()
+        Dim red = ColorF.FromArgb(255, 255, 0, 0)
+        Dim c As Color = [|CType(red, Color)|]
+    End Sub
+
+End Module
+
+Public Structure ColorF
+    Public A, R, G, B As Single
+    Public Shared Function FromArgb(a As Double, r As Double, g As Double, b As Double) As ColorF
+        Return New ColorF With {.A = CSng(a), .R = CSng(r), .G = CSng(g), .B = CSng(b)}
+    End Function
+    Public Shared Widening Operator CType(x As Color) As ColorF
+        Return ColorF.FromArgb(x.A / 255, x.R / 255, x.G / 255, x.B / 255)
+    End Operator
+    Public Shared Narrowing Operator CType(x As ColorF) As Color
+        Return Color.FromArgb(CByte(x.A * 255), CByte(x.R * 255), CByte(x.G * 255), CByte(x.B * 255))
+    End Operator
+End Structure
+
+Public Structure Color
+    Public A, R, G, B As Byte
+    Public Shared Function FromArgb(a As Byte, r As Byte, g As Byte, b As Byte) As Color
+        Return New Color With {.A = a, .R = r, .G = g, .B = b}
+    End Function
+End Structure
+</File>
+            TestMissing(markup)
+        End Sub
+
+        <WorkItem(3163, "https://github.com/dotnet/roslyn/issues/3163")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)>
+        Public Sub RemoveCastInNarrowingConverionWihtOptionStrictOffBC42016Suppressed()
+            Dim markup =
+<File>
+Option Strict Off
+
+Module Module1
+
+    Sub Main()
+        Dim red = ColorF.FromArgb(255, 255, 0, 0)
+        Dim c As Color = [|CType(red, Color)|]
+    End Sub
+
+End Module
+
+Public Structure ColorF
+    Public A, R, G, B As Single
+    Public Shared Function FromArgb(a As Double, r As Double, g As Double, b As Double) As ColorF
+        Return New ColorF With {.A = CSng(a), .R = CSng(r), .G = CSng(g), .B = CSng(b)}
+    End Function
+    Public Shared Widening Operator CType(x As Color) As ColorF
+        Return ColorF.FromArgb(x.A / 255, x.R / 255, x.G / 255, x.B / 255)
+    End Operator
+    Public Shared Narrowing Operator CType(x As ColorF) As Color
+        Return Color.FromArgb(CByte(x.A * 255), CByte(x.R * 255), CByte(x.G * 255), CByte(x.B * 255))
+    End Operator
+End Structure
+
+Public Structure Color
+    Public A, R, G, B As Byte
+    Public Shared Function FromArgb(a As Byte, r As Byte, g As Byte, b As Byte) As Color
+        Return New Color With {.A = a, .R = r, .G = g, .B = b}
+    End Function
+End Structure
+</File>
+            Dim expected =
+<File>
+Option Strict Off
+
+Module Module1
+
+    Sub Main()
+        Dim red = ColorF.FromArgb(255, 255, 0, 0)
+        Dim c As Color = red
+    End Sub
+
+End Module
+
+Public Structure ColorF
+    Public A, R, G, B As Single
+    Public Shared Function FromArgb(a As Double, r As Double, g As Double, b As Double) As ColorF
+        Return New ColorF With {.A = CSng(a), .R = CSng(r), .G = CSng(g), .B = CSng(b)}
+    End Function
+    Public Shared Widening Operator CType(x As Color) As ColorF
+        Return ColorF.FromArgb(x.A / 255, x.R / 255, x.G / 255, x.B / 255)
+    End Operator
+    Public Shared Narrowing Operator CType(x As ColorF) As Color
+        Return Color.FromArgb(CByte(x.A * 255), CByte(x.R * 255), CByte(x.G * 255), CByte(x.B * 255))
+    End Operator
+End Structure
+
+Public Structure Color
+    Public A, R, G, B As Byte
+    Public Shared Function FromArgb(a As Byte, r As Byte, g As Byte, b As Byte) As Color
+        Return New Color With {.A = a, .R = r, .G = g, .B = b}
+    End Function
+End Structure
+</File>
+            Dim compilationOptions = New VisualBasicCompilationOptions(OutputKind.ConsoleApplication).WithOptionInfer(True)
+            compilationOptions = compilationOptions.WithSpecificDiagnosticOptions(compilationOptions.SpecificDiagnosticOptions.Add("BC42016", ReportDiagnostic.Suppress))
+            Test(markup, expected, compareTokens:=False, compilationOptions:=compilationOptions)
+        End Sub
     End Class
 End Namespace

src/Features/VisualBasic/CodeFixes/InsertMissingCast/InsertMissingCastCodeFixProvider.vb

@@ -12,10 +12,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeFixes.InsertMissingCast
         Inherits CodeFixProvider
 
         Friend Const BC30512 As String = "BC30512" ' Option Strict On disallows implicit conversions from '{0}' to '{1}'.
+        Friend Const BC42016 As String = "BC42016" ' Implicit conversions from '{0}' to '{1}'.
 
         Public NotOverridable Overrides ReadOnly Property FixableDiagnosticIds As ImmutableArray(Of String)
             Get
-                Return ImmutableArray.Create(BC30512)
+                Return ImmutableArray.Create(BC30512, BC42016)
             End Get
         End Property
 

src/Workspaces/VisualBasic/Portable/Extensions/CastAnalyzer.vb

@@ -253,7 +253,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Extensions
                 If castToOuterType.IsUserDefined OrElse expressionToCastType.IsUserDefined Then
                     Return (HaveSameUserDefinedConversion(expressionToCastType, expressionToOuterType) OrElse
                             HaveSameUserDefinedConversion(castToOuterType, expressionToOuterType)) AndAlso
-                           UserDefinedConversionIsAllowed(_castNode, _semanticModel)
+                           (UserDefinedConversionIsAllowed(_castNode, _semanticModel) AndAlso
+                            NarrowingConversionIsAllowed(expressionToCastType, _semanticModel))
                 ElseIf expressionToOuterType.IsUserDefined Then
                     Return False
                 End If
@@ -342,6 +343,28 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Extensions
             Return True
         End Function
 
+        Private Shared Function NarrowingConversionIsAllowed(conversion As Conversion, semanticModel As SemanticModel) As Boolean
+            ' If this is not a narrowing conversion then no VB compiler options will disallow it
+            If conversion.IsNarrowing Then
+                ' If Option Strict is On then all narrowing conversions are illegal
+                If semanticModel.OptionStrict = OptionStrict.On Then
+                    Return False
+                Else
+                    ' For all other cases we only want to label a cast as unnecessary if BC42016 is suppressed, 
+                    ' otherwise removing the cast will cause a warning or error to be shown to the user.
+                    Dim reportDiagnostic As ReportDiagnostic
+                    If semanticModel.Compilation.Options.SpecificDiagnosticOptions.TryGetValue("BC42016", reportDiagnostic) AndAlso
+                       reportDiagnostic = ReportDiagnostic.Suppress Then
+                        Return True
+                    Else
+                        Return False
+                    End If
+                End If
+            End If
+
+            Return True
+        End Function
+
         Private Shared Function IsRequiredWideningNumericConversion(sourceType As ITypeSymbol, destinationType As ITypeSymbol) As Boolean
             ' VB Language Specification: Section 8.3 Numeric Conversions