StructureAnalysisTests.vb

' Licensed to the .NET Foundation under one or more agreements.
' The .NET Foundation licenses this file to you under the MIT license.
' See the LICENSE file in the project root for more information.
 
Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Xml.Linq
Imports Microsoft.CodeAnalysis.Text
Imports Microsoft.CodeAnalysis.VisualBasic.Symbols
Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
Imports Roslyn.Test.Utilities
Imports Xunit
 
Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests
    Public Class StructureAnalysisTests
        Inherits FlowTestBase
 
        <Fact>
        Public Sub UnassignedFieldsInParameters()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="NestedStructs_NotAllFieldsReported">
          <file name="a.b">
Public Structure S
    Public Property P As Object
End Structure
Public Structure SS
    Public s As S
    Public s2 As S
    Public s3 As Object
    Public Sub F(p As SS)
        p.s.P = ""
    End Sub
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub NestedStructs_NotAllFieldsReported()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="NestedStructs_NotAllFieldsReported">
          <file name="a.b">
Public Structure S
    Public Property P As Object
End Structure
Public Structure SS
    Public s As S
    Public s2 As S
    Public s3 As Object
    Public Function F() As SS
        Dim ret As SS
        ret.s.P = Nothing
        ret.s2.P = Nothing
        Return ret
    End Function
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        ret.s.P = Nothing
        ~~~~~
BC42109: Variable 's2' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        ret.s2.P = Nothing
        ~~~~~~
BC42109: Variable 'ret' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        Return ret
               ~~~
</errors>)
        End Sub
 
        <Fact>
        Public Sub NestedStructs_AllFieldsReported()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="NestedStructs_AllFieldsReported">
          <file name="a.b">
Public Structure S
    Public Property P As Object
End Structure
Public Structure SS
    Public s As S
    Public s2 As S
    Public s3 As Object
    Public Function F() As SS
        Dim ret As SS
        ret.s.P = Nothing
        ret.s2.P = Nothing
        Dim o As Object = ret.s3
        Return ret
    End Function
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        ret.s.P = Nothing
        ~~~~~
BC42109: Variable 's2' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        ret.s2.P = Nothing
        ~~~~~~
BC42104: Variable 's3' is used before it has been assigned a value. A null reference exception could result at runtime.
        Dim o As Object = ret.s3
                          ~~~~~~
</errors>)
        End Sub
 
        <Fact>
        Public Sub BigStruct()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="BigStruct">
          <file name="a.b">
Public Structure S(Of T)
    Public a As T
    Public b As T
    Public c As T
    Public d As T
    Public e As T
    Public f As T
    Public g As T
    Public h As T
 
    Shared Sub M()
        Dim x As New S(Of S(Of S(Of S(Of S(Of S(Of S(Of S(Of Integer))))))))
        x.a.a.a.a.a.a.a.a = 12
        x.a.a.a.a.a.a.a.b = x.a.a.a.a.a.a.a.a
    End Sub
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub SimpleStructsWithGenerics()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="SimpleStructsWithGenerics">
          <file name="a.b">
Public Structure XXX
    Public x As S(Of Object)
    Public y As S(Of String)
End Structure
 
Public Structure S(Of T)
    Public a As String
    Public Property b As T
End Structure
 
Public Class Test
    Public Shared Sub Main(args As String())
        Dim s As XXX
        's.x.a = ""
        s.x.b = s.x.a
        Dim t As Object = s
    End Sub
    Public Shared Sub S1(ByRef arg As XXX)
        arg.x.a = ""
        arg.x.b = arg.x.a
    End Sub
End Class
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 'x' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        s.x.b = s.x.a
        ~~~
BC42104: Variable 'a' is used before it has been assigned a value. A null reference exception could result at runtime.
        s.x.b = s.x.a
                ~~~~~
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        Dim t As Object = s
                          ~
</errors>)
        End Sub
 
        <Fact>
        Public Sub CallingMethodsOnUninitializedStructs()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="CallingMethodsOnUninitializedStructs">
          <file name="a.b">
Public Structure XXX
    Public x As S(Of Object)
    Public y As S(Of String)
End Structure
 
Public Structure S(Of T)
    Public x As String
    Public Property y As T
End Structure
 
Public Class Test
    Public Shared Sub Main(args As String())
        Dim s As XXX
        s.x.y.ToString()
        Dim t As Object = s
    End Sub
    Public Shared Sub S1(ByRef arg As XXX)
        arg.x.x = ""
        arg.x.y = arg.x.x
    End Sub
End Class
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 'x' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        s.x.y.ToString()
        ~~~
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        Dim t As Object = s
                          ~
</errors>)
        End Sub
 
        <Fact>
        Public Sub CallingMethodsOnUninitializedStructs2()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="CallingMethodsOnUninitializedStructs2">
          <file name="a.b">
Public Structure XXX
    Public x As S(Of Object)
    Public y As S(Of String)
End Structure
 
Public Structure S(Of T)
    Public x As String
    Public Property y As T
End Structure
 
Public Class Test
    Public Shared Sub Main(args As String())
        Dim s As XXX
        s.x = New S(Of Object)()
        s.x.y.ToString()
        Dim t As Object = s
    End Sub
    Public Shared Sub S1(ByRef arg As XXX)
        arg.x.x = ""
        arg.x.y = arg.x.x
    End Sub
End Class
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        Dim t As Object = s
                          ~
</errors>)
        End Sub
 
        <Fact>
        Public Sub ReferencingCycledStructures()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40AndReferences(
<compilation name="Compilation">
    <file name="a.vb">
Class C
    Shared Sub Main()
        Dim s1 As S1 = New S1()
        Dim s2 As S2 = New S2()
        s2.fld = New S3()
        s2.fld.fld.fld.fld = New S2()
    End Sub
End Class
    </file>
</compilation>, {TestReferences.SymbolsTests.CycledStructs})
 
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
</errors>)
 
        End Sub
 
        <WorkItem(530076, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/530076")>
        <Fact>
        Public Sub Bug530076a()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40AndReferences(
<compilation name="Compilation">
    <file name="a.vb">
Imports System
 
Friend class RetVarWarn005mod
    Structure structTemp
        Public strTemp1 As String
        Public strTemp2 As String
    End Structure
    Function Sce1() As structTemp
        Sce1.strTemp1 = "Scenario1Temp1"
        Sce1.strTemp2 = "Scenario1Temp2"
    End Function
End class
    </file>
</compilation>, {})
 
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
</errors>)
 
        End Sub
 
        <WorkItem(530076, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/530076")>
        <Fact>
        Public Sub Bug530076b()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40AndReferences(
<compilation name="Compilation">
    <file name="a.vb">
Imports System
 
Friend class RetVarWarn005mod
    Structure structTemp
        Public strTemp1 As String
        Public strTemp2 As String
    End Structure
    Function Sce1() As structTemp
        dim Sce0 as structTemp
        Sce0.strTemp1 = "Scenario1Temp1"
        Sce0.strTemp2 = "Scenario1Temp2"
        Return Sce0 
    End Function
End class
    </file>
</compilation>, {})
 
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
</errors>)
        End Sub
 
        <WorkItem(807595, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/807595")>
        <Fact>
        Public Sub Bug807595()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40AndReferences(
<compilation name="Compilation">
    <file name="a.vb">
Imports System
 
Friend class RetVarWarn005mod
    Structure structTemp
        Public strTemp1 As String
        Public strTemp2 As String
    End Structure
    Function Sce1() As structTemp
        Dim Sce2 As structTemp
        Try
            Sce1.strTemp1 = "Scenario1Temp1InTry"
            Sce2.strTemp1 = "Scenario1Temp1InTry"
        Finally
            Sce1.strTemp2 = "Scenario1Temp2InFinally"
            Sce2.strTemp2 = "Scenario1Temp2InFinally"
        End Try
        Dim sce3 = Sce2
    End Function
End class
    </file>
</compilation>, {})
 
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
</errors>)
 
        End Sub
 
#Region "Test ported from C# + variations and derived tests"
 
        <Fact>
        Public Sub AllPiecesAssigned()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="AllPiecesAssigned">
          <file name="a.b">
        Public Structure S
            Public x As Integer
            Public y As Integer
        End Structure
 
        Public Class Test
            Public Shared Sub Main()
                Dim s As S
                s.x = 1
                s.y = 2
                Dim t As S = s
            End Sub
        End Class
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <WorkItem(542579, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/542579")>
        <Fact>
        Public Sub AllPiecesAssigned2()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40AndVBRuntime(
      <compilation name="AllPiecesAssigned2">
          <file name="a.b">
            Structure S
                Dim x As String
            End Structure
            Module Program
                Sub Main(args As String())
                    Dim S1 As S
                    S1.x = ""
                    Dim S2 = S1
                End Sub
            End Module
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <WorkItem(542579, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/542579")>
        <Fact>
        Public Sub AllPiecesAssigned3()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40AndVBRuntime(
      <compilation name="AllPiecesAssigned3">
          <file name="a.b">
            Structure S
                Dim x As String
            End Structure
            Module Program
                Sub Main(args As String())
                    Dim S1 As S
                    S1.x = ""
                    Dim S2 = S1
                End Sub
            End Module
        </file>
      </compilation>)
 
            Dim tree = compilation.SyntaxTrees(0)
            Dim model = compilation.GetSemanticModel(tree)
            Dim diagnostics = model.GetDiagnostics()
            CompilationUtils.AssertTheseDiagnostics(diagnostics, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub AllPiecesAssigned_Int()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="AllPiecesAssigned_Int">
          <file name="a.b">
Public Structure S
    Public x As Integer
    Public y As Integer
End Structure
 
Public Class Test
    Public Shared Sub Main()
        Dim s As S
        s.x = 1
        s.y = 2
        Dim t As S = s
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub AllPiecesAssigned_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="AllPiecesAssigned_Obj">
          <file name="a.b">
Public Structure S
    Public x As Object
    Public y As Object
End Structure
 
Public Class Test
    Public Shared Sub Main(args As String())
        Dim s As S
        s.x = args(0)
        s.y = New Object()
        Dim t As S = s
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub AllPiecesAssigned_Prop_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="AllPiecesAssigned_Prop_Obj">
          <file name="a.b">
Public Structure S
    Public Property x As Object
    Public Property y As Object
End Structure
 
Public Class Test
    Public Shared Sub Main()
        Dim s As S
        s.x = 1
        s.y = 2
        Dim t As S = s
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        s.x = 1
        ~
</errors>)
        End Sub
 
        <Fact>
        Public Sub OnePieceMissing_Int()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="OnePieceMissing_Int">
          <file name="a.b">
Public Structure S
    Public x As Integer
    Public y As Integer
End Structure
 
Public Class Test
    Public Shared Sub Main(args As String())
        Dim s As S
        s.x = args.Length
        Dim t As S = s
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub OnePieceMissing_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="OnePieceMissing_Obj">
          <file name="a.b">
Public Structure S
    Public x As Object
    Public y As Object
End Structure
 
Public Class Test
    Public Shared Sub Main(args As String())
        Dim s As S
        s.y = New Object()
        Dim t As S = s
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        Dim t As S = s
                     ~
</errors>)
        End Sub
 
        <Fact>
        Public Sub OnePieceMissing_Prop_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="OnePieceMissing_Prop_Obj">
          <file name="a.b">
Public Structure S
    Public Property x As Object
    Public Property y As Object
End Structure
 
Public Class Test
    Public Shared Sub Main(args As String())
        Dim s As S
        s.y = New Object()
        Dim t As S = s
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        s.y = New Object()
        ~
</errors>)
        End Sub
 
        <Fact>
        Public Sub OnePieceOnOnePath_Int()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="OnePieceOnOnePath_Int">
          <file name="a.b">
Public Structure S
    Public x As Integer
    Public y As Integer
End Structure
 
Public Class Test
    Public Shared Sub Main(s As S)
        Dim s2 As S
        If s.x = 3 Then
            s2 = s
        Else
            s2.x = s.x
        End If
        Dim i As Integer = s2.x
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub OnePieceOnOnePath_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="OnePieceOnOnePath_Obj">
          <file name="a.b">
Public Structure S
    Public x As Object
    Public y As Object
End Structure
 
Public Class Test
    Public Shared Sub Main(s As S)
        Dim s2 As S
        If s.x Is New Object() Then
            s2 = s
        Else
            s2.x = s.x
        End If
        Dim i As Object = s2.x
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub OnePieceOnOnePath_Prop_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="OnePieceOnOnePath_Prop_Obj">
          <file name="a.b">
Public Structure S
    Public Property x As Object
    Public Property y As Object
End Structure
 
Public Class Test
    Public Shared Sub Main(s As S)
        Dim s2 As S
        If s.x Is New Object() Then
            s2 = s
        Else
            s2.x = s.x
        End If
        Dim i As Object = s2.x
    End Sub
End Class
</file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 's2' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
            s2.x = s.x
            ~~
</errors>)
        End Sub
 
        <Fact>
        Public Sub FullInitializationInConstructor_Int()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="FullInitializationInConstructor_Int">
          <file name="a.b">
Public Structure S
    Public x As Integer
    Public y As Integer
    Public Sub New(p As Integer)
        Me.x = p
        Me.y = p
    End Sub
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub FullInitializationInConstructor_Prop_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="FullInitializationInConstructor_Prop_Obj">
          <file name="a.b">
Public Structure S
    Public Property x As Object
    Public Property y As Object
    Public Sub New(p As Object)
        Me.x = p
        Me.y = p
    End Sub
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub PartialInitializationInConstructor_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="PartialInitializationInConstructor_Obj">
          <file name="a.b">
Public Structure S
    Public x As Object
    Public y As Object
    Public Sub New(p As Object)
        Me.x = p
    End Sub
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub PartialInitializationInConstructor_Prop_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="PartialInitializationInConstructor_Prop_Obj">
          <file name="a.b">
Public Structure S
    Public Property x As Object
    Public Property y As Object
    Public Sub New(p As Object)
        Me.x = p
    End Sub
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub DefaultConstructor_Int()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="DefaultConstructor_Int">
          <file name="a.b">
Public Structure S
    Public x As Integer
    Public y As Integer
End Structure
Public Class Test
    Public Shared Sub Main()
        Dim s As S = New S()
        s.x = s.y
        s.y = s.x
    End Sub
End Class
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub DefaultConstructor_Prop_And_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="DefaultConstructor_Prop_And_Obj">
          <file name="a.b">
Public Structure S
    Public x As Object
    Public Property y As Object
End Structure
Public Class Test
    Public Shared Sub Main()
        Dim s As S = New S()
        s.x = s.y
        s.y = s.x
    End Sub
End Class
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub AutoPropInitialization_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="AutoPropInitialization_Obj">
          <file name="a.b">
Public Structure S
    Public Property x As Object
    Public Sub New(y As Object)
    End Sub
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub EmptyStructAlwaysAssigned_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="EmptyStructAlwaysAssigned_Obj">
          <file name="a.b">
Public Structure S
End Structure
Public Structure SS
    Public s1 As S
    Public s2 As S
    Public Function F() As SS
        Dim ret As SS
        Return ret
    End Function
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
        <Fact>
        Public Sub Struct_WithStructProperty_Auto_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="Struct_WithStructProperty_Auto_Obj">
          <file name="a.b">
Public Structure S
    Public Property P As Object
End Structure
Public Structure SS
    Public s As S
    Public Function F() As SS
        Dim ret As SS
        ret.s.P = Nothing
        Return ret
    End Function
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation,
<errors>
BC42109: Variable 's' is used before it has been assigned a value. A null reference exception could result at runtime. Make sure the structure or all the reference members are initialized before use
        ret.s.P = Nothing
        ~~~~~
</errors>)
        End Sub
 
        <Fact>
        Public Sub Struct_WithStructProperty_Obj()
            Dim compilation = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation name="Struct_WithStructProperty_Obj">
          <file name="a.b">
Public Structure S
    Public Property P As Object
        Get
            Return Nothing
        End Get
        Set(value As Object)
        End Set
    End Property
End Structure
Public Structure SS
    Public s As S
    Public Function F() As SS
        Dim ret As SS
        ret.s.P = 0
        Return ret
    End Function
End Structure
        </file>
      </compilation>)
            CompilationUtils.AssertTheseDiagnostics(compilation, <errors></errors>)
        End Sub
 
#End Region
 
        <WorkItem(874526, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/874526")>
        <Fact()>
        Public Sub GenericStructWithPropertyUsingStruct()
            Dim comp = CompilationUtils.CreateCompilationWithMscorlib40(
      <compilation>
          <file name="a.b">
Structure S(Of T)
    Property P As S(Of T())?
End Structure
        </file>
      </compilation>)
            comp.AssertTheseDiagnostics(
<errors>
BC30294: Structure 'S' cannot contain an instance of itself: 
    'S(Of T)' contains 'S(Of T())?' (variable '_P').
    'S(Of T())?' contains 'S(Of T())' (variable 'value').
    Property P As S(Of T())?
             ~
</errors>)
        End Sub
 
    End Class
 
End Namespace
File: FlowAnalysis\StructureAnalysisTests.vb	Web Access
Project: src\src\Compilers\VisualBasic\Test\Semantic\Microsoft.CodeAnalysis.VisualBasic.Semantic.UnitTests.vbproj (Microsoft.CodeAnalysis.VisualBasic.Semantic.UnitTests)