Expose the compiler's helper to find ConditionalAccessExpressions at the...

Expose the compiler's helper to find ConditionalAccessExpressions at the Workspace layer. 1113971 tracks making this a public API in the compiler. (changeset 1411035)

src/EditorFeatures/VisualBasicTest/Completion/CompletionProviders/SymbolCompletionProviderTests.vb

@@ -5319,7 +5319,64 @@ End Module
             VerifyItemExists(text, "ToString")
         End Sub
 
-        <WorkItem(1079694)>
+		<WorkItem(1109319)>
+		<Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+		Public Sub UnwrapNullableForConditionalFromStructure()
+			Dim text =
+<code><![CDATA[
+Module Program
+    Sub Main(args As String())
+        Dim x As A
+        x?.$$b?.c
+    End Sub
+End Module
+
+Structure A
+    Public b As B
+End Structure
+
+Public Class B
+    Public c As C
+End Class
+
+Public Class C
+End Class
+]]></code>.Value
+
+			VerifyItemExists(text, "b")
+			VerifyItemIsAbsent(text, "c")
+		End Sub
+
+		<WorkItem(1109319)>
+		<Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+		Public Sub WithinChainOfConditionalAccess()
+			Dim text =
+<code><![CDATA[
+Module Program
+    Sub Main(args As String())
+        Dim x As A
+        x?.$$b?.c
+    End Sub
+End Module
+
+Class A
+    Public b As B
+End Class
+
+Public Class B
+    Public c As C
+End Class
+
+Public Class C
+End Class
+]]></code>.Value
+
+			VerifyItemExists(text, "b")
+			VerifyItemIsAbsent(text, "c")
+		End Sub
+
+
+		<WorkItem(1079694)>
         <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
         Public Sub DontThrowForNullPropagatingOperatorOnTypeParameter()
             Dim text =

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

@@ -68,15 +68,27 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Extensions
 
         End Function
 
-        <Extension>
-        Public Function GetExpressionOfMemberAccessExpression(memberAccessExpression As MemberAccessExpressionSyntax) As ExpressionSyntax
-            If memberAccessExpression Is Nothing Then
-                Return Nothing
-            End If
+		<Extension>
+		Public Function GetExpressionOfMemberAccessExpression(memberAccessExpression As MemberAccessExpressionSyntax) As ExpressionSyntax
+			If memberAccessExpression Is Nothing Then
+				Return Nothing
+			End If
 
-            If memberAccessExpression.Expression IsNot Nothing Then
-                Return memberAccessExpression.Expression
-            End If
+			If memberAccessExpression.Expression IsNot Nothing Then
+				Return memberAccessExpression.Expression
+			End If
+
+            ' Maybe we're part of a ConditionalAccessExpression
+            Dim conditional = memberAccessExpression.GetCorrespondingConditionalAccessExpression()
+			If conditional IsNot Nothing Then
+				If conditional.Parent.IsKind(SyntaxKind.ExpressionStatement) AndAlso conditional.Parent.Parent.IsKind(SyntaxKind.WithBlock) AndAlso
+					conditional.Expression Is Nothing Then
+
+					Return DirectCast(conditional.Parent.Parent, WithBlockSyntax).WithStatement.Expression
+				End If
+
+				Return conditional.Expression
+			End If
 
             ' we have a member access expression with a null expression, this may be one of the
             ' following forms:
@@ -84,33 +96,26 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Extensions
             ' 1) new With { .a = 1, .b = .a     <-- .a refers to the anonymous type
             ' 2) With obj : .m                  <-- .m refers to the obj type
             ' 3) new T() With { .a = 1, .b = .a <-- 'a refers to the T type
-            ' 4) With obj : ?.m                 <-- .m refers to the obj type
 
             Dim current As SyntaxNode = memberAccessExpression
 
-            While current IsNot Nothing
-                If TypeOf current Is AnonymousObjectCreationExpressionSyntax Then
-                    Return DirectCast(current, ExpressionSyntax)
-                ElseIf TypeOf current Is WithBlockSyntax Then
-                    Dim withBlock = DirectCast(current, WithBlockSyntax)
-                    If memberAccessExpression IsNot withBlock.WithStatement.Expression Then
-                        Return withBlock.WithStatement.Expression
-                    End If
-                ElseIf TypeOf current Is ObjectMemberInitializerSyntax AndAlso
-                       TypeOf current.Parent Is ObjectCreationExpressionSyntax Then
-                    Return DirectCast(current.Parent, ExpressionSyntax)
-                ElseIf current.IsKind(SyntaxKind.ConditionalAccessExpression) Then
-                    Dim conditionalAccess = DirectCast(current, ConditionalAccessExpressionSyntax)
-
-                    If conditionalAccess.Expression IsNot Nothing Then
-                        Return conditionalAccess.Expression
-                    End If
-                End If
-
-                current = current.Parent
-            End While
-
-            Return Nothing
-        End Function
-    End Module
+			While current IsNot Nothing
+				If TypeOf current Is AnonymousObjectCreationExpressionSyntax Then
+					Return DirectCast(current, ExpressionSyntax)
+				ElseIf TypeOf current Is WithBlockSyntax Then
+					Dim withBlock = DirectCast(current, WithBlockSyntax)
+					If memberAccessExpression IsNot withBlock.WithStatement.Expression Then
+						Return withBlock.WithStatement.Expression
+					End If
+				ElseIf TypeOf current Is ObjectMemberInitializerSyntax AndAlso
+					   TypeOf current.Parent Is ObjectCreationExpressionSyntax Then
+					Return DirectCast(current.Parent, ExpressionSyntax)
+				End If
+
+				current = current.Parent
+			End While
+
+			Return Nothing
+		End Function
+	End Module
 End Namespace

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

@@ -1085,23 +1085,77 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Extensions
             Return SpecializedCollections.EmptyEnumerable(Of SyntaxNode)()
         End Function
 
-        <Extension()>
-        Public Iterator Function GetAliasImportsClauses(root As CompilationUnitSyntax) As IEnumerable(Of SimpleImportsClauseSyntax)
-            For i = 0 To root.Imports.Count - 1
-                Dim statement = root.Imports(i)
-
-                For j = 0 To statement.ImportsClauses.Count - 1
-                    Dim importsClause = statement.ImportsClauses(j)
-
-                    If importsClause.Kind = SyntaxKind.SimpleImportsClause Then
-                        Dim simpleImportsClause = DirectCast(importsClause, SimpleImportsClauseSyntax)
-
-                        If simpleImportsClause.Alias IsNot Nothing Then
-                            Yield simpleImportsClause
-                        End If
-                    End If
-                Next
-            Next
-        End Function
-    End Module
+		<Extension()>
+		Public Iterator Function GetAliasImportsClauses(root As CompilationUnitSyntax) As IEnumerable(Of SimpleImportsClauseSyntax)
+			For i = 0 To root.Imports.Count - 1
+				Dim statement = root.Imports(i)
+
+				For j = 0 To statement.ImportsClauses.Count - 1
+					Dim importsClause = statement.ImportsClauses(j)
+
+					If importsClause.Kind = SyntaxKind.SimpleImportsClause Then
+						Dim simpleImportsClause = DirectCast(importsClause, SimpleImportsClauseSyntax)
+
+						If simpleImportsClause.Alias IsNot Nothing Then
+							Yield simpleImportsClause
+						End If
+					End If
+				Next
+			Next
+		End Function
+
+		''' <summary>
+		''' Given an expression within a tree of <see cref="ConditionalAccessExpressionSyntax"/>s, 
+		''' finds the <see cref="ConditionalAccessExpressionSyntax"/> that it is part of.
+		''' </summary>
+		''' <param name="node"></param>
+		''' <returns></returns>
+		<Extension>
+		Friend Function GetCorrespondingConditionalAccessExpression(node As ExpressionSyntax) As ConditionalAccessExpressionSyntax
+			Dim access As SyntaxNode = node
+			Dim parent As SyntaxNode = access.Parent
+
+			While parent IsNot Nothing
+				Select Case parent.Kind
+					Case SyntaxKind.DictionaryAccessExpression,
+						 SyntaxKind.SimpleMemberAccessExpression
+
+						If DirectCast(parent, MemberAccessExpressionSyntax).Expression IsNot access Then
+							Return Nothing
+						End If
+
+					Case SyntaxKind.XmlElementAccessExpression,
+						 SyntaxKind.XmlDescendantAccessExpression,
+						 SyntaxKind.XmlAttributeAccessExpression
+
+						If DirectCast(parent, XmlMemberAccessExpressionSyntax).Base IsNot access Then
+							Return Nothing
+						End If
+
+					Case SyntaxKind.InvocationExpression
+
+						If DirectCast(parent, InvocationExpressionSyntax).Expression IsNot access Then
+							Return Nothing
+						End If
+
+					Case SyntaxKind.ConditionalAccessExpression
+
+						Dim conditional = DirectCast(parent, ConditionalAccessExpressionSyntax)
+						If conditional.WhenNotNull Is access Then
+							Return conditional
+						ElseIf conditional.Expression IsNot access Then
+							Return Nothing
+						End If
+
+					Case Else
+						Return Nothing
+				End Select
+
+				access = parent
+				parent = access.Parent
+			End While
+
+			Return Nothing
+		End Function
+	End Module
 End Namespace