Ignore constant expressions in CapturedVariableRewriter

The VB EE runs ```CapturedVariableRewriter```, so it ends up looking
inside constants that will be rewritten into literal expressions in
```LocalRewriter```.  This can result in spurious errors - e.g. when
accessing an instance member in a ```nameof``` expression in a
```shared``` context.

C# is unaffected since it runs ```CapturedVariableRewriter``` after
```LocalRewriter```.

Fixes #3939

src/ExpressionEvaluator/VisualBasic/Source/ExpressionCompiler/Rewriters/CapturedVariableRewriter.vb

@@ -31,6 +31,15 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.ExpressionEvaluator
             _diagnostics = diagnostics
         End Sub
 
+        Public Overrides Function Visit(node As BoundNode) As BoundNode
+            ' Ignore nodes that will be rewritten to literals in the LocalRewriter.
+            If TryCast(node, BoundExpression)?.ConstantValueOpt IsNot Nothing Then
+                Return node
+            End If
+
+            Return MyBase.Visit(node)
+        End Function
+
         Public Overrides Function VisitBlock(node As BoundBlock) As BoundNode
             Dim rewrittenLocals = node.Locals.WhereAsArray(AddressOf IncludeLocal)
             Dim rewrittenStatements = VisitList(node.Statements)

src/ExpressionEvaluator/VisualBasic/Test/ExpressionCompiler/ExpressionCompilerTests.vb

@@ -4583,6 +4583,61 @@ End Class"
             Assert.Same(previous, context)
         End Sub
 
+        <WorkItem(3939, "https://github.com/dotnet/roslyn/issues/3939")>
+        <Fact>
+        Public Sub NameofInstanceInSharedContext()
+            Const source = "
+Class C
+    Private X As Integer
+    Shared Function M() As String
+        Return Nameof(X)
+    End Function
+End Class
+"
+            Dim resultProperties As ResultProperties = Nothing
+            Dim errorMessage As String = Nothing
+            Dim testData = Evaluate(
+                source,
+                OutputKind.DynamicallyLinkedLibrary,
+                methodName:="C.M",
+                expr:="Nameof(X)",
+                resultProperties:=resultProperties,
+                errorMessage:=errorMessage)
+            Assert.Null(errorMessage)
+            testData.GetMethodData("<>x.<>m0").VerifyIL("
+{
+  // Code size        6 (0x6)
+  .maxstack  1
+  .locals init (String V_0) //M
+  IL_0000:  ldstr      ""X""
+  IL_0005:  ret
+}
+")
+        End Sub
+
+        <WorkItem(3939, "https://github.com/dotnet/roslyn/issues/3939")>
+        <Fact>
+        Public Sub NameofInstanceInSharedContext_ExplicitMe()
+            Const source = "
+Class C
+    Private X As Integer
+    Shared Function M() As String
+        Return Nameof(X)
+    End Function
+End Class
+"
+            Dim resultProperties As ResultProperties = Nothing
+            Dim errorMessage As String = Nothing
+            Dim testData = Evaluate(
+                source,
+                OutputKind.DynamicallyLinkedLibrary,
+                methodName:="C.M",
+                expr:="Nameof(Me.X)",
+                resultProperties:=resultProperties,
+                errorMessage:=errorMessage)
+            Assert.Equal("(1) : error BC30043: 'Me' is valid only within an instance method.", errorMessage)
+        End Sub
+
     End Class
 
 End Namespace
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