CS0136Test.cs

using System;
using System.Globalization;
using System.Threading;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;

class Program
{
    static void Main(string[] args)
    {
        Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
        Console.WriteLine("Roslyn v" + typeof(CSharpCompilation).Assembly.GetName().Version);

        var testSource = @"using System;
class Program
{
    static void Main(string[] args)
    {
        var (foo, bar) = F(() =>
        {
            return F(() =>
            {
                var foo = 0;
                var bar = 1;
                return (foo, bar);
            });
        });
    }
    static T F<T>(Func<T> x) => x();
}";

        var compilation = CSharpCompilation.Create(
            "CS0136Test",
            new SyntaxTree[] { CSharpSyntaxTree.ParseText(testSource) },
            new MetadataReference[] { MetadataReference.CreateFromFile(typeof(string).Assembly.Location) }
        );

        Console.WriteLine("Library");
        foreach (var diag in compilation.GetDiagnostics())
        {
            Console.WriteLine(diag);
        }

        var testScript = @"using System;
T F<T>(Func<T> x) => x();
var (foo, bar) = F(() =>
{
    return F(() => {
        var foo = 0;
        var bar = 1;
        return (foo, bar);
    });
});";

        var scriptCompilation = CSharpCompilation.CreateScriptCompilation(
            "CS0136Test",
            CSharpSyntaxTree.ParseText(testScript, new CSharpParseOptions(kind: SourceCodeKind.Script)),
            new MetadataReference[] { MetadataReference.CreateFromFile(typeof(string).Assembly.Location) }
        );

        Console.WriteLine();
        Console.WriteLine("Script");
        foreach (var diag in scriptCompilation.GetDiagnostics())
        {
            Console.WriteLine(diag);
        }
    }
}

/*
Roslyn v2.9.0.0
Library
(10,21): error CS0136: A local or parameter named 'foo' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter
(11,21): error CS0136: A local or parameter named 'bar' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter

Script 
*/