[Fact]
    public void Cref_01()
    {
        var src = """
/// <see cref="E.extension(int).this[string]"/>
/// <see cref="E.extension(int).get_Item(string)"/>
public static class E
{
    extension(int i)
    {
        /// <summary></summary>
        public int this[string s]
        {
            get => throw null;
            set => throw null;
        }
    }
}
""";

        // Tracked by https://github.com/dotnet/roslyn/issues/78830 : diagnostic quality, it would be better if the location for the "feature not available" errors pointed to the extension keyword only
        CreateCompilation(src, parseOptions: TestOptions.Regular13.WithDocumentationMode(DocumentationMode.Diagnose)).VerifyEmitDiagnostics(
            // (1,16): warning CS1574: XML comment has cref attribute 'extension(int).this[string]' that could not be resolved
            // /// <see cref="E.extension(int).this[string]"/>
            Diagnostic(ErrorCode.WRN_BadXMLRef, "E.extension(int).this[string]").WithArguments("extension(int).this[string]").WithLocation(1, 16),
            // (1,18): error CS8652: The feature 'extension indexers' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
            // /// <see cref="E.extension(int).this[string]"/>
            Diagnostic(ErrorCode.ERR_FeatureInPreview, "extension(int).this[string]").WithArguments("extension indexers").WithLocation(1, 18),
            // (2,16): warning CS1574: XML comment has cref attribute 'extension(int).get_Item(string)' that could not be resolved
            // /// <see cref="E.extension(int).get_Item(string)"/>
            Diagnostic(ErrorCode.WRN_BadXMLRef, "E.extension(int).get_Item(string)").WithArguments("extension(int).get_Item(string)").WithLocation(2, 16),
            // (2,18): error CS9260: Feature 'extensions' is not available in C# 13.0. Please use language version 14.0 or greater.
            // /// <see cref="E.extension(int).get_Item(string)"/>
            Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion13, "extension(int).get_Item(string)").WithArguments("extensions", "14.0").WithLocation(2, 18),
            // (5,5): error CS9260: Feature 'extensions' is not available in C# 13.0. Please use language version 14.0 or greater.
            //     extension(int i)
            Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion13, @"extension(int i)
    {
").WithArguments("extensions", "14.0").WithLocation(5, 5),
            // (5,5): error CS0710: Static classes cannot have instance constructors
            //     extension(int i)
            Diagnostic(ErrorCode.ERR_ConstructorInStaticClass, "extension").WithLocation(5, 5),
            // (6,6): error CS1513: } expected
            //     {
            Diagnostic(ErrorCode.ERR_RbraceExpected, "").WithLocation(6, 6),
            // (8,20): error CS0720: 'E.this[string]': cannot declare indexers in a static class
            //         public int this[string s]
            Diagnostic(ErrorCode.ERR_IndexerInStaticClass, "this").WithArguments("E.this[string]").WithLocation(8, 20),
            // (14,1): error CS1022: Type or namespace definition, or end-of-file expected
            // }
            Diagnostic(ErrorCode.ERR_EOFExpected, "}").WithLocation(14, 1));
    }