Compiler crash generating XML docs for extension

[BillWagner]

Version Used: Compiler version: '5.0.0-1.25258.110 (c22dcd0c)'. Language version: preview. (as reported by #error version)

Steps to Reproduce:

Use this source:

namespace ClassLibrary6;

/// <summary>Summary for E</summary>
public static class E
{
    /// <summary>Summary for extension block</summary>
    /// <typeparam name="T">Description for T</typeparam>
    /// <param name="t">Description for t</param>
    extension<T>(T t)
    {
        /// <summary>Summary for M</summary>
        /// <typeparam name="U">Description for U</typeparam>
        /// <param name="u">Description for u</param>
        public void M<U>(U u) => throw null!;

        /// <summary>Summary for P</summary>
        public int P => 0;
    }
}

Set the flag to generate XML docs: <GenerateDocumentationFile>True</GenerateDocumentationFile>

Diagnostic Id:

CSC : error CS1569: Error writing to XML documentation file: Object reference not set to an instance of an object.

From some of my related experiments:

• This class compiles when GenerateDocumentationFile is false or not set.
• XML docs can be generated when the receiver isn't a type parameter. (It can include a type parameter, such as IEnumerable<T>, but it can't be a type parameter like T.

[BillWagner]

@jcouv PTAL

[BillWagner]

/cc @huangmin-ms

[jcouv]

The compiler version you used is too old by just a week to get the xml docs support.

This compiler uses bits from Apr 23rd: c22dcd0c -> https://github.com/dotnet/dotnet/blob/c22dcd0c7a78d095a94d20e59ec0271b9924c82c/src/source-manifest.json -> 1a8d44a

But XML docs support was added on Apr 30th: #78365

[jcouv]

I just tried this in a newer version of VS next and was able to generate an xml doc (compiler no longer crashes).
But the xml generated had an issue, the name of the extension blocks (such as <>E__0) needs to be escaped.
I have a fix pending for this (#78735).
The workaround is to replace <> with <> in the xml file in the meantime.

[huangmin-ms]

The compiler version you used is too old by just a week to get the xml docs support.

This compiler uses bits from Apr 23rd: c22dcd0c -> https://github.com/dotnet/dotnet/blob/c22dcd0c7a78d095a94d20e59ec0271b9924c82c/src/source-manifest.json -> 1a8d44a

But XML docs support was added on Apr 30th: #78365

@jcouv I already using VS preview and the latest .NET10 SDK from https://dotnet.microsoft.com/en-us/download/dotnet

But the compiler version is still: Compiler version: '5.0.0-1.25258.110 (c22dcd0c)'. Language version: preview.
How to upgrade to the version you mentioned above?