CS1591 incorrectly reported for records defined using the short syntax

[WilStead]

Version Used: Version 16.8.0 Preview 2.0

Steps to Reproduce:

1. Enable XML documentation

<PropertyGroup>
  <GenerateDocumentationFile>true</GenerateDocumentationFile>
</PropertyGroup>

2. (Taken directly from the ASP.NET Core .NET 5 Preview 8 blog post)

public record Person([Required] string Name, [Range(0, 150)] int Age);

Expected Behavior: No warnings

Actual Behavior:
CS1591 reported for both parameters (properties?).

This might actually be a valid warning, except that there is no mechanism to add such documentation. For example:

public record Person
(
    /// <summary>
    /// The person's name.
    /// </summary>
    [Required] string Name
);

The above produces CS1587 instead: XML comment is not placed on a valid language element.

I am also unaware of any tag which might be added to the record itself to document the parameters. For example:

/// <summary>
/// A person.
/// </summary>
/// <property cref="Name">
/// The person's name.
/// </property>
public record Person([Required] string Name);

This hypothetical syntax is invalid (produces CS1574 and fails to remove CS1591), but I could imagine something like it being used to document the auto-generated properties in a way that satisfies CS1591.

[RikkiGibson]

This could require a language design decision: is a doc comment directly on the parameter valid, or is a new kind of doc comment on the record declaration required. FYI @jcouv @333fred

When I tried adopting records in a personal project it felt natural to me to put the doc comment directly on the parameter, since I was basically refactoring auto-property declarations into record parameters.

[jcouv]

xml doc work for records is tracked in #44571
That includes a summary of the plan (we'll allow <param> on the record type to carry over to the primary constructor parameters).

[333fred]

Duplicate of #44571. I'll add a note to that issue to make sure we consider this warning, but we should have 1 issue tracking this.