Added: LDM Notes for July 26th, 2021

[333fred]

https://github.com/dotnet/csharplang/blob/main/meetings/2021/LDM-2021-07-26.md

Agenda

1. Lambda conversion to System.Delegate
2. Direct invocation of lambdas
3. Speakable names for top-level statements

[ufcpp]

One concern I have is nullability attributes on lambdas:

// Local functions
using System.Diagnostics.CodeAnalysis;

[return: NotNullIfNotNull("s")] string? m(string? s) => s;
string notNull = m(""); // no warning
string maybeNull = m(null); // warning

// Explicitly typed delegates
using System.Diagnostics.CodeAnalysis;

// Type parameters can not have attributes such as NotNullIfNotNull
Func<string?, string?> f = [return: NotNullIfNotNull("s")] string? (string? s) => s;
string notNull = f(""); // warning (not desirable?)

// Direct invocation of lambdas
using System.Diagnostics.CodeAnalysis;
string notNull = ([return: NotNullIfNotNull("s")] string? (string? s) => s)(""); // shouldn't warn?

[RikkiGibson]

Interesting point. It feels like ideally the following would not warn either

// Direct invocation of lambdas
using System.Diagnostics.CodeAnalysis;
var func = [return: NotNullIfNotNull("s")] string? (string? s) => s;
string notNull = func(""); // shouldn't warn?

However, I think it's most likely that the implementation does warn here, and wouldn't particularly suggest that we invest in changing that.