Merge latest bits from main branch into extensions branch

[jcouv]

The last two three commits resolve conflicts.

[jjonescz]

Looks like CI run failed: https://dev.azure.com/dnceng-public/public/_build/results?buildId=614874&view=results

I think you might need to merge main again to get #72683 in

[jcouv]

Thanks for the pointer! I'm going to do a new merge from scratch and will force-push, so that the commits for resolving conflicts remain at the end.

[jjonescz]

Previously isMethodGroupConversion was false and now we are passing option IsMethodGroupConversion?

[jcouv]

Mistake on my part

[jjonescz]

Why has this changed?

[jcouv]

That's the way this test without the extension now behaves in main branch where some changes relative to dynamic were made.
Given that this scenario doesn't actually involve the extension member, I didn't investigate further.

[AlekseyTs]

That's the way this test without the extension now behaves in main branch where some changes relative to dynamic were made. Given that this scenario doesn't actually involve the extension member, I didn't investigate further.

The behavior looks consistent with early bound case (no dynamic involved):

        [Fact]
        public void Test()
        {
            var source = """
C.M(1);
class C
{
    public static void M(int d)
    {
        System.Console.Write((new C())[d]);
    }
    public int this[int i] => 42;
}
""";
            var comp = CreateCompilation(source, targetFramework: TargetFramework.Net70);
            CompileAndVerify(comp, expectedOutput: ("42"), verify: Verification.FailsPEVerify).VerifyDiagnostics();
            var tree = comp.SyntaxTrees.First();
            var model = comp.GetSemanticModel(tree);
            var memberAccess = GetSyntax<ElementAccessExpressionSyntax>(tree, "(new C())[d]");
            Assert.Equal("System.Int32 C.this[System.Int32 i] { get; }", model.GetSymbolInfo(memberAccess).Symbol.ToTestDisplayString());
            Assert.Equal([], model.GetMemberGroup(memberAccess).ToTestDisplayStrings());
        }

[AlekseyTs]

Done with review pass (commit 1083)

[AlekseyTs]

LGTM (commit 1084)