Roslyn: Keyword recommender doesn't know about struct's readonly members

[huoyaoyuan]

Version Used:
VS 16.3.4

struct S
{
    readonly $$
}

No void keyword here. A readonly void method could still modify global state using the value of instance state, so still meaningful.

---

struct S
{
    public $$ int X() => 1;
}

readonly presents here.

---

struct S
{
    public int X
    {
        $$ get => 1;
    }
}

No readonly here.

---

struct S
{
    public int X
    {
        $$
    }
}

No readonly here.

---

struct S
{
    public int X
    {
        readonly $$
    }
}

Recommending types instead of accessor keywords.

[sharwell]

@dotnet/roslyn-compiler can you verify all of these locations so we can get them implemented?

[huoyaoyuan]

I have done some investigation:

https://github.com/dotnet/roslyn/blob/97b75fcb5807881b0e768357b82c1a3476a3ec2c/src/Workspaces/CSharp/Portable/Utilities/SyntaxKindSet.cs#L24-L42
Should include ref keyword.

https://github.com/dotnet/roslyn/blob/97b75fcb5807881b0e768357b82c1a3476a3ec2c/src/Workspaces/CSharp/Portable/Extensions/ContextQuery/SyntaxTokenExtensions.cs#L546-L551
Should think readonly a modifier.

https://github.com/dotnet/roslyn/blob/97b75fcb5807881b0e768357b82c1a3476a3ec2c/src/Workspaces/CSharp/Portable/Extensions/ContextQuery/SyntaxTreeExtensions.cs#L288-L289
Should be MemberDeclarationSyntax. BaseTypeDeclarationSyntax and ImcompleteMemberSyntax both derives from it.

https://github.com/dotnet/roslyn/blob/97b75fcb5807881b0e768357b82c1a3476a3ec2c/src/Workspaces/CSharp/Portable/Extensions/ContextQuery/SyntaxTreeExtensions.cs#L708-L709
Don't assume member declaration when seeing readonly.
The implementation in #25570 is rude. https://github.com/dotnet/roslyn/pull/25570/files#r175509814

After doing those, most tests are passing except these two:
https://github.com/dotnet/roslyn/blob/97b75fcb5807881b0e768357b82c1a3476a3ec2c/src/EditorFeatures/CSharpTest/Completion/CompletionProviders/SymbolCompletionProviderTests.cs#L2215-L2247

[jaredpar]

@RikkiGibson

[RikkiGibson]

can you verify all of these locations so we can get them implemented?

All of the locations mentioned by @huoyaoyuan look like valid places to recommend the keyword to me.

[huoyaoyuan]

And there may be some clearification for readonly ref readonly. Quite confusing for ones haven't read changelog.