Unused declaration behavior differs from tsserver

[jakebailey]

Given this code:

function unused() {}

In tsserver without noUnusedLocals, this is grayed out:

With noUnusedLocals, it's grayed out and also gets a warning squiggle:

But, with tsgo's LSP implementation, these differ.

Without noUnusedLocals, there are no diagnostics at all, no graying:

[Trace - 10:37:58 PM] Received response 'textDocument/diagnostic - (14)' in 4ms.
Result: {
    "kind": "full",
    "items": []
}

With noUnusedLocals, it gets an error-level squiggle:

[Trace - 10:37:16 PM] Received response 'textDocument/diagnostic - (13)' in 8ms.
Result: {
    "kind": "full",
    "items": [
        {
            "range": {
                "start": {
                    "line": 0,
                    "character": 9
                },
                "end": {
                    "line": 0,
                    "character": 15
                }
            },
            "severity": 1,
            "code": 6133,
            "source": "ts",
            "message": "'unused' is declared but its value is never read."
        }
    ]
}

We are clearly missing diagnostics and the correct info on diagnostics when we have them.

[jakebailey]

Debugging, I'm not sure suggestion diagnostics are being collected at all! The program/checker have nothing for this code.

[ahejlsberg]

I'll take a look.

[jakebailey]

I have most of a PR locally, but apparently forgot to send it