Extra reportsUnnecessary suggestions for syntactically invalid file

[mjbvz]

From microsoft/vscode#52346

TypeScript Version: 3.0.0-dev.20180706

Search Terms:

• reportsUnnecessary
• diagnostics
• suggestions

Code
For the invalid code (with extra d after the 1):

export const _ = 1;

const a = 1 d;

Bug
See a suggestion diagnostic:

  {
            "start": {
                "line": 3,
                "offset": 1
            },
            "end": {
                "line": 3,
                "offset": 15
            },
            "text": "All variables are unused.",
            "code": 6199,
            "category": "suggestion",
            "reportsUnnecessary": true
        }

This causes the entire line to become faded out. I do not believe we should report these errors when there are syntax errors

[mjbvz]

Another minimal example that has an extra unused diagnostic:

({
    a: 1
}
b: 1
})

b is reported as an unused label

[mhegazy]

Not sure what is the best solution here. @Andy-MS thoughts?

It would probably be fine to never add suggestions when any parse errors exist.

[mjbvz]

Yes that sounds reasonable overall. Will have to see if it causes flickering in the editor though while users are writing