Fix latest tslint errors

[saschanaz]

Except this type of errors:

export function getNavigationTree(sourceFile: SourceFile): NavigationTree {
    curSourceFile = sourceFile;
    const result = convertToTree(rootNavigationBarNode(sourceFile));
    curSourceFile = undefined;
    return result;
}
let curSourceFile: SourceFile;
// Identifier 'curSourceFile' is never reassigned; use 'const' instead of 'let'.

let response: protocol.Response;
try {
    ({ response } = this.executeCommand(msg));
}
//  Identifier 'response' is never reassigned; use 'const' instead of 'let'.

I think they are tslint bugs rather than actual code problem. (palantir/tslint#1898)

BTW I feel fairly painful to create a new constant for every for-loop, I hope there is a better way to keep high performance...

[saschanaz]

A benchmark shows for-of loop is much slower on Chrome (and thus node.js), does this mean we shouldn't use for-of?

[ghost]

for-of gets emitted as a for loop, since we use an ES5 target. (So maybe some of those manually-written for loops could be upgraded.)
Also, this would be a good time to delete our own preferConstRule.ts since tslint has that now.

[saschanaz]

Already done the upgrade for obvious cases but many of them are using indices so I couldn't do it for them.

[mhegazy]

I would inline the collection.length check instead of adding a new variable for it. There is not much perf difference on modern engines anyways.

[mhegazy]

switch to for..of?

[saschanaz]

Inner lines of code use i for some purpose. It seems I can still switch to for-of in this case but should I do it?

[mhegazy]

for (let i = isJSConstructSignature ? 1 : 0; i < declaration.parameters.length; i++) {

[mhegazy]

@saschanaz i have merged a change to move tslint back to 4.0.0-dev.3 (#13028). can you update it with your PR to next again.

[saschanaz]

It still won't pass because of some bugs, which should be fixed on tslint side.

[mhegazy]

It still won't pass because of some bugs, which should be fixed on tslint side.

do you have a list of the issues?

[ghost]

@mhegazy See first post and palantir/tslint#1898. I actually fixed one of them yesterday. The other one is also a legitimate issue, but could be fixed on our end by moving the declaration ( let curSourceFile: SourceFile;) to before the function.

[saschanaz]

@Andy-MS I'm still seeing destructuring issue on Travis, should I do something to get the merged fix?

[ghost]

tslint hasn't published a new version yet, so there's not much to do but wait.

[vladima]

I'd prefer not to change our code to workaround bugs in the toolchain hence palantir/tslint#1908

[mhegazy]

@nchen63 any news about palantir/tslint#1908?

[nchen63]

it's merged and included in a new release, v4.2.0

[saschanaz]

It seems tslint@next is still giving tslint@4.1.0-dev.0.

[nchen63]

should be fixed now