handle forward referenced in prefer-const rule

[vladima]

fixes error related to usage of forward references in prefer-const rule

PR checklist

• Addresses an existing issue: tslint@next does not recognize some reassignation #1898
• New feature, bugfix, or enhancement - bugfix
  • Includes tests
• Documentation update - N/A

What changes did you make?

After this change list of variable declarations in block scope is collected immediately after entering the scope. This prevents cases when variable is syntactically located after its usage

[palantirtech]

Thanks for your interest in palantir/tslint, @vladima! Before we can accept your pull request, you need to sign our contributor license agreement - just visit https://cla.palantir.com/ and follow the instructions. Once you sign, I'll automatically update this pull request.

[nchen63]

@vladima can you turn on circle ci?

[nchen63]

Doesn't seem to catch:

module MyModule {
    let moduleMember = 4;
}

[vladima]

@nchen63 yes, if you can tell me how to do it

[nchen63]

go to https://circleci.com/add-projects and add your fork

[vladima]

done

[nchen63]

another case that isn't caught - inside a switch statement

[nchen63]

that's weird, CircleCI isn't running still. Can you fix the linting errors when you run npm run verify?

[nchen63]

Looks good. Thanks!