Imported variables that used in string switch are not imported correctly in output

[seanchas116]

I experienced the following problem:

Problem

Variables that are imported with import statement and used in switch statement with string parameter
are not imported correctly in emitted JavaScript (no import statement emitted for those variables).

Using other types than string in switch does not cause the problem oddly.

Version

Version 1.8.0-dev.20151112

Code

mod.ts

export const foo = 1;
export const bar = "2";

test.ts

import {foo, bar} from "./mod";

switch ("foo") {
  case "foo": {
    foo;
  }
  case "bar": {
    bar;
  }
}

Command

tsc test.ts --target es6

Output

tsc does not generate import statement for foo and bar.

test.js

switch ("foo") {
    case "foo":
        foo;
    case "bar":
        bar;
}

[seanchas116]

This problem seems to be introduced since 1.8.0-dev.20151110.

[seanchas116]

I noticed whole type checking doesn't work inside switch (any wrong code inside switch compiles without errors)...

[seanchas116]

Oh this is fixed in #5639