error TS6504: File 'DifferentNamesSpecified/b.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
  The file is in the program because:
    Part of 'files' list in tsconfig.json


!!! error TS6504: File 'DifferentNamesSpecified/b.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504:   The file is in the program because:
!!! error TS6504:     Part of 'files' list in tsconfig.json
!!! related TS1410 DifferentNamesSpecified/tsconfig.json:3:22: File is matched by 'files' list specified here.
==== DifferentNamesSpecified/tsconfig.json (0 errors) ====
    {
      "compilerOptions": { "out": "test.js" },
      "files": [ "a.ts", "b.js" ]
    }
==== DifferentNamesSpecified/a.ts (0 errors) ====
    var test = 10;