error TS6504: File 'tests/cases/compiler/a.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
  The file is in the program because:
    Root file specified for compilation


!!! error TS6504: File 'tests/cases/compiler/a.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504:   The file is in the program because:
!!! error TS6504:     Root file specified for compilation
==== tests/cases/compiler/a.js (0 errors) ====
    declare var v;