Circular imports are not possible and will lead to a compilation error.

-- Testcase --
import a_val from "./files/a.uc";
-- End --

-- File a.uc --
import b_val from "./b.uc";
export default "a";
-- End --

-- File b.uc --
import a_val from "./a.uc";
export default "b";
-- End --

-- Args --
-R
-- End --

-- Expect stderr --
Syntax error: Unable to compile module './files/a.uc':

  | Syntax error: Unable to compile module './files/b.uc':
  |
  |   | Syntax error: Circular dependency
  |   | In ./files/b.uc, line 1, byte 19:
  |   |
  |   |  `import a_val from "./a.uc";`
  |   |   Near here --------^
  |
  | In ./files/a.uc, line 1, byte 27:
  |
  |  `import b_val from "./b.uc";`
  |   Near here ----------------^

In [stdin], line 1, byte 33:

 `import a_val from "./files/a.uc";`
  Near here ----------------------^


-- End --