code: def line_is_installable(self):
          # type: () -> bool
          
          line = self.line
          if is_file_url(line):
              link = create_link(line)
              line = link.url_without_fragment
              line, _ = split_ref_from_uri(line)
          if (
              is_vcs(line)
              or (
                  is_valid_url(line)
                  and (not is_file_url(line) or is_installable_file(line))
              )
              or is_installable_file(line)
          ):
              return True
          return False
docs: This is a safeguard against decoy requirements when a user installs a package
          whose name coincides with the name of a folder in the cwd, e.g. install *alembic*
          when there is a folder called *alembic* in the working directory.
  
          In this case we first need to check that the given requirement is a valid
          URL, VCS requirement, or installable filesystem path before deciding to treat it
          as a file requirement over a named requirement.