`fixed_regex_linter()` fails with "unrecognized escape" error

[IndrajeetPatil]

A minimal version of code I found in the wild that seems to cause problems for fixed_regex_linter():

strsplit("a/b", "\\/")
#> [[1]]
#> [1] "a" "b"

library(lintr)

lint(
  text = 'strsplit("a/b", "\\/")',
  linters = fixed_regex_linter()
)
#> <text>:1:18: error: [error] '\/' is an unrecognized escape in character string starting ""\/"
#> strsplit("a/b", "\/")
#>                  ^

^{Created on 2022-12-13 with reprex v2.0.2}

[MichaelChirico]

I guess it's the same fix as #1545