return_linter() for implicit returns has a false positive on nested early returns

[MichaelChirico]

          Corrected this test, and added the incorrect test as a new regression test.

That said, the new fix is more expedient than perfect -- it'll throw an incorrect lint here:

foo <- function() {
  if (TRUE) {
    if (TRUE) {
      return(1)
    }
    2
  } else {
    3
  }

(the return() is a valid early return within that branch).

But as this issue is not relevant to the implicit else returns feature, I'm pushing to follow-up.

Originally posted by @MichaelChirico in #2321 (comment)

[MichaelChirico]

Test case for regression:

test_that("explicit returns in control flow are linted", {
  lint_msg <- rex::rex("Use implicit return behavior")

  expect_lint(
    trim_some("
      foo <- function(bar) {
        if (TRUE) {
          return(bar)
        } else {
          return(NULL)
        }
      }
    "),
    list(lint_msg, lint_msg),
    return_linter()
  )
})

[MichaelChirico]

Also ensure that e.g. R/any_duplicated_linter.R does not lint.