Tweak error counting.

We have several methods indicating the presence of errors, lint errors,
and delayed bugs. I find it frustrating that it's very unclear which one
you should use in any particular spot. This commit attempts to instill a
basic principle of "use the least general one possible", because that
reflects reality in practice -- `has_errors` is the least general one
and has by far the most uses (esp. via `abort_if_errors`).

Specifics:
- Add some comments giving some usage guidelines.
- Prefer `has_errors` to comparing `err_count` to zero.
- Remove `has_errors_or_span_delayed_bugs` because it's a weird one: in
  the cases where we need to count delayed bugs, we should really be
  counting lint errors as well.
- Rename `is_compilation_going_to_fail` as
  `has_errors_or_lint_errors_or_span_delayed_bugs`, for consistency with
  `has_errors` and `has_errors_or_lint_errors`.
- Change a few other `has_errors_or_lint_errors` calls to `has_errors`,
  as per the "least general" principle.

This didn't turn out to be as neat as I hoped when I started, but I
think it's still an improvement.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/librustdoc/scrape_examples.rs b/src/librustdoc/scrape_examples.rs
index 74bec5a2e11..b7d9c16f348 100644
--- a/src/librustdoc/scrape_examples.rs
+++ b/src/librustdoc/scrape_examples.rs
@@ -311,7 +311,7 @@ pub(crate) fn run(
 
         // The visitor might have found a type error, which we need to
         // promote to a fatal error
-        if tcx.dcx().has_errors_or_lint_errors().is_some() {
+        if tcx.dcx().has_errors().is_some() {
             return Err(String::from("Compilation failed, aborting rustdoc"));
         }