Don't report disambiguator error if link would have been ignored

This prevents us from warning on links such as `<hello@example.com>`.
Note that we still warn on links such as `<hello@localhost>` because
they have no dots in them. However, the links will still work, even
though a warning is reported.

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -978,14 +978,18 @@ impl LinkCollector<'_, '_> {
             Ok(Some((d, path))) => (path.trim(), Some(d)),
             Ok(None) => (link.trim(), None),
             Err((err_msg, relative_range)) => {
-                let disambiguator_range = (no_backticks_range.start + relative_range.start)
-                    ..(no_backticks_range.start + relative_range.end);
-                disambiguator_error(self.cx, &item, dox, disambiguator_range, &err_msg);
+                if !should_ignore_link_with_disambiguators(link) {
+                    // Only report error if we would not have ignored this link.
+                    // See issue #83859.
+                    let disambiguator_range = (no_backticks_range.start + relative_range.start)
+                        ..(no_backticks_range.start + relative_range.end);
+                    disambiguator_error(self.cx, &item, dox, disambiguator_range, &err_msg);
+                }
                 return None;
             }
         };
 
-        if path_str.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;".contains(ch))) {
+        if should_ignore_link(path_str) {
             return None;
         }
 
@@ -1515,6 +1519,22 @@ fn range_between_backticks(ori_link: &MarkdownLink) -> Range<usize> {
         ..(ori_link.range.start + before_second_backtick_group)
 }
 
+/// Returns true if we should ignore `link` due to it being unlikely
+/// that it is an intra-doc link. `link` should still have disambiguators
+/// if there were any.
+///
+/// The difference between this and [`should_ignore_link()`] is that this
+/// check should only be used on links that still have disambiguators.
+fn should_ignore_link_with_disambiguators(link: &str) -> bool {
+    link.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;@()".contains(ch)))
+}
+
+/// Returns true if we should ignore `path_str` due to it being unlikely
+/// that it is an intra-doc link.
+fn should_ignore_link(path_str: &str) -> bool {
+    path_str.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;".contains(ch)))
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 /// Disambiguators for a link.
 crate enum Disambiguator {

src/test/rustdoc-ui/intra-doc/email-address-localhost.rs

@@ -0,0 +1,6 @@
+#![deny(warnings)]
+
+//! Email me at <hello@localhost>.
+//~^ ERROR unknown disambiguator `hello`
+
+//! This should *not* warn: <hello@example.com>.

src/test/rustdoc-ui/intra-doc/email-address-localhost.stderr

@@ -0,0 +1,15 @@
+error: unknown disambiguator `hello`
+  --> $DIR/email-address-localhost.rs:3:18
+   |
+LL | //! Email me at <hello@localhost>.
+   |                  ^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/email-address-localhost.rs:1:9
+   |
+LL | #![deny(warnings)]
+   |         ^^^^^^^^
+   = note: `#[deny(rustdoc::broken_intra_doc_links)]` implied by `#[deny(warnings)]`
+
+error: aborting due to previous error
+

src/test/rustdoc/intra-doc/email-address.rs

@@ -0,0 +1,6 @@
+//! Email me at <hello@example.com>.
+//! Email me at <hello-world@example.com>.
+//! Email me at <hello@localhost> (this warns but will still become a link).
+// @has email_address/index.html '//a[@href="mailto:hello@example.com"]' 'hello@example.com'
+// @has email_address/index.html '//a[@href="mailto:hello-world@example.com"]' 'hello-world@example.com'
+// @has email_address/index.html '//a[@href="mailto:hello@localhost"]' 'hello@localhost'