Emit a single error when importing a path with `_`

When encountering `use _;`, `use _::*'` or similar, do not emit two errors for that single mistake. This also side-steps the issue of resolve errors suggesting adding a crate named `_` to `Cargo.toml`.

1 files changed, 14 insertions, 4 deletions

diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index e989209e177..1b7a2c3bda0 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -608,7 +608,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             }
         }
 
-        self.throw_unresolved_import_error(errors, glob_error);
+        if !errors.is_empty() {
+            self.throw_unresolved_import_error(errors, glob_error);
+        }
     }
 
     pub(crate) fn check_hidden_glob_reexports(
@@ -688,14 +690,19 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             Some(def_id) if self.mods_with_parse_errors.contains(&def_id) => false,
             _ => true,
         });
+        errors.retain(|(_import, err)| {
+            // If we've encountered something like `use _;`, we've already emitted an error stating
+            // that `_` is not a valid identifier, so we ignore that resolve error.
+            err.segment != Some(kw::Underscore)
+        });
+
         if errors.is_empty() {
+            self.tcx.dcx().delayed_bug("expected a parse or \"`_` can't be an identifier\" error");
             return;
         }
 
-        /// Upper limit on the number of `span_label` messages.
-        const MAX_LABEL_COUNT: usize = 10;
-
         let span = MultiSpan::from_spans(errors.iter().map(|(_, err)| err.span).collect());
+
         let paths = errors
             .iter()
             .map(|(import, err)| {
@@ -715,6 +722,9 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             diag.note(note.clone());
         }
 
+        /// Upper limit on the number of `span_label` messages.
+        const MAX_LABEL_COUNT: usize = 10;
+
         for (import, err) in errors.into_iter().take(MAX_LABEL_COUNT) {
             if let Some(label) = err.label {
                 diag.span_label(err.span, label);