Silence some resolve errors when there have been glob import errors

When encountering `use foo::*;` where `foo` fails to be found, and we later
encounter resolution errors, we silence those later errors.

A single case of the above, for an *existing* import on a big codebase would
otherwise have a huge number of knock-down spurious errors.

Ideally, instead of a global flag to silence all subsequent resolve errors,
we'd want to introduce an unameable binding in the appropriate rib as a
sentinel when there's a failed glob import, so when we encounter a resolve
error we can search for that sentinel and if found, and only then, silence
that error. The current approach is just a quick proof of concept to
iterate over.

Partially address #96799.

compiler/rustc_resolve/src/lib.rs

@@ -37,7 +37,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::{FreezeReadGuard, Lrc};
-use rustc_errors::{Applicability, Diag, ErrCode};
+use rustc_errors::{Applicability, Diag, ErrCode, ErrorGuaranteed};
 use rustc_expand::base::{DeriveResolution, SyntaxExtension, SyntaxExtensionKind};
 use rustc_feature::BUILTIN_ATTRIBUTES;
 use rustc_hir::def::Namespace::{self, *};
@@ -1052,6 +1052,7 @@ pub struct Resolver<'a, 'tcx> {
 
     /// Maps glob imports to the names of items actually imported.
     glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
+    glob_error: Option<ErrorGuaranteed>,
     visibilities_for_hashing: Vec<(LocalDefId, ty::Visibility)>,
     used_imports: FxHashSet<NodeId>,
     maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
@@ -1421,6 +1422,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             ast_transform_scopes: FxHashMap::default(),
 
             glob_map: Default::default(),
+            glob_error: None,
             visibilities_for_hashing: Default::default(),
             used_imports: FxHashSet::default(),
             maybe_unused_trait_imports: Default::default(),