resolve: mark it undetermined if single import is not has any bindings

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -355,6 +355,7 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
  parent_scope: self.parent_scope,
  module_path,
  imported_module: Cell::new(None),
+ indeterminate: Cell::new(true),
  span,
  use_span: item.span,
  use_span_with_attributes: item.span_with_attributes(),
@@ -869,6 +870,7 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
  root_id: item.id,
  parent_scope: self.parent_scope,
  imported_module: Cell::new(module),
+ indeterminate: Cell::new(true),
  has_attributes: !item.attrs.is_empty(),
  use_span_with_attributes: item.span_with_attributes(),
  use_span: item.span,
@@ -1070,6 +1072,7 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
  root_id: item.id,
  parent_scope: this.parent_scope,
  imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
+ indeterminate: Cell::new(false),
  use_span_with_attributes: item.span_with_attributes(),
  has_attributes: !item.attrs.is_empty(),
  use_span: item.span,
@@ -1234,6 +1237,7 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
  root_id: item.id,
  parent_scope: self.parent_scope,
  imported_module: Cell::new(None),
+ indeterminate: Cell::new(true),
  has_attributes: false,
  use_span_with_attributes: span,
  use_span: span,

compiler/rustc_resolve/src/ident.rs

@@ -967,6 +967,21 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
  // if it can then our result is not determined and can be invalidated.
  for single_import in &resolution.single_imports {
  let Some(import_vis) = single_import.vis.get() else {
+ // This branch handles a cycle in single imports, which occurs
+ // when we've previously captured the `vis` value during an import
+ // process.
+ //
+ // For example:
+ // ```
+ // use a::b;
+ // use b as a;
+ // ```
+ // 1. Steal the `vis` in `use a::b` and attempt to locate `a` in the
+ // current module.
+ // 2. Encounter the import `use b as a`, which is a `single_import` for `a`,
+ // and try to find `b` in the current module.
+ // 3. Re-encounter the `use a::b` import since it's a `single_import` of `b`.
+ // This leads to entering this branch.
  continue;
  };
  if !self.is_accessible_from(import_vis, parent_scope.module) {
@@ -981,6 +996,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
  // named imports.
  continue;
  }
+
+ if single_import.indeterminate.get() {
+ return Err((Undetermined, Weak::No));
+ }
  let Some(module) = single_import.imported_module.get() else {
  return Err((Undetermined, Weak::No));
  };

compiler/rustc_resolve/src/imports.rs

@@ -173,6 +173,8 @@ pub(crate) struct ImportData<'a> {
  pub module_path: Vec<Segment>,
  /// The resolution of `module_path`.
  pub imported_module: Cell<Option<ModuleOrUniformRoot<'a>>>,
+ /// `true` if this import is indeterminate in all namespaces.
+ pub indeterminate: Cell<bool>,
  pub vis: Cell<Option<ty::Visibility>>,
  pub used: Cell<Option<Used>>,
 }
@@ -351,9 +353,9 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
  (old_glob @ true, false) | (old_glob @ false, true) => {
  let (glob_binding, nonglob_binding) =
  if old_glob { (old_binding, binding) } else { (binding, old_binding) };
- if glob_binding.res() != nonglob_binding.res()
- && key.ns == MacroNS
+ if key.ns == MacroNS
  && nonglob_binding.expansion != LocalExpnId::ROOT
+ && glob_binding.res() != nonglob_binding.res()
  {
  resolution.binding = Some(this.ambiguity(
  AmbiguityKind::GlobVsExpanded,
@@ -794,6 +796,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
  ..
  } => (source, target, source_bindings, target_bindings, type_ns_only),
  ImportKind::Glob { .. } => {
+ import.indeterminate.set(false);
  self.resolve_glob_import(import);
  return 0;
  }
@@ -844,6 +847,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
  }
  });
 
+ if indeterminate_count < 3 {
+ import.indeterminate.set(false);
+ }
+
  indeterminate_count
  }
 

tests/ui/imports/import-loop-2.stderr

@@ -1,8 +1,8 @@
-error[E0432]: unresolved import `a::x`
- --> $DIR/import-loop-2.rs:8:13
+error[E0432]: unresolved import `b::x`
+ --> $DIR/import-loop-2.rs:4:13
  |
-LL | pub use a::x;
- | ^^^^ no `x` in `a`
+LL | pub use b::x;
+ | ^^^^ no `x` in `b`
 
 error: aborting due to 1 previous error
 

tests/ui/imports/import4.stderr

@@ -1,8 +1,8 @@
-error[E0432]: unresolved import `a::foo`
- --> $DIR/import4.rs:5:17
+error[E0432]: unresolved import `b::foo`
+ --> $DIR/import4.rs:4:17
  |
-LL | mod b { pub use a::foo; }
- | ^^^^^^ no `foo` in `a`
+LL | mod a { pub use b::foo; }
+ | ^^^^^^ no `foo` in `b`
 
 error: aborting due to 1 previous error
 

tests/ui/imports/shadow-glob-module-resolution.rs

@@ -0,0 +1,17 @@
+// https:/rust-lang/rust/issues/124490
+
+mod a {
+ pub mod b {
+ pub mod c {}
+ }
+}
+
+use a::*;
+
+use b::c;
+//~^ ERROR: cannot determine resolution for the import
+//~| ERROR: cannot determine resolution for the import
+//~| ERROR: unresolved import `b::c`
+use c as b;
+
+fn main() {}

tests/ui/imports/shadow-glob-module-resolution.stderr

@@ -0,0 +1,23 @@
+error: cannot determine resolution for the import
+ --> $DIR/shadow-glob-module-resolution.rs:11:5
+ |
+LL | use b::c;
+ | ^^^^
+
+error: cannot determine resolution for the import
+ --> $DIR/shadow-glob-module-resolution.rs:11:5
+ |
+LL | use b::c;
+ | ^^^^
+ |
+ = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0432]: unresolved import `b::c`
+ --> $DIR/shadow-glob-module-resolution.rs:11:5
+ |
+LL | use b::c;
+ | ^^^^
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0432`.