rustc_resolve/imports.rs
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//! A bunch of methods and structures more or less related to resolving imports.
use std::cell::Cell;
use std::mem;
use rustc_ast::NodeId;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::intern::Interned;
use rustc_errors::codes::*;
use rustc_errors::{Applicability, MultiSpan, pluralize, struct_span_code_err};
use rustc_hir::def::{self, DefKind, PartialRes};
use rustc_hir::def_id::DefId;
use rustc_middle::metadata::{ModChild, Reexport};
use rustc_middle::{span_bug, ty};
use rustc_session::lint::BuiltinLintDiag;
use rustc_session::lint::builtin::{
AMBIGUOUS_GLOB_REEXPORTS, HIDDEN_GLOB_REEXPORTS, PUB_USE_OF_PRIVATE_EXTERN_CRATE,
REDUNDANT_IMPORTS, UNUSED_IMPORTS,
};
use rustc_span::Span;
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::hygiene::LocalExpnId;
use rustc_span::symbol::{Ident, Symbol, kw};
use smallvec::SmallVec;
use tracing::debug;
use crate::Determinacy::{self, *};
use crate::Namespace::*;
use crate::diagnostics::{DiagMode, Suggestion, import_candidates};
use crate::errors::{
CannotBeReexportedCratePublic, CannotBeReexportedCratePublicNS, CannotBeReexportedPrivate,
CannotBeReexportedPrivateNS, CannotDetermineImportResolution, CannotGlobImportAllCrates,
ConsiderAddingMacroExport, ConsiderMarkingAsPub, IsNotDirectlyImportable,
ItemsInTraitsAreNotImportable,
};
use crate::{
AmbiguityError, AmbiguityKind, BindingKey, Finalize, ImportSuggestion, Module,
ModuleOrUniformRoot, NameBinding, NameBindingData, NameBindingKind, ParentScope, PathResult,
PerNS, ResolutionError, Resolver, ScopeSet, Segment, Used, module_to_string, names_to_string,
};
type Res = def::Res<NodeId>;
/// Contains data for specific kinds of imports.
#[derive(Clone)]
pub(crate) enum ImportKind<'ra> {
Single {
/// `source` in `use prefix::source as target`.
source: Ident,
/// `target` in `use prefix::source as target`.
/// It will directly use `source` when the format is `use prefix::source`.
target: Ident,
/// Bindings to which `source` refers to.
source_bindings: PerNS<Cell<Result<NameBinding<'ra>, Determinacy>>>,
/// Bindings introduced by `target`.
target_bindings: PerNS<Cell<Option<NameBinding<'ra>>>>,
/// `true` for `...::{self [as target]}` imports, `false` otherwise.
type_ns_only: bool,
/// Did this import result from a nested import? ie. `use foo::{bar, baz};`
nested: bool,
/// The ID of the `UseTree` that imported this `Import`.
///
/// In the case where the `Import` was expanded from a "nested" use tree,
/// this id is the ID of the leaf tree. For example:
///
/// ```ignore (pacify the merciless tidy)
/// use foo::bar::{a, b}
/// ```
///
/// If this is the import for `foo::bar::a`, we would have the ID of the `UseTree`
/// for `a` in this field.
id: NodeId,
},
Glob {
is_prelude: bool,
// The visibility of the greatest re-export.
// n.b. `max_vis` is only used in `finalize_import` to check for re-export errors.
max_vis: Cell<Option<ty::Visibility>>,
id: NodeId,
},
ExternCrate {
source: Option<Symbol>,
target: Ident,
id: NodeId,
},
MacroUse {
/// A field has been added indicating whether it should be reported as a lint,
/// addressing issue#119301.
warn_private: bool,
},
MacroExport,
}
/// Manually implement `Debug` for `ImportKind` because the `source/target_bindings`
/// contain `Cell`s which can introduce infinite loops while printing.
impl<'ra> std::fmt::Debug for ImportKind<'ra> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
use ImportKind::*;
match self {
Single {
ref source,
ref target,
ref source_bindings,
ref target_bindings,
ref type_ns_only,
ref nested,
ref id,
} => f
.debug_struct("Single")
.field("source", source)
.field("target", target)
// Ignore the nested bindings to avoid an infinite loop while printing.
.field(
"source_bindings",
&source_bindings.clone().map(|b| b.into_inner().map(|_| format_args!(".."))),
)
.field(
"target_bindings",
&target_bindings.clone().map(|b| b.into_inner().map(|_| format_args!(".."))),
)
.field("type_ns_only", type_ns_only)
.field("nested", nested)
.field("id", id)
.finish(),
Glob { ref is_prelude, ref max_vis, ref id } => f
.debug_struct("Glob")
.field("is_prelude", is_prelude)
.field("max_vis", max_vis)
.field("id", id)
.finish(),
ExternCrate { ref source, ref target, ref id } => f
.debug_struct("ExternCrate")
.field("source", source)
.field("target", target)
.field("id", id)
.finish(),
MacroUse { .. } => f.debug_struct("MacroUse").finish(),
MacroExport => f.debug_struct("MacroExport").finish(),
}
}
}
/// One import.
#[derive(Debug, Clone)]
pub(crate) struct ImportData<'ra> {
pub kind: ImportKind<'ra>,
/// Node ID of the "root" use item -- this is always the same as `ImportKind`'s `id`
/// (if it exists) except in the case of "nested" use trees, in which case
/// it will be the ID of the root use tree. e.g., in the example
/// ```ignore (incomplete code)
/// use foo::bar::{a, b}
/// ```
/// this would be the ID of the `use foo::bar` `UseTree` node.
/// In case of imports without their own node ID it's the closest node that can be used,
/// for example, for reporting lints.
pub root_id: NodeId,
/// Span of the entire use statement.
pub use_span: Span,
/// Span of the entire use statement with attributes.
pub use_span_with_attributes: Span,
/// Did the use statement have any attributes?
pub has_attributes: bool,
/// Span of this use tree.
pub span: Span,
/// Span of the *root* use tree (see `root_id`).
pub root_span: Span,
pub parent_scope: ParentScope<'ra>,
pub module_path: Vec<Segment>,
/// The resolution of `module_path`.
pub imported_module: Cell<Option<ModuleOrUniformRoot<'ra>>>,
pub vis: ty::Visibility,
}
/// All imports are unique and allocated on a same arena,
/// so we can use referential equality to compare them.
pub(crate) type Import<'ra> = Interned<'ra, ImportData<'ra>>;
impl<'ra> ImportData<'ra> {
pub(crate) fn is_glob(&self) -> bool {
matches!(self.kind, ImportKind::Glob { .. })
}
pub(crate) fn is_nested(&self) -> bool {
match self.kind {
ImportKind::Single { nested, .. } => nested,
_ => false,
}
}
pub(crate) fn id(&self) -> Option<NodeId> {
match self.kind {
ImportKind::Single { id, .. }
| ImportKind::Glob { id, .. }
| ImportKind::ExternCrate { id, .. } => Some(id),
ImportKind::MacroUse { .. } | ImportKind::MacroExport => None,
}
}
fn simplify(&self, r: &Resolver<'_, '_>) -> Reexport {
let to_def_id = |id| r.local_def_id(id).to_def_id();
match self.kind {
ImportKind::Single { id, .. } => Reexport::Single(to_def_id(id)),
ImportKind::Glob { id, .. } => Reexport::Glob(to_def_id(id)),
ImportKind::ExternCrate { id, .. } => Reexport::ExternCrate(to_def_id(id)),
ImportKind::MacroUse { .. } => Reexport::MacroUse,
ImportKind::MacroExport => Reexport::MacroExport,
}
}
}
/// Records information about the resolution of a name in a namespace of a module.
#[derive(Clone, Default, Debug)]
pub(crate) struct NameResolution<'ra> {
/// Single imports that may define the name in the namespace.
/// Imports are arena-allocated, so it's ok to use pointers as keys.
pub single_imports: FxHashSet<Import<'ra>>,
/// The least shadowable known binding for this name, or None if there are no known bindings.
pub binding: Option<NameBinding<'ra>>,
pub shadowed_glob: Option<NameBinding<'ra>>,
}
impl<'ra> NameResolution<'ra> {
/// Returns the binding for the name if it is known or None if it not known.
pub(crate) fn binding(&self) -> Option<NameBinding<'ra>> {
self.binding.and_then(|binding| {
if !binding.is_glob_import() || self.single_imports.is_empty() {
Some(binding)
} else {
None
}
})
}
}
/// An error that may be transformed into a diagnostic later. Used to combine multiple unresolved
/// import errors within the same use tree into a single diagnostic.
#[derive(Debug, Clone)]
struct UnresolvedImportError {
span: Span,
label: Option<String>,
note: Option<String>,
suggestion: Option<Suggestion>,
candidates: Option<Vec<ImportSuggestion>>,
segment: Option<Symbol>,
/// comes from `PathRes::Failed { module }`
module: Option<DefId>,
}
// Reexports of the form `pub use foo as bar;` where `foo` is `extern crate foo;`
// are permitted for backward-compatibility under a deprecation lint.
fn pub_use_of_private_extern_crate_hack(
import: Import<'_>,
binding: NameBinding<'_>,
) -> Option<NodeId> {
match (&import.kind, &binding.kind) {
(ImportKind::Single { .. }, NameBindingKind::Import { import: binding_import, .. })
if let ImportKind::ExternCrate { id, .. } = binding_import.kind
&& import.vis.is_public() =>
{
Some(id)
}
_ => None,
}
}
impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
/// Given a binding and an import that resolves to it,
/// return the corresponding binding defined by the import.
pub(crate) fn import(
&self,
binding: NameBinding<'ra>,
import: Import<'ra>,
) -> NameBinding<'ra> {
let import_vis = import.vis.to_def_id();
let vis = if binding.vis.is_at_least(import_vis, self.tcx)
|| pub_use_of_private_extern_crate_hack(import, binding).is_some()
{
import_vis
} else {
binding.vis
};
if let ImportKind::Glob { ref max_vis, .. } = import.kind {
if vis == import_vis
|| max_vis.get().map_or(true, |max_vis| vis.is_at_least(max_vis, self.tcx))
{
max_vis.set(Some(vis.expect_local()))
}
}
self.arenas.alloc_name_binding(NameBindingData {
kind: NameBindingKind::Import { binding, import },
ambiguity: None,
warn_ambiguity: false,
span: import.span,
vis,
expansion: import.parent_scope.expansion,
})
}
/// Define the name or return the existing binding if there is a collision.
/// `update` indicates if the definition is a redefinition of an existing binding.
pub(crate) fn try_define(
&mut self,
module: Module<'ra>,
key: BindingKey,
binding: NameBinding<'ra>,
warn_ambiguity: bool,
) -> Result<(), NameBinding<'ra>> {
let res = binding.res();
self.check_reserved_macro_name(key.ident, res);
self.set_binding_parent_module(binding, module);
self.update_resolution(module, key, warn_ambiguity, |this, resolution| {
if let Some(old_binding) = resolution.binding {
if res == Res::Err && old_binding.res() != Res::Err {
// Do not override real bindings with `Res::Err`s from error recovery.
return Ok(());
}
match (old_binding.is_glob_import(), binding.is_glob_import()) {
(true, true) => {
// FIXME: remove `!binding.is_ambiguity_recursive()` after delete the warning ambiguity.
if !binding.is_ambiguity_recursive()
&& let NameBindingKind::Import { import: old_import, .. } =
old_binding.kind
&& let NameBindingKind::Import { import, .. } = binding.kind
&& old_import == import
{
// We should replace the `old_binding` with `binding` regardless
// of whether they has same resolution or not when they are
// imported from the same glob-import statement.
resolution.binding = Some(binding);
} else if res != old_binding.res() {
resolution.binding = Some(this.new_ambiguity_binding(
AmbiguityKind::GlobVsGlob,
old_binding,
binding,
warn_ambiguity,
));
} else if !old_binding.vis.is_at_least(binding.vis, this.tcx) {
// We are glob-importing the same item but with greater visibility.
resolution.binding = Some(binding);
} else if binding.is_ambiguity_recursive() {
resolution.binding = Some(this.new_warn_ambiguity_binding(binding));
}
}
(old_glob @ true, false) | (old_glob @ false, true) => {
let (glob_binding, nonglob_binding) =
if old_glob { (old_binding, binding) } else { (binding, old_binding) };
if key.ns == MacroNS
&& nonglob_binding.expansion != LocalExpnId::ROOT
&& glob_binding.res() != nonglob_binding.res()
{
resolution.binding = Some(this.new_ambiguity_binding(
AmbiguityKind::GlobVsExpanded,
nonglob_binding,
glob_binding,
false,
));
} else {
resolution.binding = Some(nonglob_binding);
}
if let Some(old_shadowed_glob) = resolution.shadowed_glob {
assert!(old_shadowed_glob.is_glob_import());
if glob_binding.res() != old_shadowed_glob.res() {
resolution.shadowed_glob = Some(this.new_ambiguity_binding(
AmbiguityKind::GlobVsGlob,
old_shadowed_glob,
glob_binding,
false,
));
} else if !old_shadowed_glob.vis.is_at_least(binding.vis, this.tcx) {
resolution.shadowed_glob = Some(glob_binding);
}
} else {
resolution.shadowed_glob = Some(glob_binding);
}
}
(false, false) => {
return Err(old_binding);
}
}
} else {
resolution.binding = Some(binding);
}
Ok(())
})
}
fn new_ambiguity_binding(
&self,
ambiguity_kind: AmbiguityKind,
primary_binding: NameBinding<'ra>,
secondary_binding: NameBinding<'ra>,
warn_ambiguity: bool,
) -> NameBinding<'ra> {
let ambiguity = Some((secondary_binding, ambiguity_kind));
let data = NameBindingData { ambiguity, warn_ambiguity, ..*primary_binding };
self.arenas.alloc_name_binding(data)
}
fn new_warn_ambiguity_binding(&self, binding: NameBinding<'ra>) -> NameBinding<'ra> {
assert!(binding.is_ambiguity_recursive());
self.arenas.alloc_name_binding(NameBindingData { warn_ambiguity: true, ..*binding })
}
// Use `f` to mutate the resolution of the name in the module.
// If the resolution becomes a success, define it in the module's glob importers.
fn update_resolution<T, F>(
&mut self,
module: Module<'ra>,
key: BindingKey,
warn_ambiguity: bool,
f: F,
) -> T
where
F: FnOnce(&mut Resolver<'ra, 'tcx>, &mut NameResolution<'ra>) -> T,
{
// Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
// during which the resolution might end up getting re-defined via a glob cycle.
let (binding, t, warn_ambiguity) = {
let resolution = &mut *self.resolution(module, key).borrow_mut();
let old_binding = resolution.binding();
let t = f(self, resolution);
if let Some(binding) = resolution.binding()
&& old_binding != Some(binding)
{
(binding, t, warn_ambiguity || old_binding.is_some())
} else {
return t;
}
};
let Ok(glob_importers) = module.glob_importers.try_borrow_mut() else {
return t;
};
// Define or update `binding` in `module`s glob importers.
for import in glob_importers.iter() {
let mut ident = key.ident;
let scope = match ident.span.reverse_glob_adjust(module.expansion, import.span) {
Some(Some(def)) => self.expn_def_scope(def),
Some(None) => import.parent_scope.module,
None => continue,
};
if self.is_accessible_from(binding.vis, scope) {
let imported_binding = self.import(binding, *import);
let key = BindingKey { ident, ..key };
let _ = self.try_define(
import.parent_scope.module,
key,
imported_binding,
warn_ambiguity,
);
}
}
t
}
// Define a dummy resolution containing a `Res::Err` as a placeholder for a failed
// or indeterminate resolution, also mark such failed imports as used to avoid duplicate diagnostics.
fn import_dummy_binding(&mut self, import: Import<'ra>, is_indeterminate: bool) {
if let ImportKind::Single { target, ref target_bindings, .. } = import.kind {
if !(is_indeterminate || target_bindings.iter().all(|binding| binding.get().is_none()))
{
return; // Has resolution, do not create the dummy binding
}
let dummy_binding = self.dummy_binding;
let dummy_binding = self.import(dummy_binding, import);
self.per_ns(|this, ns| {
let key = BindingKey::new(target, ns);
let _ = this.try_define(import.parent_scope.module, key, dummy_binding, false);
this.update_resolution(import.parent_scope.module, key, false, |_, resolution| {
resolution.single_imports.remove(&import);
})
});
self.record_use(target, dummy_binding, Used::Other);
} else if import.imported_module.get().is_none() {
self.import_use_map.insert(import, Used::Other);
if let Some(id) = import.id() {
self.used_imports.insert(id);
}
}
}
// Import resolution
//
// This is a fixed-point algorithm. We resolve imports until our efforts
// are stymied by an unresolved import; then we bail out of the current
// module and continue. We terminate successfully once no more imports
// remain or unsuccessfully when no forward progress in resolving imports
// is made.
/// Resolves all imports for the crate. This method performs the fixed-
/// point iteration.
pub(crate) fn resolve_imports(&mut self) {
let mut prev_indeterminate_count = usize::MAX;
let mut indeterminate_count = self.indeterminate_imports.len() * 3;
while indeterminate_count < prev_indeterminate_count {
prev_indeterminate_count = indeterminate_count;
indeterminate_count = 0;
for import in mem::take(&mut self.indeterminate_imports) {
let import_indeterminate_count = self.resolve_import(import);
indeterminate_count += import_indeterminate_count;
match import_indeterminate_count {
0 => self.determined_imports.push(import),
_ => self.indeterminate_imports.push(import),
}
}
}
}
pub(crate) fn finalize_imports(&mut self) {
for module in self.arenas.local_modules().iter() {
self.finalize_resolutions_in(*module);
}
let mut seen_spans = FxHashSet::default();
let mut errors = vec![];
let mut prev_root_id: NodeId = NodeId::ZERO;
let determined_imports = mem::take(&mut self.determined_imports);
let indeterminate_imports = mem::take(&mut self.indeterminate_imports);
let mut glob_error = false;
for (is_indeterminate, import) in determined_imports
.iter()
.map(|i| (false, i))
.chain(indeterminate_imports.iter().map(|i| (true, i)))
{
let unresolved_import_error = self.finalize_import(*import);
// If this import is unresolved then create a dummy import
// resolution for it so that later resolve stages won't complain.
self.import_dummy_binding(*import, is_indeterminate);
if let Some(err) = unresolved_import_error {
glob_error |= import.is_glob();
if let ImportKind::Single { source, ref source_bindings, .. } = import.kind {
if source.name == kw::SelfLower {
// Silence `unresolved import` error if E0429 is already emitted
if let Err(Determined) = source_bindings.value_ns.get() {
continue;
}
}
}
if prev_root_id != NodeId::ZERO
&& prev_root_id != import.root_id
&& !errors.is_empty()
{
// In the case of a new import line, throw a diagnostic message
// for the previous line.
self.throw_unresolved_import_error(errors, glob_error);
errors = vec![];
}
if seen_spans.insert(err.span) {
errors.push((*import, err));
prev_root_id = import.root_id;
}
}
}
if !errors.is_empty() {
self.throw_unresolved_import_error(errors, glob_error);
return;
}
for import in &indeterminate_imports {
let path = import_path_to_string(
&import.module_path.iter().map(|seg| seg.ident).collect::<Vec<_>>(),
&import.kind,
import.span,
);
// FIXME: there should be a better way of doing this than
// formatting this as a string then checking for `::`
if path.contains("::") {
let err = UnresolvedImportError {
span: import.span,
label: None,
note: None,
suggestion: None,
candidates: None,
segment: None,
module: None,
};
errors.push((*import, err))
}
}
self.throw_unresolved_import_error(errors, glob_error);
}
pub(crate) fn check_hidden_glob_reexports(
&mut self,
exported_ambiguities: FxHashSet<NameBinding<'ra>>,
) {
for module in self.arenas.local_modules().iter() {
for (key, resolution) in self.resolutions(*module).borrow().iter() {
let resolution = resolution.borrow();
if let Some(binding) = resolution.binding {
if let NameBindingKind::Import { import, .. } = binding.kind
&& let Some((amb_binding, _)) = binding.ambiguity
&& binding.res() != Res::Err
&& exported_ambiguities.contains(&binding)
{
self.lint_buffer.buffer_lint(
AMBIGUOUS_GLOB_REEXPORTS,
import.root_id,
import.root_span,
BuiltinLintDiag::AmbiguousGlobReexports {
name: key.ident.to_string(),
namespace: key.ns.descr().to_string(),
first_reexport_span: import.root_span,
duplicate_reexport_span: amb_binding.span,
},
);
}
if let Some(glob_binding) = resolution.shadowed_glob {
let binding_id = match binding.kind {
NameBindingKind::Res(res) => {
Some(self.def_id_to_node_id[res.def_id().expect_local()])
}
NameBindingKind::Module(module) => {
Some(self.def_id_to_node_id[module.def_id().expect_local()])
}
NameBindingKind::Import { import, .. } => import.id(),
};
if binding.res() != Res::Err
&& glob_binding.res() != Res::Err
&& let NameBindingKind::Import { import: glob_import, .. } =
glob_binding.kind
&& let Some(binding_id) = binding_id
&& let Some(glob_import_id) = glob_import.id()
&& let glob_import_def_id = self.local_def_id(glob_import_id)
&& self.effective_visibilities.is_exported(glob_import_def_id)
&& glob_binding.vis.is_public()
&& !binding.vis.is_public()
{
self.lint_buffer.buffer_lint(
HIDDEN_GLOB_REEXPORTS,
binding_id,
binding.span,
BuiltinLintDiag::HiddenGlobReexports {
name: key.ident.name.to_string(),
namespace: key.ns.descr().to_owned(),
glob_reexport_span: glob_binding.span,
private_item_span: binding.span,
},
);
}
}
}
}
}
}
fn throw_unresolved_import_error(
&mut self,
errors: Vec<(Import<'_>, UnresolvedImportError)>,
glob_error: bool,
) {
if errors.is_empty() {
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)| {
let path = import_path_to_string(
&import.module_path.iter().map(|seg| seg.ident).collect::<Vec<_>>(),
&import.kind,
err.span,
);
format!("`{path}`")
})
.collect::<Vec<_>>();
let msg = format!("unresolved import{} {}", pluralize!(paths.len()), paths.join(", "),);
let mut diag = struct_span_code_err!(self.dcx(), span, E0432, "{msg}");
if let Some((_, UnresolvedImportError { note: Some(note), .. })) = errors.iter().last() {
diag.note(note.clone());
}
for (import, err) in errors.into_iter().take(MAX_LABEL_COUNT) {
if let Some(label) = err.label {
diag.span_label(err.span, label);
}
if let Some((suggestions, msg, applicability)) = err.suggestion {
if suggestions.is_empty() {
diag.help(msg);
continue;
}
diag.multipart_suggestion(msg, suggestions, applicability);
}
if let Some(candidates) = &err.candidates {
match &import.kind {
ImportKind::Single { nested: false, source, target, .. } => import_candidates(
self.tcx,
&mut diag,
Some(err.span),
candidates,
DiagMode::Import { append: false },
(source != target)
.then(|| format!(" as {target}"))
.as_deref()
.unwrap_or(""),
),
ImportKind::Single { nested: true, source, target, .. } => {
import_candidates(
self.tcx,
&mut diag,
None,
candidates,
DiagMode::Normal,
(source != target)
.then(|| format!(" as {target}"))
.as_deref()
.unwrap_or(""),
);
}
_ => {}
}
}
if matches!(import.kind, ImportKind::Single { .. })
&& let Some(segment) = err.segment
&& let Some(module) = err.module
{
self.find_cfg_stripped(&mut diag, &segment, module)
}
}
let guar = diag.emit();
if glob_error {
self.glob_error = Some(guar);
}
}
/// Attempts to resolve the given import, returning:
/// - `0` means its resolution is determined.
/// - Other values mean that indeterminate exists under certain namespaces.
///
/// Meanwhile, if resolve successful, the resolved bindings are written
/// into the module.
fn resolve_import(&mut self, import: Import<'ra>) -> usize {
debug!(
"(resolving import for module) resolving import `{}::...` in `{}`",
Segment::names_to_string(&import.module_path),
module_to_string(import.parent_scope.module).unwrap_or_else(|| "???".to_string()),
);
let module = if let Some(module) = import.imported_module.get() {
module
} else {
let path_res = self.maybe_resolve_path(
&import.module_path,
None,
&import.parent_scope,
Some(import),
);
match path_res {
PathResult::Module(module) => module,
PathResult::Indeterminate => return 3,
PathResult::NonModule(..) | PathResult::Failed { .. } => return 0,
}
};
import.imported_module.set(Some(module));
let (source, target, source_bindings, target_bindings, type_ns_only) = match import.kind {
ImportKind::Single {
source,
target,
ref source_bindings,
ref target_bindings,
type_ns_only,
..
} => (source, target, source_bindings, target_bindings, type_ns_only),
ImportKind::Glob { .. } => {
self.resolve_glob_import(import);
return 0;
}
_ => unreachable!(),
};
let mut indeterminate_count = 0;
self.per_ns(|this, ns| {
if !type_ns_only || ns == TypeNS {
if let Err(Undetermined) = source_bindings[ns].get() {
let binding = this.maybe_resolve_ident_in_module(
module,
source,
ns,
&import.parent_scope,
Some(import),
);
source_bindings[ns].set(binding);
} else {
return;
};
let parent = import.parent_scope.module;
match source_bindings[ns].get() {
Err(Undetermined) => indeterminate_count += 1,
// Don't update the resolution, because it was never added.
Err(Determined) if target.name == kw::Underscore => {}
Ok(binding) if binding.is_importable() => {
let imported_binding = this.import(binding, import);
target_bindings[ns].set(Some(imported_binding));
this.define(parent, target, ns, imported_binding);
}
source_binding @ (Ok(..) | Err(Determined)) => {
if source_binding.is_ok() {
this.dcx()
.create_err(IsNotDirectlyImportable { span: import.span, target })
.emit();
}
let key = BindingKey::new(target, ns);
this.update_resolution(parent, key, false, |_, resolution| {
resolution.single_imports.remove(&import);
});
}
}
}
});
indeterminate_count
}
/// Performs final import resolution, consistency checks and error reporting.
///
/// Optionally returns an unresolved import error. This error is buffered and used to
/// consolidate multiple unresolved import errors into a single diagnostic.
fn finalize_import(&mut self, import: Import<'ra>) -> Option<UnresolvedImportError> {
let ignore_binding = match &import.kind {
ImportKind::Single { target_bindings, .. } => target_bindings[TypeNS].get(),
_ => None,
};
let ambiguity_errors_len =
|errors: &Vec<AmbiguityError<'_>>| errors.iter().filter(|error| !error.warning).count();
let prev_ambiguity_errors_len = ambiguity_errors_len(&self.ambiguity_errors);
let finalize = Finalize::with_root_span(import.root_id, import.span, import.root_span);
// We'll provide more context to the privacy errors later, up to `len`.
let privacy_errors_len = self.privacy_errors.len();
let path_res = self.resolve_path(
&import.module_path,
None,
&import.parent_scope,
Some(finalize),
ignore_binding,
Some(import),
);
let no_ambiguity =
ambiguity_errors_len(&self.ambiguity_errors) == prev_ambiguity_errors_len;
let module = match path_res {
PathResult::Module(module) => {
// Consistency checks, analogous to `finalize_macro_resolutions`.
if let Some(initial_module) = import.imported_module.get() {
if module != initial_module && no_ambiguity {
span_bug!(import.span, "inconsistent resolution for an import");
}
} else if self.privacy_errors.is_empty() {
self.dcx()
.create_err(CannotDetermineImportResolution { span: import.span })
.emit();
}
module
}
PathResult::Failed {
is_error_from_last_segment: false,
span,
segment_name,
label,
suggestion,
module,
} => {
if no_ambiguity {
assert!(import.imported_module.get().is_none());
self.report_error(span, ResolutionError::FailedToResolve {
segment: Some(segment_name),
label,
suggestion,
module,
});
}
return None;
}
PathResult::Failed {
is_error_from_last_segment: true,
span,
label,
suggestion,
module,
segment_name,
..
} => {
if no_ambiguity {
assert!(import.imported_module.get().is_none());
let module = if let Some(ModuleOrUniformRoot::Module(m)) = module {
m.opt_def_id()
} else {
None
};
let err = match self.make_path_suggestion(
span,
import.module_path.clone(),
&import.parent_scope,
) {
Some((suggestion, note)) => UnresolvedImportError {
span,
label: None,
note,
suggestion: Some((
vec![(span, Segment::names_to_string(&suggestion))],
String::from("a similar path exists"),
Applicability::MaybeIncorrect,
)),
candidates: None,
segment: Some(segment_name),
module,
},
None => UnresolvedImportError {
span,
label: Some(label),
note: None,
suggestion,
candidates: None,
segment: Some(segment_name),
module,
},
};
return Some(err);
}
return None;
}
PathResult::NonModule(partial_res) => {
if no_ambiguity && partial_res.full_res() != Some(Res::Err) {
// Check if there are no ambiguities and the result is not dummy.
assert!(import.imported_module.get().is_none());
}
// The error was already reported earlier.
return None;
}
PathResult::Indeterminate => unreachable!(),
};
let (ident, target, source_bindings, target_bindings, type_ns_only, import_id) =
match import.kind {
ImportKind::Single {
source,
target,
ref source_bindings,
ref target_bindings,
type_ns_only,
id,
..
} => (source, target, source_bindings, target_bindings, type_ns_only, id),
ImportKind::Glob { is_prelude, ref max_vis, id } => {
if import.module_path.len() <= 1 {
// HACK(eddyb) `lint_if_path_starts_with_module` needs at least
// 2 segments, so the `resolve_path` above won't trigger it.
let mut full_path = import.module_path.clone();
full_path.push(Segment::from_ident(Ident::empty()));
self.lint_if_path_starts_with_module(Some(finalize), &full_path, None);
}
if let ModuleOrUniformRoot::Module(module) = module {
if module == import.parent_scope.module {
// Importing a module into itself is not allowed.
return Some(UnresolvedImportError {
span: import.span,
label: Some(String::from(
"cannot glob-import a module into itself",
)),
note: None,
suggestion: None,
candidates: None,
segment: None,
module: None,
});
}
}
if !is_prelude
&& let Some(max_vis) = max_vis.get()
&& !max_vis.is_at_least(import.vis, self.tcx)
{
let def_id = self.local_def_id(id);
self.lint_buffer.buffer_lint(
UNUSED_IMPORTS,
id,
import.span,
BuiltinLintDiag::RedundantImportVisibility {
max_vis: max_vis.to_string(def_id, self.tcx),
import_vis: import.vis.to_string(def_id, self.tcx),
span: import.span,
},
);
}
return None;
}
_ => unreachable!(),
};
if self.privacy_errors.len() != privacy_errors_len {
// Get the Res for the last element, so that we can point to alternative ways of
// importing it if available.
let mut path = import.module_path.clone();
path.push(Segment::from_ident(ident));
if let PathResult::Module(ModuleOrUniformRoot::Module(module)) = self.resolve_path(
&path,
None,
&import.parent_scope,
Some(finalize),
ignore_binding,
None,
) {
let res = module.res().map(|r| (r, ident));
for error in &mut self.privacy_errors[privacy_errors_len..] {
error.outermost_res = res;
}
}
}
let mut all_ns_err = true;
self.per_ns(|this, ns| {
if !type_ns_only || ns == TypeNS {
let binding = this.resolve_ident_in_module(
module,
ident,
ns,
&import.parent_scope,
Some(Finalize { report_private: false, ..finalize }),
target_bindings[ns].get(),
Some(import),
);
match binding {
Ok(binding) => {
// Consistency checks, analogous to `finalize_macro_resolutions`.
let initial_res = source_bindings[ns].get().map(|initial_binding| {
all_ns_err = false;
if let Some(target_binding) = target_bindings[ns].get() {
if target.name == kw::Underscore
&& initial_binding.is_extern_crate()
&& !initial_binding.is_import()
{
let used = if import.module_path.is_empty() {
Used::Scope
} else {
Used::Other
};
this.record_use(ident, target_binding, used);
}
}
initial_binding.res()
});
let res = binding.res();
let has_ambiguity_error =
this.ambiguity_errors.iter().any(|error| !error.warning);
if res == Res::Err || has_ambiguity_error {
this.dcx()
.span_delayed_bug(import.span, "some error happened for an import");
return;
}
if let Ok(initial_res) = initial_res {
if res != initial_res {
span_bug!(import.span, "inconsistent resolution for an import");
}
} else if this.privacy_errors.is_empty() {
this.dcx()
.create_err(CannotDetermineImportResolution { span: import.span })
.emit();
}
}
Err(..) => {
// FIXME: This assert may fire if public glob is later shadowed by a private
// single import (see test `issue-55884-2.rs`). In theory single imports should
// always block globs, even if they are not yet resolved, so that this kind of
// self-inconsistent resolution never happens.
// Re-enable the assert when the issue is fixed.
// assert!(result[ns].get().is_err());
}
}
}
});
if all_ns_err {
let mut all_ns_failed = true;
self.per_ns(|this, ns| {
if !type_ns_only || ns == TypeNS {
let binding = this.resolve_ident_in_module(
module,
ident,
ns,
&import.parent_scope,
Some(finalize),
None,
None,
);
if binding.is_ok() {
all_ns_failed = false;
}
}
});
return if all_ns_failed {
let resolutions = match module {
ModuleOrUniformRoot::Module(module) => Some(self.resolutions(module).borrow()),
_ => None,
};
let resolutions = resolutions.as_ref().into_iter().flat_map(|r| r.iter());
let names = resolutions
.filter_map(|(BindingKey { ident: i, .. }, resolution)| {
if i.name == ident.name {
return None;
} // Never suggest the same name
match *resolution.borrow() {
NameResolution { binding: Some(name_binding), .. } => {
match name_binding.kind {
NameBindingKind::Import { binding, .. } => {
match binding.kind {
// Never suggest the name that has binding error
// i.e., the name that cannot be previously resolved
NameBindingKind::Res(Res::Err) => None,
_ => Some(i.name),
}
}
_ => Some(i.name),
}
}
NameResolution { ref single_imports, .. }
if single_imports.is_empty() =>
{
None
}
_ => Some(i.name),
}
})
.collect::<Vec<Symbol>>();
let lev_suggestion =
find_best_match_for_name(&names, ident.name, None).map(|suggestion| {
(
vec![(ident.span, suggestion.to_string())],
String::from("a similar name exists in the module"),
Applicability::MaybeIncorrect,
)
});
let (suggestion, note) =
match self.check_for_module_export_macro(import, module, ident) {
Some((suggestion, note)) => (suggestion.or(lev_suggestion), note),
_ => (lev_suggestion, None),
};
let label = match module {
ModuleOrUniformRoot::Module(module) => {
let module_str = module_to_string(module);
if let Some(module_str) = module_str {
format!("no `{ident}` in `{module_str}`")
} else {
format!("no `{ident}` in the root")
}
}
_ => {
if !ident.is_path_segment_keyword() {
format!("no external crate `{ident}`")
} else {
// HACK(eddyb) this shows up for `self` & `super`, which
// should work instead - for now keep the same error message.
format!("no `{ident}` in the root")
}
}
};
let parent_suggestion =
self.lookup_import_candidates(ident, TypeNS, &import.parent_scope, |_| true);
Some(UnresolvedImportError {
span: import.span,
label: Some(label),
note,
suggestion,
candidates: if !parent_suggestion.is_empty() {
Some(parent_suggestion)
} else {
None
},
module: import.imported_module.get().and_then(|module| {
if let ModuleOrUniformRoot::Module(m) = module {
m.opt_def_id()
} else {
None
}
}),
segment: Some(ident.name),
})
} else {
// `resolve_ident_in_module` reported a privacy error.
None
};
}
let mut reexport_error = None;
let mut any_successful_reexport = false;
let mut crate_private_reexport = false;
self.per_ns(|this, ns| {
if let Ok(binding) = source_bindings[ns].get() {
if !binding.vis.is_at_least(import.vis, this.tcx) {
reexport_error = Some((ns, binding));
if let ty::Visibility::Restricted(binding_def_id) = binding.vis {
if binding_def_id.is_top_level_module() {
crate_private_reexport = true;
}
}
} else {
any_successful_reexport = true;
}
}
});
// All namespaces must be re-exported with extra visibility for an error to occur.
if !any_successful_reexport {
let (ns, binding) = reexport_error.unwrap();
if let Some(extern_crate_id) = pub_use_of_private_extern_crate_hack(import, binding) {
self.lint_buffer.buffer_lint(
PUB_USE_OF_PRIVATE_EXTERN_CRATE,
import_id,
import.span,
BuiltinLintDiag::PrivateExternCrateReexport {
source: ident,
extern_crate_span: self.tcx.source_span(self.local_def_id(extern_crate_id)),
},
);
} else if ns == TypeNS {
let err = if crate_private_reexport {
self.dcx()
.create_err(CannotBeReexportedCratePublicNS { span: import.span, ident })
} else {
self.dcx().create_err(CannotBeReexportedPrivateNS { span: import.span, ident })
};
err.emit();
} else {
let mut err = if crate_private_reexport {
self.dcx()
.create_err(CannotBeReexportedCratePublic { span: import.span, ident })
} else {
self.dcx().create_err(CannotBeReexportedPrivate { span: import.span, ident })
};
match binding.kind {
NameBindingKind::Res(Res::Def(DefKind::Macro(_), def_id))
// exclude decl_macro
if self.get_macro_by_def_id(def_id).macro_rules =>
{
err.subdiagnostic( ConsiderAddingMacroExport {
span: binding.span,
});
}
_ => {
err.subdiagnostic( ConsiderMarkingAsPub {
span: import.span,
ident,
});
}
}
err.emit();
}
}
if import.module_path.len() <= 1 {
// HACK(eddyb) `lint_if_path_starts_with_module` needs at least
// 2 segments, so the `resolve_path` above won't trigger it.
let mut full_path = import.module_path.clone();
full_path.push(Segment::from_ident(ident));
self.per_ns(|this, ns| {
if let Ok(binding) = source_bindings[ns].get() {
this.lint_if_path_starts_with_module(Some(finalize), &full_path, Some(binding));
}
});
}
// Record what this import resolves to for later uses in documentation,
// this may resolve to either a value or a type, but for documentation
// purposes it's good enough to just favor one over the other.
self.per_ns(|this, ns| {
if let Ok(binding) = source_bindings[ns].get() {
this.import_res_map.entry(import_id).or_default()[ns] = Some(binding.res());
}
});
debug!("(resolving single import) successfully resolved import");
None
}
pub(crate) fn check_for_redundant_imports(&mut self, import: Import<'ra>) -> bool {
// This function is only called for single imports.
let ImportKind::Single {
source, target, ref source_bindings, ref target_bindings, id, ..
} = import.kind
else {
unreachable!()
};
// Skip if the import is of the form `use source as target` and source != target.
if source != target {
return false;
}
// Skip if the import was produced by a macro.
if import.parent_scope.expansion != LocalExpnId::ROOT {
return false;
}
// Skip if we are inside a named module (in contrast to an anonymous
// module defined by a block).
// Skip if the import is public or was used through non scope-based resolution,
// e.g. through a module-relative path.
if self.import_use_map.get(&import) == Some(&Used::Other)
|| self.effective_visibilities.is_exported(self.local_def_id(id))
{
return false;
}
let mut is_redundant = true;
let mut redundant_span = PerNS { value_ns: None, type_ns: None, macro_ns: None };
self.per_ns(|this, ns| {
if is_redundant && let Ok(binding) = source_bindings[ns].get() {
if binding.res() == Res::Err {
return;
}
match this.early_resolve_ident_in_lexical_scope(
target,
ScopeSet::All(ns),
&import.parent_scope,
None,
false,
target_bindings[ns].get(),
None,
) {
Ok(other_binding) => {
is_redundant = binding.res() == other_binding.res()
&& !other_binding.is_ambiguity_recursive();
if is_redundant {
redundant_span[ns] =
Some((other_binding.span, other_binding.is_import()));
}
}
Err(_) => is_redundant = false,
}
}
});
if is_redundant && !redundant_span.is_empty() {
let mut redundant_spans: Vec<_> = redundant_span.present_items().collect();
redundant_spans.sort();
redundant_spans.dedup();
self.lint_buffer.buffer_lint(
REDUNDANT_IMPORTS,
id,
import.span,
BuiltinLintDiag::RedundantImport(redundant_spans, source),
);
return true;
}
false
}
fn resolve_glob_import(&mut self, import: Import<'ra>) {
// This function is only called for glob imports.
let ImportKind::Glob { id, is_prelude, .. } = import.kind else { unreachable!() };
let ModuleOrUniformRoot::Module(module) = import.imported_module.get().unwrap() else {
self.dcx().emit_err(CannotGlobImportAllCrates { span: import.span });
return;
};
if module.is_trait() {
self.dcx().emit_err(ItemsInTraitsAreNotImportable { span: import.span });
return;
} else if module == import.parent_scope.module {
return;
} else if is_prelude {
self.prelude = Some(module);
return;
}
// Add to module's glob_importers
module.glob_importers.borrow_mut().push(import);
// Ensure that `resolutions` isn't borrowed during `try_define`,
// since it might get updated via a glob cycle.
let bindings = self
.resolutions(module)
.borrow()
.iter()
.filter_map(|(key, resolution)| {
resolution.borrow().binding().map(|binding| (*key, binding))
})
.collect::<Vec<_>>();
for (mut key, binding) in bindings {
let scope = match key.ident.span.reverse_glob_adjust(module.expansion, import.span) {
Some(Some(def)) => self.expn_def_scope(def),
Some(None) => import.parent_scope.module,
None => continue,
};
if self.is_accessible_from(binding.vis, scope) {
let imported_binding = self.import(binding, import);
let warn_ambiguity = self
.resolution(import.parent_scope.module, key)
.borrow()
.binding()
.is_some_and(|binding| binding.warn_ambiguity_recursive());
let _ = self.try_define(
import.parent_scope.module,
key,
imported_binding,
warn_ambiguity,
);
}
}
// Record the destination of this import
self.record_partial_res(id, PartialRes::new(module.res().unwrap()));
}
// Miscellaneous post-processing, including recording re-exports,
// reporting conflicts, and reporting unresolved imports.
fn finalize_resolutions_in(&mut self, module: Module<'ra>) {
// Since import resolution is finished, globs will not define any more names.
*module.globs.borrow_mut() = Vec::new();
if let Some(def_id) = module.opt_def_id() {
let mut children = Vec::new();
module.for_each_child(self, |this, ident, _, binding| {
let res = binding.res().expect_non_local();
let error_ambiguity = binding.is_ambiguity_recursive() && !binding.warn_ambiguity;
if res != def::Res::Err && !error_ambiguity {
let mut reexport_chain = SmallVec::new();
let mut next_binding = binding;
while let NameBindingKind::Import { binding, import, .. } = next_binding.kind {
reexport_chain.push(import.simplify(this));
next_binding = binding;
}
children.push(ModChild { ident, res, vis: binding.vis, reexport_chain });
}
});
if !children.is_empty() {
// Should be fine because this code is only called for local modules.
self.module_children.insert(def_id.expect_local(), children);
}
}
}
}
fn import_path_to_string(names: &[Ident], import_kind: &ImportKind<'_>, span: Span) -> String {
let pos = names.iter().position(|p| span == p.span && p.name != kw::PathRoot);
let global = !names.is_empty() && names[0].name == kw::PathRoot;
if let Some(pos) = pos {
let names = if global { &names[1..pos + 1] } else { &names[..pos + 1] };
names_to_string(&names.iter().map(|ident| ident.name).collect::<Vec<_>>())
} else {
let names = if global { &names[1..] } else { names };
if names.is_empty() {
import_kind_to_string(import_kind)
} else {
format!(
"{}::{}",
names_to_string(&names.iter().map(|ident| ident.name).collect::<Vec<_>>()),
import_kind_to_string(import_kind),
)
}
}
}
fn import_kind_to_string(import_kind: &ImportKind<'_>) -> String {
match import_kind {
ImportKind::Single { source, .. } => source.to_string(),
ImportKind::Glob { .. } => "*".to_string(),
ImportKind::ExternCrate { .. } => "<extern crate>".to_string(),
ImportKind::MacroUse { .. } => "#[macro_use]".to_string(),
ImportKind::MacroExport => "#[macro_export]".to_string(),
}
}