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Move the unused extern crate check back to the resolver.

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This commit is contained in:
Camille GILLOT 2023-02-22 20:25:10 +00:00
parent b869e84e58
commit 958419d354
8 changed files with 190 additions and 169 deletions
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133
compiler/rustc_hir_analysis/src/check_unused.rs
View File

@ -1,12 +1,8 @@
use crate::errors::{ExternCrateNotIdiomatic, UnusedExternCrate};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::unord::UnordSet;
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::def_id::LocalDefId;
use rustc_middle::ty::TyCtxt;
use rustc_session::lint;
use rustc_span::{Span, Symbol};
pub fn check_crate(tcx: TyCtxt<'_>) {
let mut used_trait_imports: UnordSet<LocalDefId> = Default::default();
@ -43,131 +39,4 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
|lint| lint,
);
}
unused_crates_lint(tcx);
}
fn unused_crates_lint(tcx: TyCtxt<'_>) {
let lint = lint::builtin::UNUSED_EXTERN_CRATES;
// Collect first the crates that are completely unused. These we
// can always suggest removing (no matter which edition we are
// in).
let unused_extern_crates: FxHashMap<LocalDefId, Span> = tcx
.maybe_unused_extern_crates(())
.iter()
.filter(|&&(def_id, _)| {
tcx.extern_mod_stmt_cnum(def_id).map_or(true, |cnum| {
!tcx.is_compiler_builtins(cnum)
&& !tcx.is_panic_runtime(cnum)
&& !tcx.has_global_allocator(cnum)
&& !tcx.has_panic_handler(cnum)
})
})
.cloned()
.collect();
// Collect all the extern crates (in a reliable order).
let mut crates_to_lint = vec![];
for id in tcx.hir().items() {
if matches!(tcx.def_kind(id.owner_id), DefKind::ExternCrate) {
let item = tcx.hir().item(id);
if let hir::ItemKind::ExternCrate(orig_name) = item.kind {
crates_to_lint.push(ExternCrateToLint {
def_id: item.owner_id.to_def_id(),
span: item.span,
orig_name,
warn_if_unused: !item.ident.as_str().starts_with('_'),
});
}
}
}
let extern_prelude = &tcx.resolutions(()).extern_prelude;
for extern_crate in &crates_to_lint {
let def_id = extern_crate.def_id.expect_local();
let item = tcx.hir().expect_item(def_id);
// If the crate is fully unused, we suggest removing it altogether.
// We do this in any edition.
if extern_crate.warn_if_unused {
if let Some(&span) = unused_extern_crates.get(&def_id) {
// Removal suggestion span needs to include attributes (Issue #54400)
let id = tcx.hir().local_def_id_to_hir_id(def_id);
let span_with_attrs = tcx
.hir()
.attrs(id)
.iter()
.map(|attr| attr.span)
.fold(span, |acc, attr_span| acc.to(attr_span));
tcx.emit_spanned_lint(lint, id, span, UnusedExternCrate { span: span_with_attrs });
continue;
}
}
// If we are not in Rust 2018 edition, then we don't make any further
// suggestions.
if !tcx.sess.rust_2018() {
continue;
}
// If the extern crate isn't in the extern prelude,
// there is no way it can be written as a `use`.
let orig_name = extern_crate.orig_name.unwrap_or(item.ident.name);
if !extern_prelude.get(&orig_name).map_or(false, |from_item| !from_item) {
continue;
}
// If the extern crate is renamed, then we cannot suggest replacing it with a use as this
// would not insert the new name into the prelude, where other imports in the crate may be
// expecting it.
if extern_crate.orig_name.is_some() {
continue;
}
let id = tcx.hir().local_def_id_to_hir_id(def_id);
// If the extern crate has any attributes, they may have funky
// semantics we can't faithfully represent using `use` (most
// notably `#[macro_use]`). Ignore it.
if !tcx.hir().attrs(id).is_empty() {
continue;
}
let base_replacement = match extern_crate.orig_name {
Some(orig_name) => format!("use {} as {};", orig_name, item.ident.name),
None => format!("use {};", item.ident.name),
};
let vis = tcx.sess.source_map().span_to_snippet(item.vis_span).unwrap_or_default();
let add_vis = |to| if vis.is_empty() { to } else { format!("{} {}", vis, to) };
tcx.emit_spanned_lint(
lint,
id,
extern_crate.span,
ExternCrateNotIdiomatic {
span: extern_crate.span,
msg_code: add_vis("use".to_string()),
suggestion_code: add_vis(base_replacement),
},
);
}
}
struct ExternCrateToLint {
/// `DefId` of the extern crate
def_id: DefId,
/// span from the item
span: Span,
/// if `Some`, then this is renamed (`extern crate orig_name as
/// crate_name`), and -- perhaps surprisingly -- this stores the
/// *original* name (`item.name` will contain the new name)
orig_name: Option<Symbol>,
/// if `false`, the original name started with `_`, so we shouldn't lint
/// about it going unused (but we should still emit idiom lints).
warn_if_unused: bool,
}

22
compiler/rustc_hir_analysis/src/errors.rs
View File

@ -5,7 +5,7 @@ use rustc_errors::{
error_code, Applicability, DiagnosticBuilder, ErrorGuaranteed, Handler, IntoDiagnostic,
MultiSpan,
};
use rustc_macros::{Diagnostic, LintDiagnostic};
use rustc_macros::Diagnostic;
use rustc_middle::ty::Ty;
use rustc_span::{symbol::Ident, Span, Symbol};
@ -247,26 +247,6 @@ pub struct SubstsOnOverriddenImpl {
pub span: Span,
}
#[derive(LintDiagnostic)]
#[diag(hir_analysis_unused_extern_crate)]
pub struct UnusedExternCrate {
#[suggestion(applicability = "machine-applicable", code = "")]
pub span: Span,
}
#[derive(LintDiagnostic)]
#[diag(hir_analysis_extern_crate_not_idiomatic)]
pub struct ExternCrateNotIdiomatic {
#[suggestion(
style = "short",
applicability = "machine-applicable",
code = "{suggestion_code}"
)]
pub span: Span,
pub msg_code: String,
pub suggestion_code: String,
}
#[derive(Diagnostic)]
#[diag(hir_analysis_const_impl_for_non_const_trait)]
pub struct ConstImplForNonConstTrait {

17
compiler/rustc_lint/src/context.rs
View File

@ -893,6 +893,23 @@ pub trait LintContext: Sized {
BuiltinLintDiagnostics::ByteSliceInPackedStructWithDerive => {
db.help("consider implementing the trait by hand, or remove the `packed` attribute");
}
BuiltinLintDiagnostics::UnusedExternCrate { removal_span }=> {
db.span_suggestion(
removal_span,
"remove it",
"",
Applicability::MachineApplicable,
);
}
BuiltinLintDiagnostics::ExternCrateNotIdiomatic { vis_span, ident_span }=> {
let suggestion_span = vis_span.between(ident_span);
db.span_suggestion_verbose(
suggestion_span,
"convert it to a `use`",
if vis_span.is_empty() { "use " } else { " use " },
Applicability::MachineApplicable,
);
}
}
// Rewrap `db`, and pass control to the user.
decorate(db)

7
compiler/rustc_lint_defs/src/lib.rs
View File

@ -522,6 +522,13 @@ pub enum BuiltinLintDiagnostics {
is_formatting_arg: bool,
},
ByteSliceInPackedStructWithDerive,
UnusedExternCrate {
removal_span: Span,
},
ExternCrateNotIdiomatic {
vis_span: Span,
ident_span: Span,
},
}
/// Lints that are buffered up early on in the `Session` before the

138
compiler/rustc_resolve/src/check_unused.rs
View File

@ -29,11 +29,12 @@ use crate::Resolver;
use rustc_ast as ast;
use rustc_ast::visit::{self, Visitor};
use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
use rustc_data_structures::unord::UnordSet;
use rustc_errors::{pluralize, MultiSpan};
use rustc_session::lint::builtin::{MACRO_USE_EXTERN_CRATE, UNUSED_IMPORTS};
use rustc_session::lint::builtin::{MACRO_USE_EXTERN_CRATE, UNUSED_EXTERN_CRATES, UNUSED_IMPORTS};
use rustc_session::lint::BuiltinLintDiagnostics;
use rustc_span::symbol::{Ident, Symbol};
use rustc_span::{Span, DUMMY_SP};
struct UnusedImport<'a> {
@ -53,11 +54,30 @@ struct UnusedImportCheckVisitor<'a, 'b, 'tcx> {
r: &'a mut Resolver<'b, 'tcx>,
/// All the (so far) unused imports, grouped path list
unused_imports: FxIndexMap<ast::NodeId, UnusedImport<'a>>,
extern_crate_items: Vec<ExternCrateToLint>,
base_use_tree: Option<&'a ast::UseTree>,
base_id: ast::NodeId,
item_span: Span,
}
struct ExternCrateToLint {
id: ast::NodeId,
/// Span from the item
span: Span,
/// Span to use to suggest complete removal.
span_with_attributes: Span,
/// Span of the visibility, if any.
vis_span: Span,
/// Whether the item has attrs.
has_attrs: bool,
/// Name used to refer to the crate.
ident: Ident,
/// If `Some`, then this is renamed (`extern crate orig_name as
/// crate_name`), and -- perhaps surprisingly -- this stores the
/// *original* name (`item.name` will contain the new name)
orig_name: Option<Symbol>,
}
impl<'a, 'b, 'tcx> UnusedImportCheckVisitor<'a, 'b, 'tcx> {
// We have information about whether `use` (import) items are actually
// used now. If an import is not used at all, we signal a lint error.
@ -96,18 +116,27 @@ impl<'a, 'b, 'tcx> UnusedImportCheckVisitor<'a, 'b, 'tcx> {
impl<'a, 'b, 'tcx> Visitor<'a> for UnusedImportCheckVisitor<'a, 'b, 'tcx> {
fn visit_item(&mut self, item: &'a ast::Item) {
self.item_span = item.span_with_attributes();
// Ignore is_public import statements because there's no way to be sure
// whether they're used or not. Also ignore imports with a dummy span
// because this means that they were generated in some fashion by the
// compiler and we don't need to consider them.
if let ast::ItemKind::Use(..) = item.kind {
if item.vis.kind.is_pub() || item.span.is_dummy() {
return;
match item.kind {
// Ignore is_public import statements because there's no way to be sure
// whether they're used or not. Also ignore imports with a dummy span
// because this means that they were generated in some fashion by the
// compiler and we don't need to consider them.
ast::ItemKind::Use(..) if item.vis.kind.is_pub() || item.span.is_dummy() => return,
ast::ItemKind::ExternCrate(orig_name) => {
self.extern_crate_items.push(ExternCrateToLint {
id: item.id,
span: item.span,
vis_span: item.vis.span,
span_with_attributes: item.span_with_attributes(),
has_attrs: !item.attrs.is_empty(),
ident: item.ident,
orig_name,
});
}
_ => {}
}
self.item_span = item.span_with_attributes();
visit::walk_item(self, item);
}
@ -224,6 +253,9 @@ fn calc_unused_spans(
impl Resolver<'_, '_> {
pub(crate) fn check_unused(&mut self, krate: &ast::Crate) {
let tcx = self.tcx;
let mut maybe_unused_extern_crates = FxHashMap::default();
for import in self.potentially_unused_imports.iter() {
match import.kind {
_ if import.used.get()
@ -247,6 +279,14 @@ impl Resolver<'_, '_> {
ImportKind::ExternCrate { id, .. } => {
let def_id = self.local_def_id(id);
self.maybe_unused_extern_crates.push((def_id, import.span));
if self.extern_crate_map.get(&def_id).map_or(true, |&cnum| {
!tcx.is_compiler_builtins(cnum)
&& !tcx.is_panic_runtime(cnum)
&& !tcx.has_global_allocator(cnum)
&& !tcx.has_panic_handler(cnum)
}) {
maybe_unused_extern_crates.insert(id, import.span);
}
}
ImportKind::MacroUse => {
let msg = "unused `#[macro_use]` import";
@ -259,6 +299,7 @@ impl Resolver<'_, '_> {
let mut visitor = UnusedImportCheckVisitor {
r: self,
unused_imports: Default::default(),
extern_crate_items: Default::default(),
base_use_tree: None,
base_id: ast::DUMMY_NODE_ID,
item_span: DUMMY_SP,
@ -290,7 +331,7 @@ impl Resolver<'_, '_> {
let ms = MultiSpan::from_spans(spans.clone());
let mut span_snippets = spans
.iter()
.filter_map(|s| match visitor.r.tcx.sess.source_map().span_to_snippet(*s) {
.filter_map(|s| match tcx.sess.source_map().span_to_snippet(*s) {
Ok(s) => Some(format!("`{}`", s)),
_ => None,
})
@ -317,7 +358,7 @@ impl Resolver<'_, '_> {
// If we are in the `--test` mode, suppress a help that adds the `#[cfg(test)]`
// attribute; however, if not, suggest adding the attribute. There is no way to
// retrieve attributes here because we do not have a `TyCtxt` yet.
let test_module_span = if visitor.r.tcx.sess.opts.test {
let test_module_span = if tcx.sess.opts.test {
None
} else {
let parent_module = visitor.r.get_nearest_non_block_module(
@ -346,5 +387,76 @@ impl Resolver<'_, '_> {
BuiltinLintDiagnostics::UnusedImports(fix_msg.into(), fixes, test_module_span),
);
}
for extern_crate in visitor.extern_crate_items {
let warn_if_unused = !extern_crate.ident.name.as_str().starts_with('_');
// If the crate is fully unused, we suggest removing it altogether.
// We do this in any edition.
if warn_if_unused {
if let Some(&span) = maybe_unused_extern_crates.get(&extern_crate.id) {
visitor.r.lint_buffer.buffer_lint_with_diagnostic(
UNUSED_EXTERN_CRATES,
extern_crate.id,
span,
"unused extern crate",
BuiltinLintDiagnostics::UnusedExternCrate {
removal_span: extern_crate.span_with_attributes,
},
);
continue;
}
}
// If we are not in Rust 2018 edition, then we don't make any further
// suggestions.
if !tcx.sess.rust_2018() {
continue;
}
// If the extern crate has any attributes, they may have funky
// semantics we can't faithfully represent using `use` (most
// notably `#[macro_use]`). Ignore it.
if extern_crate.has_attrs {
continue;
}
// If the extern crate is renamed, then we cannot suggest replacing it with a use as this
// would not insert the new name into the prelude, where other imports in the crate may be
// expecting it.
if extern_crate.orig_name.is_some() {
continue;
}
// If the extern crate isn't in the extern prelude,
// there is no way it can be written as a `use`.
let usage_name =
extern_crate.orig_name.map_or(extern_crate.ident, Ident::with_dummy_span);
if !visitor
.r
.extern_prelude
.get(&usage_name)
.map_or(false, |entry| !entry.introduced_by_item)
{
continue;
}
let vis_span = extern_crate
.vis_span
.find_ancestor_inside(extern_crate.span)
.unwrap_or(extern_crate.vis_span);
let ident_span = extern_crate
.ident
.span
.find_ancestor_inside(extern_crate.span)
.unwrap_or(extern_crate.ident.span);
visitor.r.lint_buffer.buffer_lint_with_diagnostic(
UNUSED_EXTERN_CRATES,
extern_crate.id,
extern_crate.span,
"`extern crate` is not idiomatic in the new edition",
BuiltinLintDiagnostics::ExternCrateNotIdiomatic { vis_span, ident_span },
);
}
}
}

10
tests/ui/rust-2018/remove-extern-crate.fixed
View File

@ -23,6 +23,7 @@ extern crate alloc;
fn main() {
another_name::mem::drop(3);
another::foo();
with_visibility::foo();
remove_extern_crate::foo!();
bar!();
alloc::vec![5];
@ -37,3 +38,12 @@ mod another {
remove_extern_crate::foo!();
}
}
mod with_visibility {
pub use core; //~ WARNING `extern crate` is not idiomatic
pub fn foo() {
core::mem::drop(4);
remove_extern_crate::foo!();
}
}

10
tests/ui/rust-2018/remove-extern-crate.rs
View File

@ -23,6 +23,7 @@ extern crate alloc;
fn main() {
another_name::mem::drop(3);
another::foo();
with_visibility::foo();
remove_extern_crate::foo!();
bar!();
alloc::vec![5];
@ -37,3 +38,12 @@ mod another {
remove_extern_crate::foo!();
}
}
mod with_visibility {
pub extern crate core; //~ WARNING `extern crate` is not idiomatic
pub fn foo() {
core::mem::drop(4);
remove_extern_crate::foo!();
}
}

22
tests/ui/rust-2018/remove-extern-crate.stderr
View File

@ -12,10 +12,26 @@ LL | #![warn(rust_2018_idioms)]
= note: `#[warn(unused_extern_crates)]` implied by `#[warn(rust_2018_idioms)]`
warning: `extern crate` is not idiomatic in the new edition
--> $DIR/remove-extern-crate.rs:32:5
--> $DIR/remove-extern-crate.rs:33:5
|
LL | extern crate core;
| ^^^^^^^^^^^^^^^^^^ help: convert it to a `use`
| ^^^^^^^^^^^^^^^^^^
|
help: convert it to a `use`
|
LL | use core;
| ~~~
warning: 2 warnings emitted
warning: `extern crate` is not idiomatic in the new edition
--> $DIR/remove-extern-crate.rs:43:5
|
LL | pub extern crate core;
| ^^^^^^^^^^^^^^^^^^^^^^
|
help: convert it to a `use`
|
LL | pub use core;
| ~~~
warning: 3 warnings emitted