Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 350 insertions, 0 deletions

diff --git a/compiler/rustc_resolve/src/check_unused.rs b/compiler/rustc_resolve/src/check_unused.rs
new file mode 100644
index 000000000..f2f6f1d89
--- /dev/null
+++ b/compiler/rustc_resolve/src/check_unused.rs
@@ -0,0 +1,350 @@
+//
+// Unused import checking
+//
+// Although this is mostly a lint pass, it lives in here because it depends on
+// resolve data structures and because it finalises the privacy information for
+// `use` items.
+//
+// Unused trait imports can't be checked until the method resolution. We save
+// candidates here, and do the actual check in librustc_typeck/check_unused.rs.
+//
+// Checking for unused imports is split into three steps:
+//
+//  - `UnusedImportCheckVisitor` walks the AST to find all the unused imports
+//    inside of `UseTree`s, recording their `NodeId`s and grouping them by
+//    the parent `use` item
+//
+//  - `calc_unused_spans` then walks over all the `use` items marked in the
+//    previous step to collect the spans associated with the `NodeId`s and to
+//    calculate the spans that can be removed by rustfix; This is done in a
+//    separate step to be able to collapse the adjacent spans that rustfix
+//    will remove
+//
+//  - `check_crate` finally emits the diagnostics based on the data generated
+//    in the last step
+
+use crate::imports::ImportKind;
+use crate::module_to_string;
+use crate::Resolver;
+
+use rustc_ast as ast;
+use rustc_ast::node_id::NodeMap;
+use rustc_ast::visit::{self, Visitor};
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::{pluralize, MultiSpan};
+use rustc_session::lint::builtin::{MACRO_USE_EXTERN_CRATE, UNUSED_IMPORTS};
+use rustc_session::lint::BuiltinLintDiagnostics;
+use rustc_span::{Span, DUMMY_SP};
+
+struct UnusedImport<'a> {
+    use_tree: &'a ast::UseTree,
+    use_tree_id: ast::NodeId,
+    item_span: Span,
+    unused: FxHashSet<ast::NodeId>,
+}
+
+impl<'a> UnusedImport<'a> {
+    fn add(&mut self, id: ast::NodeId) {
+        self.unused.insert(id);
+    }
+}
+
+struct UnusedImportCheckVisitor<'a, 'b> {
+    r: &'a mut Resolver<'b>,
+    /// All the (so far) unused imports, grouped path list
+    unused_imports: NodeMap<UnusedImport<'a>>,
+    base_use_tree: Option<&'a ast::UseTree>,
+    base_id: ast::NodeId,
+    item_span: Span,
+}
+
+impl<'a, 'b> UnusedImportCheckVisitor<'a, 'b> {
+    // 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.
+    fn check_import(&mut self, id: ast::NodeId) {
+        let used = self.r.used_imports.contains(&id);
+        let def_id = self.r.local_def_id(id);
+        if !used {
+            if self.r.maybe_unused_trait_imports.contains(&def_id) {
+                // Check later.
+                return;
+            }
+            self.unused_import(self.base_id).add(id);
+        } else {
+            // This trait import is definitely used, in a way other than
+            // method resolution.
+            self.r.maybe_unused_trait_imports.remove(&def_id);
+            if let Some(i) = self.unused_imports.get_mut(&self.base_id) {
+                i.unused.remove(&id);
+            }
+        }
+    }
+
+    fn unused_import(&mut self, id: ast::NodeId) -> &mut UnusedImport<'a> {
+        let use_tree_id = self.base_id;
+        let use_tree = self.base_use_tree.unwrap();
+        let item_span = self.item_span;
+
+        self.unused_imports.entry(id).or_insert_with(|| UnusedImport {
+            use_tree,
+            use_tree_id,
+            item_span,
+            unused: FxHashSet::default(),
+        })
+    }
+}
+
+impl<'a, 'b> Visitor<'a> for UnusedImportCheckVisitor<'a, 'b> {
+    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;
+            }
+        }
+
+        visit::walk_item(self, item);
+    }
+
+    fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: ast::NodeId, nested: bool) {
+        // Use the base UseTree's NodeId as the item id
+        // This allows the grouping of all the lints in the same item
+        if !nested {
+            self.base_id = id;
+            self.base_use_tree = Some(use_tree);
+        }
+
+        if let ast::UseTreeKind::Nested(ref items) = use_tree.kind {
+            if items.is_empty() {
+                self.unused_import(self.base_id).add(id);
+            }
+        } else {
+            self.check_import(id);
+        }
+
+        visit::walk_use_tree(self, use_tree, id);
+    }
+}
+
+enum UnusedSpanResult {
+    Used,
+    FlatUnused(Span, Span),
+    NestedFullUnused(Vec<Span>, Span),
+    NestedPartialUnused(Vec<Span>, Vec<Span>),
+}
+
+fn calc_unused_spans(
+    unused_import: &UnusedImport<'_>,
+    use_tree: &ast::UseTree,
+    use_tree_id: ast::NodeId,
+) -> UnusedSpanResult {
+    // The full span is the whole item's span if this current tree is not nested inside another
+    // This tells rustfix to remove the whole item if all the imports are unused
+    let full_span = if unused_import.use_tree.span == use_tree.span {
+        unused_import.item_span
+    } else {
+        use_tree.span
+    };
+    match use_tree.kind {
+        ast::UseTreeKind::Simple(..) | ast::UseTreeKind::Glob => {
+            if unused_import.unused.contains(&use_tree_id) {
+                UnusedSpanResult::FlatUnused(use_tree.span, full_span)
+            } else {
+                UnusedSpanResult::Used
+            }
+        }
+        ast::UseTreeKind::Nested(ref nested) => {
+            if nested.is_empty() {
+                return UnusedSpanResult::FlatUnused(use_tree.span, full_span);
+            }
+
+            let mut unused_spans = Vec::new();
+            let mut to_remove = Vec::new();
+            let mut all_nested_unused = true;
+            let mut previous_unused = false;
+            for (pos, (use_tree, use_tree_id)) in nested.iter().enumerate() {
+                let remove = match calc_unused_spans(unused_import, use_tree, *use_tree_id) {
+                    UnusedSpanResult::Used => {
+                        all_nested_unused = false;
+                        None
+                    }
+                    UnusedSpanResult::FlatUnused(span, remove) => {
+                        unused_spans.push(span);
+                        Some(remove)
+                    }
+                    UnusedSpanResult::NestedFullUnused(mut spans, remove) => {
+                        unused_spans.append(&mut spans);
+                        Some(remove)
+                    }
+                    UnusedSpanResult::NestedPartialUnused(mut spans, mut to_remove_extra) => {
+                        all_nested_unused = false;
+                        unused_spans.append(&mut spans);
+                        to_remove.append(&mut to_remove_extra);
+                        None
+                    }
+                };
+                if let Some(remove) = remove {
+                    let remove_span = if nested.len() == 1 {
+                        remove
+                    } else if pos == nested.len() - 1 || !all_nested_unused {
+                        // Delete everything from the end of the last import, to delete the
+                        // previous comma
+                        nested[pos - 1].0.span.shrink_to_hi().to(use_tree.span)
+                    } else {
+                        // Delete everything until the next import, to delete the trailing commas
+                        use_tree.span.to(nested[pos + 1].0.span.shrink_to_lo())
+                    };
+
+                    // Try to collapse adjacent spans into a single one. This prevents all cases of
+                    // overlapping removals, which are not supported by rustfix
+                    if previous_unused && !to_remove.is_empty() {
+                        let previous = to_remove.pop().unwrap();
+                        to_remove.push(previous.to(remove_span));
+                    } else {
+                        to_remove.push(remove_span);
+                    }
+                }
+                previous_unused = remove.is_some();
+            }
+            if unused_spans.is_empty() {
+                UnusedSpanResult::Used
+            } else if all_nested_unused {
+                UnusedSpanResult::NestedFullUnused(unused_spans, full_span)
+            } else {
+                UnusedSpanResult::NestedPartialUnused(unused_spans, to_remove)
+            }
+        }
+    }
+}
+
+impl Resolver<'_> {
+    pub(crate) fn check_unused(&mut self, krate: &ast::Crate) {
+        for import in self.potentially_unused_imports.iter() {
+            match import.kind {
+                _ if import.used.get()
+                    || import.vis.get().is_public()
+                    || import.span.is_dummy() =>
+                {
+                    if let ImportKind::MacroUse = import.kind {
+                        if !import.span.is_dummy() {
+                            self.lint_buffer.buffer_lint(
+                                MACRO_USE_EXTERN_CRATE,
+                                import.id,
+                                import.span,
+                                "deprecated `#[macro_use]` attribute used to \
+                                import macros should be replaced at use sites \
+                                with a `use` item to import the macro \
+                                instead",
+                            );
+                        }
+                    }
+                }
+                ImportKind::ExternCrate { .. } => {
+                    let def_id = self.local_def_id(import.id);
+                    self.maybe_unused_extern_crates.push((def_id, import.span));
+                }
+                ImportKind::MacroUse => {
+                    let msg = "unused `#[macro_use]` import";
+                    self.lint_buffer.buffer_lint(UNUSED_IMPORTS, import.id, import.span, msg);
+                }
+                _ => {}
+            }
+        }
+
+        let mut visitor = UnusedImportCheckVisitor {
+            r: self,
+            unused_imports: Default::default(),
+            base_use_tree: None,
+            base_id: ast::DUMMY_NODE_ID,
+            item_span: DUMMY_SP,
+        };
+        visit::walk_crate(&mut visitor, krate);
+
+        for unused in visitor.unused_imports.values() {
+            let mut fixes = Vec::new();
+            let mut spans = match calc_unused_spans(unused, unused.use_tree, unused.use_tree_id) {
+                UnusedSpanResult::Used => continue,
+                UnusedSpanResult::FlatUnused(span, remove) => {
+                    fixes.push((remove, String::new()));
+                    vec![span]
+                }
+                UnusedSpanResult::NestedFullUnused(spans, remove) => {
+                    fixes.push((remove, String::new()));
+                    spans
+                }
+                UnusedSpanResult::NestedPartialUnused(spans, remove) => {
+                    for fix in &remove {
+                        fixes.push((*fix, String::new()));
+                    }
+                    spans
+                }
+            };
+
+            let len = spans.len();
+            spans.sort();
+            let ms = MultiSpan::from_spans(spans.clone());
+            let mut span_snippets = spans
+                .iter()
+                .filter_map(|s| match visitor.r.session.source_map().span_to_snippet(*s) {
+                    Ok(s) => Some(format!("`{}`", s)),
+                    _ => None,
+                })
+                .collect::<Vec<String>>();
+            span_snippets.sort();
+            let msg = format!(
+                "unused import{}{}",
+                pluralize!(len),
+                if !span_snippets.is_empty() {
+                    format!(": {}", span_snippets.join(", "))
+                } else {
+                    String::new()
+                }
+            );
+
+            let fix_msg = if fixes.len() == 1 && fixes[0].0 == unused.item_span {
+                "remove the whole `use` item"
+            } else if spans.len() > 1 {
+                "remove the unused imports"
+            } else {
+                "remove the unused import"
+            };
+
+            // 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.session.opts.test {
+                None
+            } else {
+                let parent_module = visitor.r.get_nearest_non_block_module(
+                    visitor.r.local_def_id(unused.use_tree_id).to_def_id(),
+                );
+                match module_to_string(parent_module) {
+                    Some(module)
+                        if module == "test"
+                            || module == "tests"
+                            || module.starts_with("test_")
+                            || module.starts_with("tests_")
+                            || module.ends_with("_test")
+                            || module.ends_with("_tests") =>
+                    {
+                        Some(parent_module.span)
+                    }
+                    _ => None,
+                }
+            };
+
+            visitor.r.lint_buffer.buffer_lint_with_diagnostic(
+                UNUSED_IMPORTS,
+                unused.use_tree_id,
+                ms,
+                &msg,
+                BuiltinLintDiagnostics::UnusedImports(fix_msg.into(), fixes, test_module_span),
+            );
+        }
+    }
+}