1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::is_test_module_or_function;
3 use clippy_utils::source::{snippet, snippet_with_applicability};
4 use if_chain::if_chain;
5 use rustc_errors::Applicability;
8 Item, ItemKind, PathSegment, UseKind,
10 use rustc_lint::{LateContext, LateLintPass};
12 use rustc_session::{declare_tool_lint, impl_lint_pass};
13 use rustc_span::symbol::kw;
14 use rustc_span::{sym, BytePos};
16 declare_clippy_lint! {
18 /// Checks for `use Enum::*`.
20 /// ### Why is this bad?
21 /// It is usually better style to use the prefixed name of
22 /// an enumeration variant, rather than importing variants.
24 /// ### Known problems
25 /// Old-style enumerations that prefix the variants are
30 /// use std::cmp::Ordering::*;
32 /// # fn foo(_: std::cmp::Ordering) {}
38 /// use std::cmp::Ordering;
40 /// # fn foo(_: Ordering) {}
41 /// foo(Ordering::Less)
43 #[clippy::version = "pre 1.29.0"]
46 "use items that import all variants of an enum"
49 declare_clippy_lint! {
51 /// Checks for wildcard imports `use _::*`.
53 /// ### Why is this bad?
54 /// wildcard imports can pollute the namespace. This is especially bad if
55 /// you try to import something through a wildcard, that already has been imported by name from
56 /// a different source:
59 /// use crate1::foo; // Imports a function named foo
60 /// use crate2::*; // Has a function named foo
62 /// foo(); // Calls crate1::foo
65 /// This can lead to confusing error messages at best and to unexpected behavior at worst.
68 /// Wildcard imports are allowed from modules named `prelude`. Many crates (including the standard library)
69 /// provide modules named "prelude" specifically designed for wildcard import.
71 /// `use super::*` is allowed in test modules. This is defined as any module with "test" in the name.
73 /// These exceptions can be disabled using the `warn-on-all-wildcard-imports` configuration flag.
75 /// ### Known problems
76 /// If macros are imported through the wildcard, this macro is not included
77 /// by the suggestion and has to be added by hand.
79 /// Applying the suggestion when explicit imports of the things imported with a glob import
80 /// exist, may result in `unused_imports` warnings.
95 #[clippy::version = "1.43.0"]
98 "lint `use _::*` statements"
102 pub struct WildcardImports {
104 test_modules_deep: u32,
107 impl WildcardImports {
108 pub fn new(warn_on_all: bool) -> Self {
111 test_modules_deep: 0,
116 impl_lint_pass!(WildcardImports => [ENUM_GLOB_USE, WILDCARD_IMPORTS]);
118 impl LateLintPass<'_> for WildcardImports {
119 fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
120 if is_test_module_or_function(cx.tcx, item) {
121 self.test_modules_deep = self.test_modules_deep.saturating_add(1);
123 let module = cx.tcx.parent_module_from_def_id(item.def_id);
124 if cx.tcx.visibility(item.def_id) != ty::Visibility::Restricted(module.to_def_id()) {
128 if let ItemKind::Use(use_path, UseKind::Glob) = &item.kind;
129 if self.warn_on_all || !self.check_exceptions(item, use_path.segments);
130 let used_imports = cx.tcx.names_imported_by_glob_use(item.def_id);
131 if !used_imports.is_empty(); // Already handled by `unused_imports`
133 let mut applicability = Applicability::MachineApplicable;
134 let import_source_snippet = snippet_with_applicability(cx, use_path.span, "..", &mut applicability);
135 let (span, braced_glob) = if import_source_snippet.is_empty() {
136 // This is a `_::{_, *}` import
137 // In this case `use_path.span` is empty and ends directly in front of the `*`,
138 // so we need to extend it by one byte.
140 use_path.span.with_hi(use_path.span.hi() + BytePos(1)),
144 // In this case, the `use_path.span` ends right before the `::*`, so we need to
145 // extend it up to the `*`. Since it is hard to find the `*` in weird
146 // formattings like `use _ :: *;`, we extend it up to, but not including the
147 // `;`. In nested imports, like `use _::{inner::*, _}` there is no `;` and we
148 // can just use the end of the item span
149 let mut span = use_path.span.with_hi(item.span.hi());
150 if snippet(cx, span, "").ends_with(';') {
151 span = use_path.span.with_hi(item.span.hi() - BytePos(1));
158 let imports_string = if used_imports.len() == 1 {
159 used_imports.iter().next().unwrap().to_string()
161 let mut imports = used_imports
163 .map(ToString::to_string)
164 .collect::<Vec<_>>();
169 format!("{{{}}}", imports.join(", "))
173 let sugg = if braced_glob {
176 format!("{}::{}", import_source_snippet, imports_string)
179 let (lint, message) = if let Res::Def(DefKind::Enum, _) = use_path.res {
180 (ENUM_GLOB_USE, "usage of wildcard import for enum variants")
182 (WILDCARD_IMPORTS, "usage of wildcard import")
198 fn check_item_post(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
199 if is_test_module_or_function(cx.tcx, item) {
200 self.test_modules_deep = self.test_modules_deep.saturating_sub(1);
205 impl WildcardImports {
206 fn check_exceptions(&self, item: &Item<'_>, segments: &[PathSegment<'_>]) -> bool {
207 item.span.from_expansion()
208 || is_prelude_import(segments)
209 || (is_super_only_import(segments) && self.test_modules_deep > 0)
213 // Allow "...prelude::..::*" imports.
214 // Many crates have a prelude, and it is imported as a glob by design.
215 fn is_prelude_import(segments: &[PathSegment<'_>]) -> bool {
216 segments.iter().any(|ps| ps.ident.name == sym::prelude)
219 // Allow "super::*" imports in tests.
220 fn is_super_only_import(segments: &[PathSegment<'_>]) -> bool {
221 segments.len() == 1 && segments[0].ident.name == kw::Super