1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::source::{snippet, snippet_with_applicability};
3 use clippy_utils::{in_macro, is_test_module_or_function};
4 use if_chain::if_chain;
5 use rustc_errors::Applicability;
8 Item, ItemKind, PathSegment, UseKind,
10 use rustc_lint::{LateContext, LateLintPass};
11 use rustc_session::{declare_tool_lint, impl_lint_pass};
12 use rustc_span::symbol::kw;
13 use rustc_span::{sym, BytePos};
15 declare_clippy_lint! {
17 /// Checks for `use Enum::*`.
19 /// ### Why is this bad?
20 /// It is usually better style to use the prefixed name of
21 /// an enumeration variant, rather than importing variants.
23 /// ### Known problems
24 /// Old-style enumerations that prefix the variants are
30 /// use std::cmp::Ordering::*;
34 /// use std::cmp::Ordering;
35 /// foo(Ordering::Less)
39 "use items that import all variants of an enum"
42 declare_clippy_lint! {
44 /// Checks for wildcard imports `use _::*`.
46 /// ### Why is this bad?
47 /// wildcard imports can pollute the namespace. This is especially bad if
48 /// you try to import something through a wildcard, that already has been imported by name from
49 /// a different source:
52 /// use crate1::foo; // Imports a function named foo
53 /// use crate2::*; // Has a function named foo
55 /// foo(); // Calls crate1::foo
58 /// This can lead to confusing error messages at best and to unexpected behavior at worst.
61 /// Wildcard imports are allowed from modules named `prelude`. Many crates (including the standard library)
62 /// provide modules named "prelude" specifically designed for wildcard import.
64 /// `use super::*` is allowed in test modules. This is defined as any module with "test" in the name.
66 /// These exceptions can be disabled using the `warn-on-all-wildcard-imports` configuration flag.
68 /// ### Known problems
69 /// If macros are imported through the wildcard, this macro is not included
70 /// by the suggestion and has to be added by hand.
72 /// Applying the suggestion when explicit imports of the things imported with a glob import
73 /// exist, may result in `unused_imports` warnings.
91 "lint `use _::*` statements"
95 pub struct WildcardImports {
97 test_modules_deep: u32,
100 impl WildcardImports {
101 pub fn new(warn_on_all: bool) -> Self {
104 test_modules_deep: 0,
109 impl_lint_pass!(WildcardImports => [ENUM_GLOB_USE, WILDCARD_IMPORTS]);
111 impl LateLintPass<'_> for WildcardImports {
112 fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
113 if is_test_module_or_function(cx.tcx, item) {
114 self.test_modules_deep = self.test_modules_deep.saturating_add(1);
116 if item.vis.node.is_pub() || item.vis.node.is_pub_restricted() {
120 if let ItemKind::Use(use_path, UseKind::Glob) = &item.kind;
121 if self.warn_on_all || !self.check_exceptions(item, use_path.segments);
122 let used_imports = cx.tcx.names_imported_by_glob_use(item.def_id);
123 if !used_imports.is_empty(); // Already handled by `unused_imports`
125 let mut applicability = Applicability::MachineApplicable;
126 let import_source_snippet = snippet_with_applicability(cx, use_path.span, "..", &mut applicability);
127 let (span, braced_glob) = if import_source_snippet.is_empty() {
128 // This is a `_::{_, *}` import
129 // In this case `use_path.span` is empty and ends directly in front of the `*`,
130 // so we need to extend it by one byte.
132 use_path.span.with_hi(use_path.span.hi() + BytePos(1)),
136 // In this case, the `use_path.span` ends right before the `::*`, so we need to
137 // extend it up to the `*`. Since it is hard to find the `*` in weird
138 // formattings like `use _ :: *;`, we extend it up to, but not including the
139 // `;`. In nested imports, like `use _::{inner::*, _}` there is no `;` and we
140 // can just use the end of the item span
141 let mut span = use_path.span.with_hi(item.span.hi());
142 if snippet(cx, span, "").ends_with(';') {
143 span = use_path.span.with_hi(item.span.hi() - BytePos(1));
150 let imports_string = if used_imports.len() == 1 {
151 used_imports.iter().next().unwrap().to_string()
153 let mut imports = used_imports
155 .map(ToString::to_string)
156 .collect::<Vec<_>>();
161 format!("{{{}}}", imports.join(", "))
165 let sugg = if braced_glob {
168 format!("{}::{}", import_source_snippet, imports_string)
171 let (lint, message) = if let Res::Def(DefKind::Enum, _) = use_path.res {
172 (ENUM_GLOB_USE, "usage of wildcard import for enum variants")
174 (WILDCARD_IMPORTS, "usage of wildcard import")
190 fn check_item_post(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
191 if is_test_module_or_function(cx.tcx, item) {
192 self.test_modules_deep = self.test_modules_deep.saturating_sub(1);
197 impl WildcardImports {
198 fn check_exceptions(&self, item: &Item<'_>, segments: &[PathSegment<'_>]) -> bool {
200 || is_prelude_import(segments)
201 || (is_super_only_import(segments) && self.test_modules_deep > 0)
205 // Allow "...prelude::..::*" imports.
206 // Many crates have a prelude, and it is imported as a glob by design.
207 fn is_prelude_import(segments: &[PathSegment<'_>]) -> bool {
208 segments.iter().any(|ps| ps.ident.name == sym::prelude)
211 // Allow "super::*" imports in tests.
212 fn is_super_only_import(segments: &[PathSegment<'_>]) -> bool {
213 segments.len() == 1 && segments[0].ident.name == kw::Super