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};
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)
37 #[clippy::version = "pre 1.29.0"]
40 "use items that import all variants of an enum"
43 declare_clippy_lint! {
45 /// Checks for wildcard imports `use _::*`.
47 /// ### Why is this bad?
48 /// wildcard imports can pollute the namespace. This is especially bad if
49 /// you try to import something through a wildcard, that already has been imported by name from
50 /// a different source:
53 /// use crate1::foo; // Imports a function named foo
54 /// use crate2::*; // Has a function named foo
56 /// foo(); // Calls crate1::foo
59 /// This can lead to confusing error messages at best and to unexpected behavior at worst.
62 /// Wildcard imports are allowed from modules named `prelude`. Many crates (including the standard library)
63 /// provide modules named "prelude" specifically designed for wildcard import.
65 /// `use super::*` is allowed in test modules. This is defined as any module with "test" in the name.
67 /// These exceptions can be disabled using the `warn-on-all-wildcard-imports` configuration flag.
69 /// ### Known problems
70 /// If macros are imported through the wildcard, this macro is not included
71 /// by the suggestion and has to be added by hand.
73 /// Applying the suggestion when explicit imports of the things imported with a glob import
74 /// exist, may result in `unused_imports` warnings.
90 #[clippy::version = "1.43.0"]
93 "lint `use _::*` statements"
97 pub struct WildcardImports {
99 test_modules_deep: u32,
102 impl WildcardImports {
103 pub fn new(warn_on_all: bool) -> Self {
106 test_modules_deep: 0,
111 impl_lint_pass!(WildcardImports => [ENUM_GLOB_USE, WILDCARD_IMPORTS]);
113 impl LateLintPass<'_> for WildcardImports {
114 fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
115 if is_test_module_or_function(cx.tcx, item) {
116 self.test_modules_deep = self.test_modules_deep.saturating_add(1);
118 if item.vis.node.is_pub() || item.vis.node.is_pub_restricted() {
122 if let ItemKind::Use(use_path, UseKind::Glob) = &item.kind;
123 if self.warn_on_all || !self.check_exceptions(item, use_path.segments);
124 let used_imports = cx.tcx.names_imported_by_glob_use(item.def_id);
125 if !used_imports.is_empty(); // Already handled by `unused_imports`
127 let mut applicability = Applicability::MachineApplicable;
128 let import_source_snippet = snippet_with_applicability(cx, use_path.span, "..", &mut applicability);
129 let (span, braced_glob) = if import_source_snippet.is_empty() {
130 // This is a `_::{_, *}` import
131 // In this case `use_path.span` is empty and ends directly in front of the `*`,
132 // so we need to extend it by one byte.
134 use_path.span.with_hi(use_path.span.hi() + BytePos(1)),
138 // In this case, the `use_path.span` ends right before the `::*`, so we need to
139 // extend it up to the `*`. Since it is hard to find the `*` in weird
140 // formattings like `use _ :: *;`, we extend it up to, but not including the
141 // `;`. In nested imports, like `use _::{inner::*, _}` there is no `;` and we
142 // can just use the end of the item span
143 let mut span = use_path.span.with_hi(item.span.hi());
144 if snippet(cx, span, "").ends_with(';') {
145 span = use_path.span.with_hi(item.span.hi() - BytePos(1));
152 let imports_string = if used_imports.len() == 1 {
153 used_imports.iter().next().unwrap().to_string()
155 let mut imports = used_imports
157 .map(ToString::to_string)
158 .collect::<Vec<_>>();
163 format!("{{{}}}", imports.join(", "))
167 let sugg = if braced_glob {
170 format!("{}::{}", import_source_snippet, imports_string)
173 let (lint, message) = if let Res::Def(DefKind::Enum, _) = use_path.res {
174 (ENUM_GLOB_USE, "usage of wildcard import for enum variants")
176 (WILDCARD_IMPORTS, "usage of wildcard import")
192 fn check_item_post(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
193 if is_test_module_or_function(cx.tcx, item) {
194 self.test_modules_deep = self.test_modules_deep.saturating_sub(1);
199 impl WildcardImports {
200 fn check_exceptions(&self, item: &Item<'_>, segments: &[PathSegment<'_>]) -> bool {
201 item.span.from_expansion()
202 || is_prelude_import(segments)
203 || (is_super_only_import(segments) && self.test_modules_deep > 0)
207 // Allow "...prelude::..::*" imports.
208 // Many crates have a prelude, and it is imported as a glob by design.
209 fn is_prelude_import(segments: &[PathSegment<'_>]) -> bool {
210 segments.iter().any(|ps| ps.ident.name == sym::prelude)
213 // Allow "super::*" imports in tests.
214 fn is_super_only_import(segments: &[PathSegment<'_>]) -> bool {
215 segments.len() == 1 && segments[0].ident.name == kw::Super