1 use crate::utils::{in_macro, snippet, snippet_with_applicability, span_lint_and_sugg};
2 use if_chain::if_chain;
3 use rustc_errors::Applicability;
6 Item, ItemKind, PathSegment, UseKind,
8 use rustc_lint::{LateContext, LateLintPass};
9 use rustc_session::{declare_tool_lint, impl_lint_pass};
10 use rustc_span::BytePos;
12 declare_clippy_lint! {
13 /// **What it does:** Checks for `use Enum::*`.
15 /// **Why is this bad?** It is usually better style to use the prefixed name of
16 /// an enumeration variant, rather than importing variants.
18 /// **Known problems:** Old-style enumerations that prefix the variants are
23 /// use std::cmp::Ordering::*;
27 "use items that import all variants of an enum"
30 declare_clippy_lint! {
31 /// **What it does:** Checks for wildcard imports `use _::*`.
33 /// **Why is this bad?** wildcard imports can polute the namespace. This is especially bad if
34 /// you try to import something through a wildcard, that already has been imported by name from
35 /// a different source:
38 /// use crate1::foo; // Imports a function named foo
39 /// use crate2::*; // Has a function named foo
41 /// foo(); // Calls crate1::foo
44 /// This can lead to confusing error messages at best and to unexpected behavior at worst.
48 /// Wildcard imports are allowed from modules named `prelude`. Many crates (including the standard library)
49 /// provide modules named "prelude" specifically designed for wildcard import.
51 /// `use super::*` is allowed in test modules. This is defined as any module with "test" in the name.
53 /// These exceptions can be disabled using the `warn-on-all-wildcard-imports` configuration flag.
55 /// **Known problems:** If macros are imported through the wildcard, this macro is not included
56 /// by the suggestion and has to be added by hand.
58 /// Applying the suggestion when explicit imports of the things imported with a glob import
59 /// exist, may result in `unused_imports` warnings.
78 "lint `use _::*` statements"
82 pub struct WildcardImports {
84 test_modules_deep: u32,
87 impl WildcardImports {
88 pub fn new(warn_on_all: bool) -> Self {
96 impl_lint_pass!(WildcardImports => [ENUM_GLOB_USE, WILDCARD_IMPORTS]);
98 impl LateLintPass<'_, '_> for WildcardImports {
99 fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &Item<'_>) {
100 if is_test_module_or_function(item) {
101 self.test_modules_deep = self.test_modules_deep.saturating_add(1);
103 if item.vis.node.is_pub() || item.vis.node.is_pub_restricted() {
107 if let ItemKind::Use(use_path, UseKind::Glob) = &item.kind;
108 if self.warn_on_all || !self.check_exceptions(item, use_path.segments);
109 let used_imports = cx.tcx.names_imported_by_glob_use(item.hir_id.owner);
110 if !used_imports.is_empty(); // Already handled by `unused_imports`
112 let mut applicability = Applicability::MachineApplicable;
113 let import_source_snippet = snippet_with_applicability(cx, use_path.span, "..", &mut applicability);
114 let (span, braced_glob) = if import_source_snippet.is_empty() {
115 // This is a `_::{_, *}` import
116 // In this case `use_path.span` is empty and ends directly in front of the `*`,
117 // so we need to extend it by one byte.
119 use_path.span.with_hi(use_path.span.hi() + BytePos(1)),
123 // In this case, the `use_path.span` ends right before the `::*`, so we need to
124 // extend it up to the `*`. Since it is hard to find the `*` in weird
125 // formattings like `use _ :: *;`, we extend it up to, but not including the
126 // `;`. In nested imports, like `use _::{inner::*, _}` there is no `;` and we
127 // can just use the end of the item span
128 let mut span = use_path.span.with_hi(item.span.hi());
129 if snippet(cx, span, "").ends_with(';') {
130 span = use_path.span.with_hi(item.span.hi() - BytePos(1));
137 let imports_string = if used_imports.len() == 1 {
138 used_imports.iter().next().unwrap().to_string()
140 let mut imports = used_imports
142 .map(ToString::to_string)
143 .collect::<Vec<_>>();
148 format!("{{{}}}", imports.join(", "))
152 let sugg = if braced_glob {
155 format!("{}::{}", import_source_snippet, imports_string)
158 let (lint, message) = if let Res::Def(DefKind::Enum, _) = use_path.res {
159 (ENUM_GLOB_USE, "usage of wildcard import for enum variants")
161 (WILDCARD_IMPORTS, "usage of wildcard import")
177 fn check_item_post(&mut self, _: &LateContext<'_, '_>, item: &Item<'_>) {
178 if is_test_module_or_function(item) {
179 self.test_modules_deep = self.test_modules_deep.saturating_sub(1);
184 impl WildcardImports {
185 fn check_exceptions(&self, item: &Item<'_>, segments: &[PathSegment<'_>]) -> bool {
187 || is_prelude_import(segments)
188 || (is_super_only_import(segments) && self.test_modules_deep > 0)
192 // Allow "...prelude::*" imports.
193 // Many crates have a prelude, and it is imported as a glob by design.
194 fn is_prelude_import(segments: &[PathSegment<'_>]) -> bool {
198 .map_or(false, |ps| ps.ident.as_str() == "prelude")
201 // Allow "super::*" imports in tests.
202 fn is_super_only_import(segments: &[PathSegment<'_>]) -> bool {
203 segments.len() == 1 && segments[0].ident.as_str() == "super"
206 fn is_test_module_or_function(item: &Item<'_>) -> bool {
207 matches!(item.kind, ItemKind::Mod(..)) && item.ident.name.as_str().contains("test")