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
24 /// use std::cmp::Ordering::*;
28 /// use std::cmp::Ordering;
29 /// foo(Ordering::Less)
33 "use items that import all variants of an enum"
36 declare_clippy_lint! {
37 /// **What it does:** Checks for wildcard imports `use _::*`.
39 /// **Why is this bad?** wildcard imports can pollute the namespace. This is especially bad if
40 /// you try to import something through a wildcard, that already has been imported by name from
41 /// a different source:
44 /// use crate1::foo; // Imports a function named foo
45 /// use crate2::*; // Has a function named foo
47 /// foo(); // Calls crate1::foo
50 /// This can lead to confusing error messages at best and to unexpected behavior at worst.
54 /// Wildcard imports are allowed from modules named `prelude`. Many crates (including the standard library)
55 /// provide modules named "prelude" specifically designed for wildcard import.
57 /// `use super::*` is allowed in test modules. This is defined as any module with "test" in the name.
59 /// These exceptions can be disabled using the `warn-on-all-wildcard-imports` configuration flag.
61 /// **Known problems:** If macros are imported through the wildcard, this macro is not included
62 /// by the suggestion and has to be added by hand.
64 /// Applying the suggestion when explicit imports of the things imported with a glob import
65 /// exist, may result in `unused_imports` warnings.
84 "lint `use _::*` statements"
88 pub struct WildcardImports {
90 test_modules_deep: u32,
93 impl WildcardImports {
94 pub fn new(warn_on_all: bool) -> Self {
102 impl_lint_pass!(WildcardImports => [ENUM_GLOB_USE, WILDCARD_IMPORTS]);
104 impl LateLintPass<'_> for WildcardImports {
105 fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
106 if is_test_module_or_function(item) {
107 self.test_modules_deep = self.test_modules_deep.saturating_add(1);
109 if item.vis.node.is_pub() || item.vis.node.is_pub_restricted() {
113 if let ItemKind::Use(use_path, UseKind::Glob) = &item.kind;
114 if self.warn_on_all || !self.check_exceptions(item, use_path.segments);
115 let used_imports = cx.tcx.names_imported_by_glob_use(item.hir_id.owner);
116 if !used_imports.is_empty(); // Already handled by `unused_imports`
118 let mut applicability = Applicability::MachineApplicable;
119 let import_source_snippet = snippet_with_applicability(cx, use_path.span, "..", &mut applicability);
120 let (span, braced_glob) = if import_source_snippet.is_empty() {
121 // This is a `_::{_, *}` import
122 // In this case `use_path.span` is empty and ends directly in front of the `*`,
123 // so we need to extend it by one byte.
125 use_path.span.with_hi(use_path.span.hi() + BytePos(1)),
129 // In this case, the `use_path.span` ends right before the `::*`, so we need to
130 // extend it up to the `*`. Since it is hard to find the `*` in weird
131 // formattings like `use _ :: *;`, we extend it up to, but not including the
132 // `;`. In nested imports, like `use _::{inner::*, _}` there is no `;` and we
133 // can just use the end of the item span
134 let mut span = use_path.span.with_hi(item.span.hi());
135 if snippet(cx, span, "").ends_with(';') {
136 span = use_path.span.with_hi(item.span.hi() - BytePos(1));
143 let imports_string = if used_imports.len() == 1 {
144 used_imports.iter().next().unwrap().to_string()
146 let mut imports = used_imports
148 .map(ToString::to_string)
149 .collect::<Vec<_>>();
154 format!("{{{}}}", imports.join(", "))
158 let sugg = if braced_glob {
161 format!("{}::{}", import_source_snippet, imports_string)
164 let (lint, message) = if let Res::Def(DefKind::Enum, _) = use_path.res {
165 (ENUM_GLOB_USE, "usage of wildcard import for enum variants")
167 (WILDCARD_IMPORTS, "usage of wildcard import")
183 fn check_item_post(&mut self, _: &LateContext<'_>, item: &Item<'_>) {
184 if is_test_module_or_function(item) {
185 self.test_modules_deep = self.test_modules_deep.saturating_sub(1);
190 impl WildcardImports {
191 fn check_exceptions(&self, item: &Item<'_>, segments: &[PathSegment<'_>]) -> bool {
193 || is_prelude_import(segments)
194 || (is_super_only_import(segments) && self.test_modules_deep > 0)
198 // Allow "...prelude::*" imports.
199 // Many crates have a prelude, and it is imported as a glob by design.
200 fn is_prelude_import(segments: &[PathSegment<'_>]) -> bool {
204 .map_or(false, |ps| ps.ident.as_str() == "prelude")
207 // Allow "super::*" imports in tests.
208 fn is_super_only_import(segments: &[PathSegment<'_>]) -> bool {
209 segments.len() == 1 && segments[0].ident.as_str() == "super"
212 fn is_test_module_or_function(item: &Item<'_>) -> bool {
213 matches!(item.kind, ItemKind::Mod(..)) && item.ident.name.as_str().contains("test")