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::symbol::kw;
11 use rustc_span::{sym, BytePos};
13 declare_clippy_lint! {
14 /// **What it does:** Checks for `use Enum::*`.
16 /// **Why is this bad?** It is usually better style to use the prefixed name of
17 /// an enumeration variant, rather than importing variants.
19 /// **Known problems:** Old-style enumerations that prefix the variants are
25 /// use std::cmp::Ordering::*;
29 /// use std::cmp::Ordering;
30 /// foo(Ordering::Less)
34 "use items that import all variants of an enum"
37 declare_clippy_lint! {
38 /// **What it does:** Checks for wildcard imports `use _::*`.
40 /// **Why is this bad?** wildcard imports can pollute the namespace. This is especially bad if
41 /// you try to import something through a wildcard, that already has been imported by name from
42 /// a different source:
45 /// use crate1::foo; // Imports a function named foo
46 /// use crate2::*; // Has a function named foo
48 /// foo(); // Calls crate1::foo
51 /// This can lead to confusing error messages at best and to unexpected behavior at worst.
55 /// Wildcard imports are allowed from modules named `prelude`. Many crates (including the standard library)
56 /// provide modules named "prelude" specifically designed for wildcard import.
58 /// `use super::*` is allowed in test modules. This is defined as any module with "test" in the name.
60 /// These exceptions can be disabled using the `warn-on-all-wildcard-imports` configuration flag.
62 /// **Known problems:** If macros are imported through the wildcard, this macro is not included
63 /// by the suggestion and has to be added by hand.
65 /// Applying the suggestion when explicit imports of the things imported with a glob import
66 /// exist, may result in `unused_imports` warnings.
85 "lint `use _::*` statements"
89 pub struct WildcardImports {
91 test_modules_deep: u32,
94 impl WildcardImports {
95 pub fn new(warn_on_all: bool) -> Self {
103 impl_lint_pass!(WildcardImports => [ENUM_GLOB_USE, WILDCARD_IMPORTS]);
105 impl LateLintPass<'_> for WildcardImports {
106 fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
107 if is_test_module_or_function(item) {
108 self.test_modules_deep = self.test_modules_deep.saturating_add(1);
110 if item.vis.node.is_pub() || item.vis.node.is_pub_restricted() {
114 if let ItemKind::Use(use_path, UseKind::Glob) = &item.kind;
115 if self.warn_on_all || !self.check_exceptions(item, use_path.segments);
116 let used_imports = cx.tcx.names_imported_by_glob_use(item.hir_id.owner);
117 if !used_imports.is_empty(); // Already handled by `unused_imports`
119 let mut applicability = Applicability::MachineApplicable;
120 let import_source_snippet = snippet_with_applicability(cx, use_path.span, "..", &mut applicability);
121 let (span, braced_glob) = if import_source_snippet.is_empty() {
122 // This is a `_::{_, *}` import
123 // In this case `use_path.span` is empty and ends directly in front of the `*`,
124 // so we need to extend it by one byte.
126 use_path.span.with_hi(use_path.span.hi() + BytePos(1)),
130 // In this case, the `use_path.span` ends right before the `::*`, so we need to
131 // extend it up to the `*`. Since it is hard to find the `*` in weird
132 // formattings like `use _ :: *;`, we extend it up to, but not including the
133 // `;`. In nested imports, like `use _::{inner::*, _}` there is no `;` and we
134 // can just use the end of the item span
135 let mut span = use_path.span.with_hi(item.span.hi());
136 if snippet(cx, span, "").ends_with(';') {
137 span = use_path.span.with_hi(item.span.hi() - BytePos(1));
144 let imports_string = if used_imports.len() == 1 {
145 used_imports.iter().next().unwrap().to_string()
147 let mut imports = used_imports
149 .map(ToString::to_string)
150 .collect::<Vec<_>>();
155 format!("{{{}}}", imports.join(", "))
159 let sugg = if braced_glob {
162 format!("{}::{}", import_source_snippet, imports_string)
165 let (lint, message) = if let Res::Def(DefKind::Enum, _) = use_path.res {
166 (ENUM_GLOB_USE, "usage of wildcard import for enum variants")
168 (WILDCARD_IMPORTS, "usage of wildcard import")
184 fn check_item_post(&mut self, _: &LateContext<'_>, item: &Item<'_>) {
185 if is_test_module_or_function(item) {
186 self.test_modules_deep = self.test_modules_deep.saturating_sub(1);
191 impl WildcardImports {
192 fn check_exceptions(&self, item: &Item<'_>, segments: &[PathSegment<'_>]) -> bool {
194 || is_prelude_import(segments)
195 || (is_super_only_import(segments) && self.test_modules_deep > 0)
199 // Allow "...prelude::..::*" imports.
200 // Many crates have a prelude, and it is imported as a glob by design.
201 fn is_prelude_import(segments: &[PathSegment<'_>]) -> bool {
202 segments.iter().any(|ps| ps.ident.name == sym::prelude)
205 // Allow "super::*" imports in tests.
206 fn is_super_only_import(segments: &[PathSegment<'_>]) -> bool {
207 segments.len() == 1 && segments[0].ident.name == kw::Super
210 fn is_test_module_or_function(item: &Item<'_>) -> bool {
211 matches!(item.kind, ItemKind::Mod(..)) && item.ident.name.as_str().contains("test")