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! {
16 /// **What it does:** Checks for `use Enum::*`.
18 /// **Why is this bad?** It is usually better style to use the prefixed name of
19 /// an enumeration variant, rather than importing variants.
21 /// **Known problems:** Old-style enumerations that prefix the variants are
27 /// use std::cmp::Ordering::*;
31 /// use std::cmp::Ordering;
32 /// foo(Ordering::Less)
36 "use items that import all variants of an enum"
39 declare_clippy_lint! {
40 /// **What it does:** Checks for wildcard imports `use _::*`.
42 /// **Why is this bad?** wildcard imports can pollute the namespace. This is especially bad if
43 /// you try to import something through a wildcard, that already has been imported by name from
44 /// a different source:
47 /// use crate1::foo; // Imports a function named foo
48 /// use crate2::*; // Has a function named foo
50 /// foo(); // Calls crate1::foo
53 /// This can lead to confusing error messages at best and to unexpected behavior at worst.
57 /// Wildcard imports are allowed from modules named `prelude`. Many crates (including the standard library)
58 /// provide modules named "prelude" specifically designed for wildcard import.
60 /// `use super::*` is allowed in test modules. This is defined as any module with "test" in the name.
62 /// These exceptions can be disabled using the `warn-on-all-wildcard-imports` configuration flag.
64 /// **Known problems:** If macros are imported through the wildcard, this macro is not included
65 /// by the suggestion and has to be added by hand.
67 /// Applying the suggestion when explicit imports of the things imported with a glob import
68 /// exist, may result in `unused_imports` warnings.
87 "lint `use _::*` statements"
91 pub struct WildcardImports {
93 test_modules_deep: u32,
96 impl WildcardImports {
97 pub fn new(warn_on_all: bool) -> Self {
100 test_modules_deep: 0,
105 impl_lint_pass!(WildcardImports => [ENUM_GLOB_USE, WILDCARD_IMPORTS]);
107 impl LateLintPass<'_> for WildcardImports {
108 fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
109 if is_test_module_or_function(cx.tcx, item) {
110 self.test_modules_deep = self.test_modules_deep.saturating_add(1);
112 if item.vis.node.is_pub() || item.vis.node.is_pub_restricted() {
116 if let ItemKind::Use(use_path, UseKind::Glob) = &item.kind;
117 if self.warn_on_all || !self.check_exceptions(item, use_path.segments);
118 let used_imports = cx.tcx.names_imported_by_glob_use(item.def_id);
119 if !used_imports.is_empty(); // Already handled by `unused_imports`
121 let mut applicability = Applicability::MachineApplicable;
122 let import_source_snippet = snippet_with_applicability(cx, use_path.span, "..", &mut applicability);
123 let (span, braced_glob) = if import_source_snippet.is_empty() {
124 // This is a `_::{_, *}` import
125 // In this case `use_path.span` is empty and ends directly in front of the `*`,
126 // so we need to extend it by one byte.
128 use_path.span.with_hi(use_path.span.hi() + BytePos(1)),
132 // In this case, the `use_path.span` ends right before the `::*`, so we need to
133 // extend it up to the `*`. Since it is hard to find the `*` in weird
134 // formattings like `use _ :: *;`, we extend it up to, but not including the
135 // `;`. In nested imports, like `use _::{inner::*, _}` there is no `;` and we
136 // can just use the end of the item span
137 let mut span = use_path.span.with_hi(item.span.hi());
138 if snippet(cx, span, "").ends_with(';') {
139 span = use_path.span.with_hi(item.span.hi() - BytePos(1));
146 let imports_string = if used_imports.len() == 1 {
147 used_imports.iter().next().unwrap().to_string()
149 let mut imports = used_imports
151 .map(ToString::to_string)
152 .collect::<Vec<_>>();
157 format!("{{{}}}", imports.join(", "))
161 let sugg = if braced_glob {
164 format!("{}::{}", import_source_snippet, imports_string)
167 let (lint, message) = if let Res::Def(DefKind::Enum, _) = use_path.res {
168 (ENUM_GLOB_USE, "usage of wildcard import for enum variants")
170 (WILDCARD_IMPORTS, "usage of wildcard import")
186 fn check_item_post(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
187 if is_test_module_or_function(cx.tcx, item) {
188 self.test_modules_deep = self.test_modules_deep.saturating_sub(1);
193 impl WildcardImports {
194 fn check_exceptions(&self, item: &Item<'_>, segments: &[PathSegment<'_>]) -> bool {
196 || is_prelude_import(segments)
197 || (is_super_only_import(segments) && self.test_modules_deep > 0)
201 // Allow "...prelude::..::*" imports.
202 // Many crates have a prelude, and it is imported as a glob by design.
203 fn is_prelude_import(segments: &[PathSegment<'_>]) -> bool {
204 segments.iter().any(|ps| ps.ident.name == sym::prelude)
207 // Allow "super::*" imports in tests.
208 fn is_super_only_import(segments: &[PathSegment<'_>]) -> bool {
209 segments.len() == 1 && segments[0].ident.name == kw::Super