src/tools/clippy/clippy_lints/src/unnecessary_self_imports.rs

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use rustc_ast::{Item, ItemKind, UseTreeKind};
   3 use rustc_errors::Applicability;
   4 use rustc_lint::{EarlyContext, EarlyLintPass};
   5 use rustc_session::declare_lint_pass;
   6 use rustc_span::symbol::kw;
   7
   8 declare_clippy_lint! {
   9     /// ### What it does
  10     /// Checks for imports ending in `::{self}`.
  11     ///
  12     /// ### Why is this bad?
  13     /// In most cases, this can be written much more cleanly by omitting `::{self}`.
  14     ///
  15     /// ### Known problems
  16     /// Removing `::{self}` will cause any non-module items at the same path to also be imported.
  17     /// This might cause a naming conflict (https://github.com/rust-lang/rustfmt/issues/3568). This lint makes no attempt
  18     /// to detect this scenario and that is why it is a restriction lint.
  19     ///
  20     /// ### Example
  21     /// ```no_run
  22     /// use std::io::{self};
  23     /// ```
  24     /// Use instead:
  25     /// ```no_run
  26     /// use std::io;
  27     /// ```
  28     #[clippy::version = "1.53.0"]
  29     pub UNNECESSARY_SELF_IMPORTS,
  30     restriction,
  31     "imports ending in `::{self}`, which can be omitted"
  32 }
  33
  34 declare_lint_pass!(UnnecessarySelfImports => [UNNECESSARY_SELF_IMPORTS]);
  35
  36 impl EarlyLintPass for UnnecessarySelfImports {
  37     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
  38         if let ItemKind::Use(use_tree) = &item.kind
  39             && let UseTreeKind::Nested(nodes) = &use_tree.kind
  40             && let [(self_tree, _)] = &**nodes
  41             && let [self_seg] = &*self_tree.prefix.segments
  42             && self_seg.ident.name == kw::SelfLower
  43             && let Some(last_segment) = use_tree.prefix.segments.last()
  44         {
  45             span_lint_and_then(
  46                 cx,
  47                 UNNECESSARY_SELF_IMPORTS,
  48                 item.span,
  49                 "import ending with `::{self}`",
  50                 |diag| {
  51                     diag.span_suggestion(
  52                         last_segment.span().with_hi(item.span.hi()),
  53                         "consider omitting `::{self}`",
  54                         format!(
  55                             "{}{};",
  56                             last_segment.ident,
  57                             if let UseTreeKind::Simple(Some(alias)) = self_tree.kind {
  58                                 format!(" as {alias}")
  59                             } else {
  60                                 String::new()
  61                             },
  62                         ),
  63                         Applicability::MaybeIncorrect,
  64                     );
  65                     diag.note("this will slightly change semantics; any non-module items at the same path will also be imported");
  66                 },
  67             );
  68         }
  69     }
  70 }