clippy_lints/src/single_component_path_imports.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::in_macro;
   3 use if_chain::if_chain;
   4 use rustc_ast::{Item, ItemKind, UseTreeKind};
   5 use rustc_errors::Applicability;
   6 use rustc_lint::{EarlyContext, EarlyLintPass};
   7 use rustc_session::{declare_lint_pass, declare_tool_lint};
   8 use rustc_span::edition::Edition;
   9
  10 declare_clippy_lint! {
  11     /// **What it does:** Checking for imports with single component use path.
  12     ///
  13     /// **Why is this bad?** Import with single component use path such as `use cratename;`
  14     /// is not necessary, and thus should be removed.
  15     ///
  16     /// **Known problems:** None.
  17     ///
  18     /// **Example:**
  19     ///
  20     /// ```rust,ignore
  21     /// use regex;
  22     ///
  23     /// fn main() {
  24     ///     regex::Regex::new(r"^\d{4}-\d{2}-\d{2}$").unwrap();
  25     /// }
  26     /// ```
  27     /// Better as
  28     /// ```rust,ignore
  29     /// fn main() {
  30     ///     regex::Regex::new(r"^\d{4}-\d{2}-\d{2}$").unwrap();
  31     /// }
  32     /// ```
  33     pub SINGLE_COMPONENT_PATH_IMPORTS,
  34     style,
  35     "imports with single component path are redundant"
  36 }
  37
  38 declare_lint_pass!(SingleComponentPathImports => [SINGLE_COMPONENT_PATH_IMPORTS]);
  39
  40 impl EarlyLintPass for SingleComponentPathImports {
  41     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
  42         if_chain! {
  43             if !in_macro(item.span);
  44             if cx.sess.opts.edition >= Edition::Edition2018;
  45             if !item.vis.kind.is_pub();
  46             if let ItemKind::Use(use_tree) = &item.kind;
  47             if let segments = &use_tree.prefix.segments;
  48             if segments.len() == 1;
  49             if let UseTreeKind::Simple(None, _, _) = use_tree.kind;
  50             then {
  51                 span_lint_and_sugg(
  52                     cx,
  53                     SINGLE_COMPONENT_PATH_IMPORTS,
  54                     item.span,
  55                     "this import is redundant",
  56                     "remove it entirely",
  57                     String::new(),
  58                     Applicability::MachineApplicable
  59                 );
  60             }
  61         }
  62     }
  63 }