clippy_lints/src/macro_use.rs

   1 use crate::utils::{snippet, span_lint_and_sugg};
   2 use if_chain::if_chain;
   3 use rustc_ast::ast;
   4 use rustc_errors::Applicability;
   5 use rustc_lint::{EarlyContext, EarlyLintPass};
   6 use rustc_session::{declare_lint_pass, declare_tool_lint};
   7 use rustc_span::edition::Edition;
   8
   9 declare_clippy_lint! {
  10     /// **What it does:** Checks for `#[macro_use] use...`.
  11     ///
  12     /// **Why is this bad?** Since the Rust 2018 edition you can import
  13     /// macro's directly, this is considered idiomatic.
  14     ///
  15     /// **Known problems:** This lint does not generate an auto-applicable suggestion.
  16     ///
  17     /// **Example:**
  18     /// ```rust
  19     /// #[macro_use]
  20     /// use lazy_static;
  21     /// ```
  22     pub MACRO_USE_IMPORTS,
  23     pedantic,
  24     "#[macro_use] is no longer needed"
  25 }
  26
  27 declare_lint_pass!(MacroUseImports => [MACRO_USE_IMPORTS]);
  28
  29 impl EarlyLintPass for MacroUseImports {
  30     fn check_item(&mut self, ecx: &EarlyContext<'_>, item: &ast::Item) {
  31         if_chain! {
  32             if ecx.sess.opts.edition == Edition::Edition2018;
  33             if let ast::ItemKind::Use(use_tree) = &item.kind;
  34             if let Some(mac_attr) = item
  35                 .attrs
  36                 .iter()
  37                 .find(|attr| attr.ident().map(|s| s.to_string()) == Some("macro_use".to_string()));
  38             then {
  39                 let msg = "`macro_use` attributes are no longer needed in the Rust 2018 edition";
  40                 let help = format!("use {}::<macro name>", snippet(ecx, use_tree.span, "_"));
  41                 span_lint_and_sugg(
  42                     ecx,
  43                     MACRO_USE_IMPORTS,
  44                     mac_attr.span,
  45                     msg,
  46                     "remove the attribute and import the macro directly, try",
  47                     help,
  48                     Applicability::HasPlaceholders,
  49                 );
  50             }
  51         }
  52     }
  53 }