clippy_lints/src/exhaustive_items.rs

   1 use crate::utils::{snippet_opt, span_lint_and_help, span_lint_and_sugg};
   2 use if_chain::if_chain;
   3 use rustc_hir::{Item, ItemKind};
   4 use rustc_errors::Applicability;
   5 use rustc_lint::{LateContext, LateLintPass};
   6 use rustc_session::{declare_lint_pass, declare_tool_lint};
   7 use rustc_span::sym;
   8
   9 declare_clippy_lint! {
  10     /// **What it does:** Warns on any exported `enum`s that are not tagged `#[non_exhaustive]`
  11     ///
  12     /// **Why is this bad?** Exhaustive enums are typically fine, but a project which does
  13     /// not wish to make a stability commitment around enums may wish to disable them by default.
  14     ///
  15     /// **Known problems:** None.
  16     ///
  17     /// **Example:**
  18     ///
  19     /// ```rust
  20     /// enum Foo {
  21     ///     Bar,
  22     ///     Baz
  23     /// }
  24     /// ```
  25     /// Use instead:
  26     /// ```rust
  27     /// #[non_exhaustive]
  28     /// enum Foo {
  29     ///     Bar,
  30     ///     Baz
  31     /// }    /// ```
  32     pub EXHAUSTIVE_ENUMS,
  33     restriction,
  34     "default lint description"
  35 }
  36
  37 declare_lint_pass!(ExhaustiveItems => [EXHAUSTIVE_ENUMS]);
  38
  39 impl LateLintPass<'_> for ExhaustiveItems {
  40     fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
  41         if_chain! {
  42             if let ItemKind::Enum(..) = item.kind;
  43             if cx.access_levels.is_exported(item.hir_id);
  44             if !item.attrs.iter().any(|a| a.has_name(sym::non_exhaustive));
  45             then {
  46                 if let Some(snippet) = snippet_opt(cx, item.span) {
  47                     span_lint_and_sugg(
  48                         cx,
  49                         EXHAUSTIVE_ENUMS,
  50                         item.span,
  51                         "enums should not be exhaustive",
  52                         "try adding #[non_exhaustive]",
  53                         format!("#[non_exhaustive]\n{}", snippet),
  54                         Applicability::MaybeIncorrect,
  55                     );
  56                 } else {
  57                     span_lint_and_help(
  58                         cx,
  59                         EXHAUSTIVE_ENUMS,
  60                         item.span,
  61                         "enums should not be exhaustive",
  62                         None,
  63                         "try adding #[non_exhaustive]",
  64                     );
  65                 }
  66             }
  67         }
  68     }
  69 }