src/tools/clippy/clippy_lints/src/main_recursion.rs

   1 use clippy_utils::diagnostics::span_lint_and_help;
   2 use clippy_utils::source::snippet;
   3 use clippy_utils::{is_entrypoint_fn, is_no_std_crate};
   4 use rustc_hir::{Expr, ExprKind, QPath};
   5 use rustc_lint::{LateContext, LateLintPass};
   6 use rustc_session::impl_lint_pass;
   7
   8 declare_clippy_lint! {
   9     /// ### What it does
  10     /// Checks for recursion using the entrypoint.
  11     ///
  12     /// ### Why is this bad?
  13     /// Apart from special setups (which we could detect following attributes like #![no_std]),
  14     /// recursing into main() seems like an unintuitive anti-pattern we should be able to detect.
  15     ///
  16     /// ### Example
  17     /// ```no_run
  18     /// fn main() {
  19     ///     main();
  20     /// }
  21     /// ```
  22     #[clippy::version = "1.38.0"]
  23     pub MAIN_RECURSION,
  24     style,
  25     "recursion using the entrypoint"
  26 }
  27
  28 #[derive(Default)]
  29 pub struct MainRecursion {
  30     has_no_std_attr: bool,
  31 }
  32
  33 impl_lint_pass!(MainRecursion => [MAIN_RECURSION]);
  34
  35 impl LateLintPass<'_> for MainRecursion {
  36     fn check_crate(&mut self, cx: &LateContext<'_>) {
  37         self.has_no_std_attr = is_no_std_crate(cx);
  38     }
  39
  40     fn check_expr_post(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
  41         if self.has_no_std_attr {
  42             return;
  43         }
  44
  45         if let ExprKind::Call(func, _) = &expr.kind
  46             && let ExprKind::Path(QPath::Resolved(_, path)) = &func.kind
  47             && let Some(def_id) = path.res.opt_def_id()
  48             && is_entrypoint_fn(cx, def_id)
  49         {
  50             span_lint_and_help(
  51                 cx,
  52                 MAIN_RECURSION,
  53                 func.span,
  54                 format!("recursing into entrypoint `{}`", snippet(cx, func.span, "main")),
  55                 None,
  56                 "consider using another function for this recursion",
  57             );
  58         }
  59     }
  60 }