New upstream version 1.52.1+dfsg1

[rustc.git] / src / tools / clippy / clippy_lints / src / main_recursion.rs

diff --git a/src/tools/clippy/clippy_lints/src/main_recursion.rs b/src/tools/clippy/clippy_lints/src/main_recursion.rs
new file mode 100644 (file)
index 0000000..1b274c7
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/main_recursion.rs
@@ -0,0 +1,61 @@
+use rustc_hir::{Crate, Expr, ExprKind, QPath};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+
+use crate::utils::{is_entrypoint_fn, is_no_std_crate, snippet, span_lint_and_help};
+use if_chain::if_chain;
+
+declare_clippy_lint! {
+    /// **What it does:** Checks for recursion using the entrypoint.
+    ///
+    /// **Why is this bad?** Apart from special setups (which we could detect following attributes like #![no_std]),
+    /// recursing into main() seems like an unintuitive antipattern we should be able to detect.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    /// ```no_run
+    /// fn main() {
+    ///     main();
+    /// }
+    /// ```
+    pub MAIN_RECURSION,
+    style,
+    "recursion using the entrypoint"
+}
+
+#[derive(Default)]
+pub struct MainRecursion {
+    has_no_std_attr: bool,
+}
+
+impl_lint_pass!(MainRecursion => [MAIN_RECURSION]);
+
+impl LateLintPass<'_> for MainRecursion {
+    fn check_crate(&mut self, cx: &LateContext<'_>, _: &Crate<'_>) {
+        self.has_no_std_attr = is_no_std_crate(cx);
+    }
+
+    fn check_expr_post(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
+        if self.has_no_std_attr {
+            return;
+        }
+
+        if_chain! {
+            if let ExprKind::Call(func, _) = &expr.kind;
+            if let ExprKind::Path(QPath::Resolved(_, path)) = &func.kind;
+            if let Some(def_id) = path.res.opt_def_id();
+            if is_entrypoint_fn(cx, def_id);
+            then {
+                span_lint_and_help(
+                    cx,
+                    MAIN_RECURSION,
+                    func.span,
+                    &format!("recursing into entrypoint `{}`", snippet(cx, func.span, "main")),
+                    None,
+                    "consider using another function for this recursion"
+                )
+            }
+        }
+    }
+}