1 files changed, 71 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/manual_assert.rs b/src/tools/clippy/clippy_lints/src/manual_assert.rs
new file mode 100644
index 000000000..26b53ab5d
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/manual_assert.rs
@@ -0,0 +1,71 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::macros::{root_macro_call, FormatArgsExpn};
+use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::{peel_blocks_with_stmt, sugg};
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind, UnOp};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::sym;
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Detects `if`-then-`panic!` that can be replaced with `assert!`.
+    ///
+    /// ### Why is this bad?
+    /// `assert!` is simpler than `if`-then-`panic!`.
+    ///
+    /// ### Example
+    /// ```rust
+    /// let sad_people: Vec<&str> = vec![];
+    /// if !sad_people.is_empty() {
+    ///     panic!("there are sad people: {:?}", sad_people);
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// let sad_people: Vec<&str> = vec![];
+    /// assert!(sad_people.is_empty(), "there are sad people: {:?}", sad_people);
+    /// ```
+    #[clippy::version = "1.57.0"]
+    pub MANUAL_ASSERT,
+    pedantic,
+    "`panic!` and only a `panic!` in `if`-then statement"
+}
+
+declare_lint_pass!(ManualAssert => [MANUAL_ASSERT]);
+
+impl<'tcx> LateLintPass<'tcx> for ManualAssert {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
+        if_chain! {
+            if let ExprKind::If(cond, then, None) = expr.kind;
+            if !matches!(cond.kind, ExprKind::Let(_));
+            if !expr.span.from_expansion();
+            let then = peel_blocks_with_stmt(then);
+            if let Some(macro_call) = root_macro_call(then.span);
+            if cx.tcx.item_name(macro_call.def_id) == sym::panic;
+            if !cx.tcx.sess.source_map().is_multiline(cond.span);
+            if let Some(format_args) = FormatArgsExpn::find_nested(cx, then, macro_call.expn);
+            then {
+                let mut applicability = Applicability::MachineApplicable;
+                let format_args_snip = snippet_with_applicability(cx, format_args.inputs_span(), "..", &mut applicability);
+                let cond = cond.peel_drop_temps();
+                let (cond, not) = match cond.kind {
+                    ExprKind::Unary(UnOp::Not, e) => (e, ""),
+                    _ => (cond, "!"),
+                };
+                let cond_sugg = sugg::Sugg::hir_with_applicability(cx, cond, "..", &mut applicability).maybe_par();
+                let sugg = format!("assert!({not}{cond_sugg}, {format_args_snip});");
+                span_lint_and_sugg(
+                    cx,
+                    MANUAL_ASSERT,
+                    expr.span,
+                    "only a `panic!` in `if`-then statement",
+                    "try",
+                    sugg,
+                    Applicability::MachineApplicable,
+                );
+            }
+        }
+    }
+}