Fix #518

src/panic.rs

@@ -0,0 +1,42 @@
+use rustc::lint::*;
+use rustc_front::hir::*;
+use syntax::ast::Lit_::LitStr;
+
+use utils::{span_lint, in_external_macro, match_path, BEGIN_UNWIND};
+
+/// **What it does:** Warn about missing parameters in `panic!`.
+///
+/// **Known problems:** Should you want to use curly brackets in `panic!` without any parameter,
+/// this lint will warn.
+///
+/// **Example:**
+/// ```
+/// panic!("This panic! is probably missing a parameter there: {}");
+/// ```
+declare_lint!(pub PANIC_PARAMS, Warn, "missing parameters in `panic!`");
+
+#[allow(missing_copy_implementations)]
+pub struct PanicPass;
+
+impl LintPass for PanicPass {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(PANIC_PARAMS)
+    }
+}
+
+impl LateLintPass for PanicPass {
+    fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
+        if_let_chain! {[
+            in_external_macro(cx, expr.span),
+            let ExprCall(ref fun, ref params) = expr.node,
+            params.len() == 2,
+            let ExprPath(None, ref path) = fun.node,
+            match_path(path, &BEGIN_UNWIND),
+            let ExprLit(ref lit) = params[0].node,
+            let LitStr(ref string, _) = lit.node,
+            string.contains('{')
+        ], {
+            span_lint(cx, PANIC_PARAMS, expr.span, "You probably are missing some parameter in your `panic!` call");
+        }}
+    }
+}