1 use crate::{LateContext, LateLintPass, LintContext};
3 use rustc_errors::{fluent, Applicability};
5 use rustc_infer::infer::TyCtxtInferExt;
6 use rustc_middle::lint::in_external_macro;
8 use rustc_middle::ty::subst::InternalSubsts;
9 use rustc_parse_format::{ParseMode, Parser, Piece};
10 use rustc_session::lint::FutureIncompatibilityReason;
11 use rustc_span::edition::Edition;
12 use rustc_span::{hygiene, sym, symbol::kw, InnerSpan, Span, Symbol};
13 use rustc_trait_selection::infer::InferCtxtExt;
16 /// The `non_fmt_panics` lint detects `panic!(..)` invocations where the first
17 /// argument is not a formatting string.
21 /// ```rust,no_run,edition2018
30 /// In Rust 2018 and earlier, `panic!(x)` directly uses `x` as the message.
31 /// That means that `panic!("{}")` panics with the message `"{}"` instead
32 /// of using it as a formatting string, and `panic!(123)` will panic with
33 /// an `i32` as message.
35 /// Rust 2021 always interprets the first argument as format string.
38 "detect single-argument panic!() invocations in which the argument is not a format string",
39 @future_incompatible = FutureIncompatibleInfo {
40 reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2021),
41 explain_reason: false,
43 report_in_external_macro
46 declare_lint_pass!(NonPanicFmt => [NON_FMT_PANICS]);
48 impl<'tcx> LateLintPass<'tcx> for NonPanicFmt {
49 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
50 if let hir::ExprKind::Call(f, [arg]) = &expr.kind {
51 if let &ty::FnDef(def_id, _) = cx.typeck_results().expr_ty(f).kind() {
52 let f_diagnostic_name = cx.tcx.get_diagnostic_name(def_id);
54 if Some(def_id) == cx.tcx.lang_items().begin_panic_fn()
55 || Some(def_id) == cx.tcx.lang_items().panic_fn()
56 || f_diagnostic_name == Some(sym::panic_str)
58 if let Some(id) = f.span.ctxt().outer_expn_data().macro_def_id {
60 cx.tcx.get_diagnostic_name(id),
61 Some(sym::core_panic_2015_macro | sym::std_panic_2015_macro)
63 check_panic(cx, f, arg);
66 } else if f_diagnostic_name == Some(sym::unreachable_display) {
67 if let Some(id) = f.span.ctxt().outer_expn_data().macro_def_id {
68 if cx.tcx.is_diagnostic_item(sym::unreachable_2015_macro, id) {
72 // This is safe because we checked above that the callee is indeed
73 // unreachable_display
75 // Get the borrowed arg not the borrow
76 hir::ExprKind::AddrOf(ast::BorrowKind::Ref, _, arg) => arg,
77 _ => bug!("call to unreachable_display without borrow"),
88 fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tcx hir::Expr<'tcx>) {
89 if let hir::ExprKind::Lit(lit) = &arg.kind {
90 if let ast::LitKind::Str(sym, _) = lit.node {
91 // The argument is a string literal.
92 check_panic_str(cx, f, arg, sym.as_str());
97 // The argument is *not* a string literal.
99 let (span, panic, symbol) = panic_call(cx, f);
101 if in_external_macro(cx.sess(), span) {
102 // Nothing that can be done about it in the current crate.
106 // Find the span of the argument to `panic!()` or `unreachable!`, before expansion in the
107 // case of `panic!(some_macro!())` or `unreachable!(some_macro!())`.
108 // We don't use source_callsite(), because this `panic!(..)` might itself
109 // be expanded from another macro, in which case we want to stop at that
111 let mut arg_span = arg.span;
112 let mut arg_macro = None;
113 while !span.contains(arg_span) {
114 let expn = arg_span.ctxt().outer_expn_data();
118 arg_macro = expn.macro_def_id;
119 arg_span = expn.call_site;
122 cx.struct_span_lint(NON_FMT_PANICS, arg_span, fluent::lint_non_fmt_panic, |lint| {
123 lint.set_arg("name", symbol);
124 lint.note(fluent::note);
125 lint.note(fluent::more_info_note);
126 if !is_arg_inside_call(arg_span, span) {
127 // No clue where this argument is coming from.
130 if arg_macro.map_or(false, |id| cx.tcx.is_diagnostic_item(sym::format_macro, id)) {
131 // A case of `panic!(format!(..))`.
132 lint.note(fluent::supports_fmt_note);
133 if let Some((open, close, _)) = find_delimiters(cx, arg_span) {
134 lint.multipart_suggestion(
135 fluent::supports_fmt_suggestion,
137 (arg_span.until(open.shrink_to_hi()), "".into()),
138 (close.until(arg_span.shrink_to_hi()), "".into()),
140 Applicability::MachineApplicable,
144 let ty = cx.typeck_results().expr_ty(arg);
145 // If this is a &str or String, we can confidently give the `"{}", ` suggestion.
146 let is_str = matches!(
148 ty::Ref(_, r, _) if *r.kind() == ty::Str,
151 Some(ty_def) if cx.tcx.is_diagnostic_item(sym::String, ty_def.did()),
154 let infcx = cx.tcx.infer_ctxt().build();
155 let suggest_display = is_str
156 || cx.tcx.get_diagnostic_item(sym::Display).map(|t| {
158 .type_implements_trait(t, ty, InternalSubsts::empty(), cx.param_env)
161 let suggest_debug = !suggest_display
162 && cx.tcx.get_diagnostic_item(sym::Debug).map(|t| {
164 .type_implements_trait(t, ty, InternalSubsts::empty(), cx.param_env)
168 let suggest_panic_any = !is_str && panic == sym::std_panic_macro;
170 let fmt_applicability = if suggest_panic_any {
171 // If we can use panic_any, use that as the MachineApplicable suggestion.
172 Applicability::MaybeIncorrect
174 // If we don't suggest panic_any, using a format string is our best bet.
175 Applicability::MachineApplicable
179 lint.span_suggestion_verbose(
180 arg_span.shrink_to_lo(),
181 fluent::display_suggestion,
185 } else if suggest_debug {
186 lint.set_arg("ty", ty);
187 lint.span_suggestion_verbose(
188 arg_span.shrink_to_lo(),
189 fluent::debug_suggestion,
195 if suggest_panic_any {
196 if let Some((open, close, del)) = find_delimiters(cx, span) {
197 lint.set_arg("already_suggested", suggest_display || suggest_debug);
198 lint.multipart_suggestion(
199 fluent::panic_suggestion,
201 vec![(span.until(open), "std::panic::panic_any".into())]
204 (span.until(open.shrink_to_hi()), "std::panic::panic_any(".into()),
208 Applicability::MachineApplicable,
217 fn check_panic_str<'tcx>(
218 cx: &LateContext<'tcx>,
219 f: &'tcx hir::Expr<'tcx>,
220 arg: &'tcx hir::Expr<'tcx>,
223 if !fmt.contains(&['{', '}']) {
224 // No brace, no problem.
228 let (span, _, _) = panic_call(cx, f);
230 if in_external_macro(cx.sess(), span) && in_external_macro(cx.sess(), arg.span) {
231 // Nothing that can be done about it in the current crate.
235 let fmt_span = arg.span.source_callsite();
237 let (snippet, style) = match cx.sess().parse_sess.source_map().span_to_snippet(fmt_span) {
239 // Count the number of `#`s between the `r` and `"`.
240 let style = snippet.strip_prefix('r').and_then(|s| s.find('"'));
241 (Some(snippet), style)
243 Err(_) => (None, None),
246 let mut fmt_parser = Parser::new(fmt, style, snippet.clone(), false, ParseMode::Format);
247 let n_arguments = (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
249 if n_arguments > 0 && fmt_parser.errors.is_empty() {
250 let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] {
251 [] => vec![fmt_span],
254 .map(|span| fmt_span.from_inner(InnerSpan::new(span.start, span.end)))
257 cx.struct_span_lint(NON_FMT_PANICS, arg_spans, fluent::lint_non_fmt_panic_unused, |lint| {
258 lint.set_arg("count", n_arguments);
259 lint.note(fluent::note);
260 if is_arg_inside_call(arg.span, span) {
261 lint.span_suggestion(
262 arg.span.shrink_to_hi(),
263 fluent::add_args_suggestion,
265 Applicability::HasPlaceholders,
267 lint.span_suggestion(
268 arg.span.shrink_to_lo(),
269 fluent::add_fmt_suggestion,
271 Applicability::MachineApplicable,
277 let brace_spans: Option<Vec<_>> =
278 snippet.filter(|s| s.starts_with('"') || s.starts_with("r#")).map(|s| {
280 .filter(|&(_, c)| c == '{' || c == '}')
281 .map(|(i, _)| fmt_span.from_inner(InnerSpan { start: i, end: i + 1 }))
284 let count = brace_spans.as_ref().map(|v| v.len()).unwrap_or(/* any number >1 */ 2);
287 brace_spans.unwrap_or_else(|| vec![span]),
288 fluent::lint_non_fmt_panic_braces,
290 lint.set_arg("count", count);
291 lint.note(fluent::note);
292 if is_arg_inside_call(arg.span, span) {
293 lint.span_suggestion(
294 arg.span.shrink_to_lo(),
297 Applicability::MachineApplicable,
306 /// Given the span of `some_macro!(args);`, gives the span of `(` and `)`,
307 /// and the type of (opening) delimiter used.
308 fn find_delimiters<'tcx>(cx: &LateContext<'tcx>, span: Span) -> Option<(Span, Span, char)> {
309 let snippet = cx.sess().parse_sess.source_map().span_to_snippet(span).ok()?;
310 let (open, open_ch) = snippet.char_indices().find(|&(_, c)| "([{".contains(c))?;
311 let close = snippet.rfind(|c| ")]}".contains(c))?;
313 span.from_inner(InnerSpan { start: open, end: open + 1 }),
314 span.from_inner(InnerSpan { start: close, end: close + 1 }),
319 fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span, Symbol, Symbol) {
320 let mut expn = f.span.ctxt().outer_expn_data();
322 let mut panic_macro = kw::Empty;
324 // Unwrap more levels of macro expansion, as panic_2015!()
325 // was likely expanded from panic!() and possibly from
326 // [debug_]assert!().
328 let parent = expn.call_site.ctxt().outer_expn_data();
329 let Some(id) = parent.macro_def_id else { break };
330 let Some(name) = cx.tcx.get_diagnostic_name(id) else { break };
333 sym::core_panic_macro
334 | sym::std_panic_macro
336 | sym::debug_assert_macro
337 | sym::unreachable_macro
346 if let hygiene::ExpnKind::Macro(_, symbol) = expn.kind { symbol } else { sym::panic };
347 (expn.call_site, panic_macro, macro_symbol)
350 fn is_arg_inside_call(arg: Span, call: Span) -> bool {
351 // We only add suggestions if the argument we're looking at appears inside the
352 // panic call in the source file, to avoid invalid suggestions when macros are involved.
353 // We specifically check for the spans to not be identical, as that happens sometimes when
354 // proc_macros lie about spans and apply the same span to all the tokens they produce.
355 call.contains(arg) && !call.source_equal(arg)