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, |lint| {
123 let mut l = lint.build(fluent::lint::non_fmt_panic);
124 l.set_arg("name", symbol);
125 l.note(fluent::lint::note);
126 l.note(fluent::lint::more_info_note);
127 if !is_arg_inside_call(arg_span, span) {
128 // No clue where this argument is coming from.
132 if arg_macro.map_or(false, |id| cx.tcx.is_diagnostic_item(sym::format_macro, id)) {
133 // A case of `panic!(format!(..))`.
134 l.note(fluent::lint::supports_fmt_note);
135 if let Some((open, close, _)) = find_delimiters(cx, arg_span) {
136 l.multipart_suggestion(
137 fluent::lint::supports_fmt_suggestion,
139 (arg_span.until(open.shrink_to_hi()), "".into()),
140 (close.until(arg_span.shrink_to_hi()), "".into()),
142 Applicability::MachineApplicable,
146 let ty = cx.typeck_results().expr_ty(arg);
147 // If this is a &str or String, we can confidently give the `"{}", ` suggestion.
148 let is_str = matches!(
150 ty::Ref(_, r, _) if *r.kind() == ty::Str,
153 Some(ty_def) if cx.tcx.is_diagnostic_item(sym::String, ty_def.did()),
156 let (suggest_display, suggest_debug) = cx.tcx.infer_ctxt().enter(|infcx| {
158 || cx.tcx.get_diagnostic_item(sym::Display).map(|t| {
160 .type_implements_trait(t, ty, InternalSubsts::empty(), cx.param_env)
164 && cx.tcx.get_diagnostic_item(sym::Debug).map(|t| {
166 .type_implements_trait(t, ty, InternalSubsts::empty(), cx.param_env)
172 let suggest_panic_any = !is_str && panic == sym::std_panic_macro;
174 let fmt_applicability = if suggest_panic_any {
175 // If we can use panic_any, use that as the MachineApplicable suggestion.
176 Applicability::MaybeIncorrect
178 // If we don't suggest panic_any, using a format string is our best bet.
179 Applicability::MachineApplicable
183 l.span_suggestion_verbose(
184 arg_span.shrink_to_lo(),
185 fluent::lint::display_suggestion,
189 } else if suggest_debug {
191 l.span_suggestion_verbose(
192 arg_span.shrink_to_lo(),
193 fluent::lint::debug_suggestion,
199 if suggest_panic_any {
200 if let Some((open, close, del)) = find_delimiters(cx, span) {
201 l.set_arg("already_suggested", suggest_display || suggest_debug);
202 l.multipart_suggestion(
203 fluent::lint::panic_suggestion,
205 vec![(span.until(open), "std::panic::panic_any".into())]
208 (span.until(open.shrink_to_hi()), "std::panic::panic_any(".into()),
212 Applicability::MachineApplicable,
221 fn check_panic_str<'tcx>(
222 cx: &LateContext<'tcx>,
223 f: &'tcx hir::Expr<'tcx>,
224 arg: &'tcx hir::Expr<'tcx>,
227 if !fmt.contains(&['{', '}']) {
228 // No brace, no problem.
232 let (span, _, _) = panic_call(cx, f);
234 if in_external_macro(cx.sess(), span) && in_external_macro(cx.sess(), arg.span) {
235 // Nothing that can be done about it in the current crate.
239 let fmt_span = arg.span.source_callsite();
241 let (snippet, style) = match cx.sess().parse_sess.source_map().span_to_snippet(fmt_span) {
243 // Count the number of `#`s between the `r` and `"`.
244 let style = snippet.strip_prefix('r').and_then(|s| s.find('"'));
245 (Some(snippet), style)
247 Err(_) => (None, None),
250 let mut fmt_parser = Parser::new(fmt, style, snippet.clone(), false, ParseMode::Format);
251 let n_arguments = (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
253 if n_arguments > 0 && fmt_parser.errors.is_empty() {
254 let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] {
255 [] => vec![fmt_span],
258 .map(|span| fmt_span.from_inner(InnerSpan::new(span.start, span.end)))
261 cx.struct_span_lint(NON_FMT_PANICS, arg_spans, |lint| {
262 let mut l = lint.build(fluent::lint::non_fmt_panic_unused);
263 l.set_arg("count", n_arguments);
264 l.note(fluent::lint::note);
265 if is_arg_inside_call(arg.span, span) {
267 arg.span.shrink_to_hi(),
268 fluent::lint::add_args_suggestion,
270 Applicability::HasPlaceholders,
273 arg.span.shrink_to_lo(),
274 fluent::lint::add_fmt_suggestion,
276 Applicability::MachineApplicable,
282 let brace_spans: Option<Vec<_>> =
283 snippet.filter(|s| s.starts_with('"') || s.starts_with("r#")).map(|s| {
285 .filter(|&(_, c)| c == '{' || c == '}')
286 .map(|(i, _)| fmt_span.from_inner(InnerSpan { start: i, end: i + 1 }))
289 let count = brace_spans.as_ref().map(|v| v.len()).unwrap_or(/* any number >1 */ 2);
290 cx.struct_span_lint(NON_FMT_PANICS, brace_spans.unwrap_or_else(|| vec![span]), |lint| {
291 let mut l = lint.build(fluent::lint::non_fmt_panic_braces);
292 l.set_arg("count", count);
293 l.note(fluent::lint::note);
294 if is_arg_inside_call(arg.span, span) {
296 arg.span.shrink_to_lo(),
297 fluent::lint::suggestion,
299 Applicability::MachineApplicable,
307 /// Given the span of `some_macro!(args);`, gives the span of `(` and `)`,
308 /// and the type of (opening) delimiter used.
309 fn find_delimiters<'tcx>(cx: &LateContext<'tcx>, span: Span) -> Option<(Span, Span, char)> {
310 let snippet = cx.sess().parse_sess.source_map().span_to_snippet(span).ok()?;
311 let (open, open_ch) = snippet.char_indices().find(|&(_, c)| "([{".contains(c))?;
312 let close = snippet.rfind(|c| ")]}".contains(c))?;
314 span.from_inner(InnerSpan { start: open, end: open + 1 }),
315 span.from_inner(InnerSpan { start: close, end: close + 1 }),
320 fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span, Symbol, Symbol) {
321 let mut expn = f.span.ctxt().outer_expn_data();
323 let mut panic_macro = kw::Empty;
325 // Unwrap more levels of macro expansion, as panic_2015!()
326 // was likely expanded from panic!() and possibly from
327 // [debug_]assert!().
329 let parent = expn.call_site.ctxt().outer_expn_data();
330 let Some(id) = parent.macro_def_id else { break };
331 let Some(name) = cx.tcx.get_diagnostic_name(id) else { break };
334 sym::core_panic_macro
335 | sym::std_panic_macro
337 | sym::debug_assert_macro
338 | sym::unreachable_macro
347 if let hygiene::ExpnKind::Macro(_, symbol) = expn.kind { symbol } else { sym::panic };
348 (expn.call_site, panic_macro, macro_symbol)
351 fn is_arg_inside_call(arg: Span, call: Span) -> bool {
352 // We only add suggestions if the argument we're looking at appears inside the
353 // panic call in the source file, to avoid invalid suggestions when macros are involved.
354 // We specifically check for the spans to not be identical, as that happens sometimes when
355 // proc_macros lie about spans and apply the same span to all the tokens they produce.
356 call.contains(arg) && !call.source_equal(arg)