Add lint for panic!("{}") #78088
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,150 @@ | ||
| use crate::{LateContext, LateLintPass, LintContext}; | ||
| use rustc_ast as ast; | ||
| use rustc_errors::{pluralize, Applicability}; | ||
| use rustc_hir as hir; | ||
| use rustc_middle::ty; | ||
| use rustc_parse_format::{ParseMode, Parser, Piece}; | ||
| use rustc_span::{sym, InnerSpan}; | ||
|
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| declare_lint! { | ||
| /// The `panic_fmt` lint detects `panic!("..")` with `{` or `}` in the string literal. | ||
| /// | ||
| /// ### Example | ||
| /// | ||
| /// ```rust,no_run | ||
| /// panic!("{}"); | ||
| /// ``` | ||
| /// | ||
| /// {{produces}} | ||
| /// | ||
| /// ### Explanation | ||
| /// | ||
| /// `panic!("{}")` panics with the message `"{}"`, as a `panic!()` invocation | ||
| /// with a single argument does not use `format_args!()`. | ||
| /// A future edition of Rust will interpret this string as format string, | ||
| /// which would break this. | ||
| PANIC_FMT, | ||
| Warn, | ||
| "detect braces in single-argument panic!() invocations", | ||
| report_in_external_macro | ||
| } | ||
|
|
||
| declare_lint_pass!(PanicFmt => [PANIC_FMT]); | ||
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|
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| impl<'tcx> LateLintPass<'tcx> for PanicFmt { | ||
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) { | ||
| if let hir::ExprKind::Call(f, [arg]) = &expr.kind { | ||
| if let &ty::FnDef(def_id, _) = cx.typeck_results().expr_ty(f).kind() { | ||
| if Some(def_id) == cx.tcx.lang_items().begin_panic_fn() | ||
| || Some(def_id) == cx.tcx.lang_items().panic_fn() | ||
| { | ||
| check_panic(cx, f, arg); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tcx hir::Expr<'tcx>) { | ||
| if let hir::ExprKind::Lit(lit) = &arg.kind { | ||
| if let ast::LitKind::Str(sym, _) = lit.node { | ||
| let mut expn = f.span.ctxt().outer_expn_data(); | ||
| if let Some(id) = expn.macro_def_id { | ||
| if cx.tcx.is_diagnostic_item(sym::std_panic_macro, id) | ||
| || cx.tcx.is_diagnostic_item(sym::core_panic_macro, id) | ||
| { | ||
|
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There was a problem hiding this comment. A common approach I take to avoid deeply nested let lit = match &arg.kind {
hir::ExprKind::Lit(lit) => lit,
_ => return,
};
}Not necessary to do that now. There was a problem hiding this comment. The |
||
| let fmt = sym.as_str(); | ||
| if !fmt.contains(&['{', '}'][..]) { | ||
| return; | ||
| } | ||
|
|
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| let fmt_span = arg.span.source_callsite(); | ||
|
|
||
| let (snippet, style) = | ||
| match cx.sess().parse_sess.source_map().span_to_snippet(fmt_span) { | ||
| Ok(snippet) => { | ||
| // Count the number of `#`s between the `r` and `"`. | ||
| let style = snippet.strip_prefix('r').and_then(|s| s.find('"')); | ||
| (Some(snippet), style) | ||
| } | ||
| Err(_) => (None, None), | ||
| }; | ||
|
|
||
| let mut fmt_parser = | ||
| Parser::new(fmt.as_ref(), style, snippet.clone(), false, ParseMode::Format); | ||
| let n_arguments = | ||
| (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count(); | ||
|
|
||
| // Unwrap another level of macro expansion if this panic!() | ||
| // was expanded from assert!() or debug_assert!(). | ||
|
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There was a problem hiding this comment. What would happen if a crate I depend on has a There was a problem hiding this comment. That shows the warning, but not any suggestions (because it doesn't know if extra arguments can be added to |
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| for &assert in &[sym::assert_macro, sym::debug_assert_macro] { | ||
| let parent = expn.call_site.ctxt().outer_expn_data(); | ||
| if parent | ||
| .macro_def_id | ||
| .map_or(false, |id| cx.tcx.is_diagnostic_item(assert, id)) | ||
| { | ||
| expn = parent; | ||
| } | ||
| } | ||
|
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||
| if n_arguments > 0 && fmt_parser.errors.is_empty() { | ||
| let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] { | ||
| [] => vec![fmt_span], | ||
| v => v.iter().map(|span| fmt_span.from_inner(*span)).collect(), | ||
| }; | ||
| cx.struct_span_lint(PANIC_FMT, arg_spans, |lint| { | ||
| let mut l = lint.build(match n_arguments { | ||
| 1 => "panic message contains an unused formatting placeholder", | ||
| _ => "panic message contains unused formatting placeholders", | ||
| }); | ||
| l.note("this message is not used as a format string when given without arguments, but will be in a future Rust edition"); | ||
| if expn.call_site.contains(arg.span) { | ||
| l.span_suggestion( | ||
| arg.span.shrink_to_hi(), | ||
| &format!("add the missing argument{}", pluralize!(n_arguments)), | ||
| ", ...".into(), | ||
|
There was a problem hiding this comment. Could we use There was a problem hiding this comment. That's tricky to get right. For example: |
||
| Applicability::HasPlaceholders, | ||
| ); | ||
| l.span_suggestion( | ||
| arg.span.shrink_to_lo(), | ||
| "or add a \"{}\" format string to use the message literally", | ||
| "\"{}\", ".into(), | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
| l.emit(); | ||
| }); | ||
| } else { | ||
| let brace_spans: Option<Vec<_>> = snippet | ||
| .filter(|s| s.starts_with('"') || s.starts_with("r#")) | ||
| .map(|s| { | ||
| s.char_indices() | ||
| .filter(|&(_, c)| c == '{' || c == '}') | ||
| .map(|(i, _)| { | ||
| fmt_span.from_inner(InnerSpan { start: i, end: i + 1 }) | ||
| }) | ||
| .collect() | ||
| }); | ||
| let msg = match &brace_spans { | ||
| Some(v) if v.len() == 1 => "panic message contains a brace", | ||
| _ => "panic message contains braces", | ||
| }; | ||
| cx.struct_span_lint(PANIC_FMT, brace_spans.unwrap_or(vec![expn.call_site]), |lint| { | ||
| let mut l = lint.build(msg); | ||
| l.note("this message is not used as a format string, but will be in a future Rust edition"); | ||
| if expn.call_site.contains(arg.span) { | ||
| l.span_suggestion( | ||
| arg.span.shrink_to_lo(), | ||
| "add a \"{}\" format string to use the message literally", | ||
| "\"{}\", ".into(), | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
|
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There was a problem hiding this comment. I'm guessing this is relevant when the panic is being called inside of a separate macro. Could we maybe account for the cases of that being in a local macro to suggest modifying the original macro in this way and if it is from an external macro to ask the crate writer to do so (or maybe just to mention that a newer version of the crate might have solved it)? For that later case we might just want not to emit this lint at all (at least at first). There was a problem hiding this comment. Hm, that might just not be worth the effort. Let's see how much breaks with the |
||
| l.emit(); | ||
| }); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,6 @@ | ||
| #[macro_export] | ||
| macro_rules! fancy_panic { | ||
| ($msg:expr) => { | ||
| panic!($msg) | ||
| }; | ||
| } |
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