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Auto merge of rust-lang#78088 - fusion-engineering-forks:panic-fmt-li…
…nt, r=estebank
Add lint for panic!("{}")
This adds a lint that warns about `panic!("{}")`.
`panic!(msg)` invocations with a single argument use their argument as panic payload literally, without using it as a format string. The same holds for `assert!(expr, msg)`.
This lints checks if `msg` is a string literal (after expansion), and warns in case it contained braces. It suggests to insert `"{}", ` to use the message literally, or to add arguments to use it as a format string.
This lint is also a good starting point for adding warnings about `panic!(not_a_string)` later, once [`panic_any()`](rust-lang#74622) becomes a stable alternative.- Loading branch information
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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}; | ||
|
|
||
| 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]); | ||
|
|
||
| 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) | ||
| { | ||
| let fmt = sym.as_str(); | ||
| if !fmt.contains(&['{', '}'][..]) { | ||
| return; | ||
| } | ||
|
|
||
| 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!(). | ||
| 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; | ||
| } | ||
| } | ||
|
|
||
| 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(), | ||
| 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, | ||
| ); | ||
| } | ||
| 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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