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|
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, symbol::kw, InnerSpan, Span, Symbol};
declare_lint! {
/// The `non_fmt_panic` lint detects `panic!(..)` invocations where the first
/// argument is not a formatting string.
///
/// ### Example
///
/// ```rust,no_run
/// panic!("{}");
/// panic!(123);
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// In Rust 2018 and earlier, `panic!(x)` directly uses `x` as the message.
/// That means that `panic!("{}")` panics with the message `"{}"` instead
/// of using it as a formatting string, and `panic!(123)` will panic with
/// an `i32` as message.
///
/// Rust 2021 always interprets the first argument as format string.
NON_FMT_PANIC,
Warn,
"detect single-argument panic!() invocations in which the argument is not a format string",
report_in_external_macro
}
declare_lint_pass!(NonPanicFmt => [NON_FMT_PANIC]);
impl<'tcx> LateLintPass<'tcx> for NonPanicFmt {
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()
|| Some(def_id) == cx.tcx.lang_items().panic_str()
{
if let Some(id) = f.span.ctxt().outer_expn_data().macro_def_id {
if cx.tcx.is_diagnostic_item(sym::std_panic_2015_macro, id)
|| cx.tcx.is_diagnostic_item(sym::core_panic_2015_macro, id)
{
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 {
// The argument is a string literal.
check_panic_str(cx, f, arg, &sym.as_str());
return;
}
}
// The argument is *not* a string literal.
let (span, panic) = panic_call(cx, f);
cx.struct_span_lint(NON_FMT_PANIC, arg.span, |lint| {
let mut l = lint.build("panic message is not a string literal");
l.note("this is no longer accepted in Rust 2021");
if span.contains(arg.span) {
l.span_suggestion_verbose(
arg.span.shrink_to_lo(),
"add a \"{}\" format string to Display the message",
"\"{}\", ".into(),
Applicability::MaybeIncorrect,
);
if panic == sym::std_panic_macro {
l.span_suggestion_verbose(
span.until(arg.span),
"or use std::panic::panic_any instead",
"std::panic::panic_any(".into(),
Applicability::MachineApplicable,
);
}
}
l.emit();
});
}
fn check_panic_str<'tcx>(
cx: &LateContext<'tcx>,
f: &'tcx hir::Expr<'tcx>,
arg: &'tcx hir::Expr<'tcx>,
fmt: &str,
) {
if !fmt.contains(&['{', '}'][..]) {
// No brace, no problem.
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();
let (span, _) = panic_call(cx, f);
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(NON_FMT_PANIC, 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 Rust 2021");
if span.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(NON_FMT_PANIC, brace_spans.unwrap_or(vec![span]), |lint| {
let mut l = lint.build(msg);
l.note("this message is not used as a format string, but will be in Rust 2021");
if span.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();
});
}
}
fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span, Symbol) {
let mut expn = f.span.ctxt().outer_expn_data();
let mut panic_macro = kw::Empty;
// Unwrap more levels of macro expansion, as panic_2015!()
// was likely expanded from panic!() and possibly from
// [debug_]assert!().
for &i in
&[sym::std_panic_macro, sym::core_panic_macro, 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(i, id)) {
expn = parent;
panic_macro = i;
}
}
(expn.call_site, panic_macro)
}
|
