Skip to content

Commit

Permalink
Auto merge of rust-lang#78088 - fusion-engineering-forks:panic-fmt-li…
Browse files Browse the repository at this point in the history
…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.

![image](https://user-images.githubusercontent.com/783247/96643867-79eb1080-1328-11eb-8d4e-a5586837c70a.png)

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
bors committed Nov 20, 2020
2 parents 4ec27e4 + a125ef2 commit 74285eb
Show file tree
Hide file tree
Showing 22 changed files with 362 additions and 165 deletions.
1 change: 1 addition & 0 deletions Cargo.lock
Original file line number Diff line number Diff line change
Expand Up @@ -3831,6 +3831,7 @@ dependencies = [
"rustc_hir",
"rustc_index",
"rustc_middle",
"rustc_parse_format",
"rustc_session",
"rustc_span",
"rustc_target",
Expand Down
52 changes: 30 additions & 22 deletions compiler/rustc_builtin_macros/src/assert.rs
Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
use rustc_errors::{Applicability, DiagnosticBuilder};

use rustc_ast::ptr::P;
use rustc_ast::token::{self, TokenKind};
use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree};
use rustc_ast::token;
use rustc_ast::tokenstream::{DelimSpan, TokenStream};
use rustc_ast::{self as ast, *};
use rustc_ast_pretty::pprust;
use rustc_expand::base::*;
Expand All @@ -26,31 +26,39 @@ pub fn expand_assert<'cx>(
// `core::panic` and `std::panic` are different macros, so we use call-site
// context to pick up whichever is currently in scope.
let sp = cx.with_call_site_ctxt(sp);
let tokens = custom_message.unwrap_or_else(|| {
TokenStream::from(TokenTree::token(
TokenKind::lit(
token::Str,

let panic_call = if let Some(tokens) = custom_message {
// Pass the custom message to panic!().
cx.expr(
sp,
ExprKind::MacCall(MacCall {
path: Path::from_ident(Ident::new(sym::panic, sp)),
args: P(MacArgs::Delimited(
DelimSpan::from_single(sp),
MacDelimiter::Parenthesis,
tokens,
)),
prior_type_ascription: None,
}),
)
} else {
// Pass our own message directly to $crate::panicking::panic(),
// because it might contain `{` and `}` that should always be
// passed literally.
cx.expr_call_global(
sp,
cx.std_path(&[sym::panicking, sym::panic]),
vec![cx.expr_str(
DUMMY_SP,
Symbol::intern(&format!(
"assertion failed: {}",
pprust::expr_to_string(&cond_expr).escape_debug()
)),
None,
),
DUMMY_SP,
))
});
let args = P(MacArgs::Delimited(DelimSpan::from_single(sp), MacDelimiter::Parenthesis, tokens));
let panic_call = MacCall {
path: Path::from_ident(Ident::new(sym::panic, sp)),
args,
prior_type_ascription: None,
)],
)
};
let if_expr = cx.expr_if(
sp,
cx.expr(sp, ExprKind::Unary(UnOp::Not, cond_expr)),
cx.expr(sp, ExprKind::MacCall(panic_call)),
None,
);
let if_expr =
cx.expr_if(sp, cx.expr(sp, ExprKind::Unary(UnOp::Not, cond_expr)), panic_call, None);
MacEager::expr(if_expr)
}

Expand Down
3 changes: 2 additions & 1 deletion compiler/rustc_expand/src/mbe/macro_rules.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1173,7 +1173,8 @@ fn quoted_tt_to_string(tt: &mbe::TokenTree) -> String {
mbe::TokenTree::MetaVar(_, name) => format!("${}", name),
mbe::TokenTree::MetaVarDecl(_, name, kind) => format!("${}:{}", name, kind),
_ => panic!(
"unexpected mbe::TokenTree::{{Sequence or Delimited}} \
"{}",
"unexpected mbe::TokenTree::{Sequence or Delimited} \
in follow set checker"
),
}
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_lint/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -20,3 +20,4 @@ rustc_feature = { path = "../rustc_feature" }
rustc_index = { path = "../rustc_index" }
rustc_session = { path = "../rustc_session" }
rustc_trait_selection = { path = "../rustc_trait_selection" }
rustc_parse_format = { path = "../rustc_parse_format" }
3 changes: 3 additions & 0 deletions compiler/rustc_lint/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ mod levels;
mod methods;
mod non_ascii_idents;
mod nonstandard_style;
mod panic_fmt;
mod passes;
mod redundant_semicolon;
mod traits;
Expand All @@ -80,6 +81,7 @@ use internal::*;
use methods::*;
use non_ascii_idents::*;
use nonstandard_style::*;
use panic_fmt::PanicFmt;
use redundant_semicolon::*;
use traits::*;
use types::*;
Expand Down Expand Up @@ -166,6 +168,7 @@ macro_rules! late_lint_passes {
ClashingExternDeclarations: ClashingExternDeclarations::new(),
DropTraitConstraints: DropTraitConstraints,
TemporaryCStringAsPtr: TemporaryCStringAsPtr,
PanicFmt: PanicFmt,
]
);
};
Expand Down
150 changes: 150 additions & 0 deletions compiler/rustc_lint/src/panic_fmt.rs
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();
});
}
}
}
}
}
}
4 changes: 4 additions & 0 deletions compiler/rustc_passes/src/diagnostic_items.rs
Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,10 @@ fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> FxHashMap<Symbol, DefId> {
}
}

for m in tcx.hir().krate().exported_macros {
collector.observe_item(m.attrs, m.hir_id);
}

collector.items
}

Expand Down
5 changes: 5 additions & 0 deletions compiler/rustc_span/src/symbol.rs
Original file line number Diff line number Diff line change
Expand Up @@ -267,6 +267,7 @@ symbols! {
asm,
assert,
assert_inhabited,
assert_macro,
assert_receiver_is_total_eq,
assert_uninit_valid,
assert_zero_valid,
Expand Down Expand Up @@ -393,6 +394,7 @@ symbols! {
copysignf64,
core,
core_intrinsics,
core_panic_macro,
cosf32,
cosf64,
crate_id,
Expand All @@ -416,6 +418,7 @@ symbols! {
dead_code,
dealloc,
debug,
debug_assert_macro,
debug_assertions,
debug_struct,
debug_trait,
Expand Down Expand Up @@ -789,6 +792,7 @@ symbols! {
panic_runtime,
panic_str,
panic_unwind,
panicking,
param_attrs,
parent_trait,
partial_cmp,
Expand Down Expand Up @@ -1064,6 +1068,7 @@ symbols! {
staticlib,
std,
std_inject,
std_panic_macro,
stmt,
stmt_expr_attributes,
stop_after_dataflow,
Expand Down
4 changes: 4 additions & 0 deletions library/core/src/macros/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
#[macro_export]
#[allow_internal_unstable(core_panic, const_caller_location)]
#[stable(feature = "core", since = "1.6.0")]
#[cfg_attr(not(bootstrap), rustc_diagnostic_item = "core_panic_macro")]
macro_rules! panic {
() => (
$crate::panic!("explicit panic")
Expand Down Expand Up @@ -162,6 +163,7 @@ macro_rules! assert_ne {
/// ```
#[macro_export]
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(bootstrap), rustc_diagnostic_item = "debug_assert_macro")]
macro_rules! debug_assert {
($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert!($($arg)*); })
}
Expand Down Expand Up @@ -1215,6 +1217,8 @@ pub(crate) mod builtin {
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_builtin_macro]
#[macro_export]
#[cfg_attr(not(bootstrap), rustc_diagnostic_item = "assert_macro")]
#[allow_internal_unstable(core_panic)]
macro_rules! assert {
($cond:expr $(,)?) => {{ /* compiler built-in */ }};
($cond:expr, $($arg:tt)+) => {{ /* compiler built-in */ }};
Expand Down
2 changes: 1 addition & 1 deletion library/core/tests/nonzero.rs
Original file line number Diff line number Diff line change
Expand Up @@ -85,7 +85,7 @@ fn test_match_option_string() {
let five = "Five".to_string();
match Some(five) {
Some(s) => assert_eq!(s, "Five"),
None => panic!("unexpected None while matching on Some(String { ... })"),
None => panic!("{}", "unexpected None while matching on Some(String { ... })"),
}
}

Expand Down
1 change: 1 addition & 0 deletions library/std/src/macros.rs
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
#[macro_export]
#[stable(feature = "rust1", since = "1.0.0")]
#[allow_internal_unstable(libstd_sys_internals)]
#[cfg_attr(not(any(bootstrap, test)), rustc_diagnostic_item = "std_panic_macro")]
macro_rules! panic {
() => ({ $crate::panic!("explicit panic") });
($msg:expr $(,)?) => ({ $crate::rt::begin_panic($msg) });
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@
let mut _8: bool; // in scope 0 at $DIR/inst_combine_deref.rs:60:5: 60:23
let mut _9: bool; // in scope 0 at $DIR/inst_combine_deref.rs:60:13: 60:21
let mut _10: i32; // in scope 0 at $DIR/inst_combine_deref.rs:60:13: 60:15
let mut _11: !; // in scope 0 at $SRC_DIR/std/src/macros.rs:LL:COL
let mut _11: !; // in scope 0 at $DIR/inst_combine_deref.rs:60:5: 60:23
scope 1 {
debug x => _1; // in scope 1 at $DIR/inst_combine_deref.rs:55:9: 55:10
let _2: i32; // in scope 1 at $DIR/inst_combine_deref.rs:56:9: 56:10
Expand Down Expand Up @@ -69,11 +69,11 @@
}

bb2: {
StorageLive(_11); // scope 4 at $SRC_DIR/std/src/macros.rs:LL:COL
begin_panic::<&str>(const "assertion failed: *y == 99"); // scope 4 at $SRC_DIR/std/src/macros.rs:LL:COL
StorageLive(_11); // scope 4 at $DIR/inst_combine_deref.rs:60:5: 60:23
core::panicking::panic(const "assertion failed: *y == 99"); // scope 4 at $DIR/inst_combine_deref.rs:60:5: 60:23
// mir::Constant
// + span: $SRC_DIR/std/src/macros.rs:LL:COL
// + literal: Const { ty: fn(&str) -> ! {std::rt::begin_panic::<&str>}, val: Value(Scalar(<ZST>)) }
// + span: $DIR/inst_combine_deref.rs:60:5: 60:23
// + literal: Const { ty: fn(&'static str) -> ! {core::panicking::panic}, val: Value(Scalar(<ZST>)) }
// ty::Const
// + ty: &str
// + val: Value(Slice { data: Allocation { bytes: [97, 115, 115, 101, 114, 116, 105, 111, 110, 32, 102, 97, 105, 108, 101, 100, 58, 32, 42, 121, 32, 61, 61, 32, 57, 57], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [67108863], len: Size { raw: 26 } }, size: Size { raw: 26 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 26 })
Expand Down
6 changes: 6 additions & 0 deletions src/test/ui/auxiliary/fancy-panic.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
#[macro_export]
macro_rules! fancy_panic {
($msg:expr) => {
panic!($msg)
};
}
Loading

0 comments on commit 74285eb

Please sign in to comment.