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Rollup merge of #88954 - nbdd0121:panic3, r=oli-obk

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Allow `panic!("{}", computed_str)` in const fn.

Special-case `panic!("{}", arg)` and translate it to `panic_display(&arg)`. `panic_display` will behave like `panic_any` in cosnt eval and behave like `panic!(format_args!("{}", arg))` in runtime.

This should bring Rust 2015 and 2021 to feature parity in terms of `const_panic`; and hopefully would unblock the stabilisation of #51999.

`@rustbot` modify labels: +T-compiler +T-libs +A-const-eval +A-const-fn

r? `@oli-obk`
This commit is contained in:
Guillaume Gomez 2021-09-17 17:41:19 +02:00 • committed by GitHub
commit eb62779f2d
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GPG key ID: 4AEE18F83AFDEB23
14 changed files with 135 additions and 46 deletions
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9
compiler/rustc_const_eval/src/const_eval/machine.rs
View file

@ -36,12 +36,17 @@ impl<'mir, 'tcx> InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>> {
let def_id = instance.def_id();
if Some(def_id) == self.tcx.lang_items().panic_fn()
|| Some(def_id) == self.tcx.lang_items().panic_str()
|| Some(def_id) == self.tcx.lang_items().panic_display()
|| Some(def_id) == self.tcx.lang_items().begin_panic_fn()
{
// &str
// &str or &&str
assert!(args.len() == 1);
let msg_place = self.deref_operand(&args[0])?;
let mut msg_place = self.deref_operand(&args[0])?;
while msg_place.layout.ty.is_ref() {
msg_place = self.deref_operand(&msg_place.into())?;
}
let msg = Symbol::intern(self.read_str(&msg_place)?);
let span = self.find_closest_untracked_caller_location();
let (file, line, col) = self.location_triple_for_span(span);

13
compiler/rustc_const_eval/src/transform/check_consts/check.rs
View file

@ -888,6 +888,10 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
if is_lang_panic_fn(tcx, callee) {
self.check_op(ops::Panic);
// `begin_panic` and `panic_display` are generic functions that accept
// types other than str. Check to enforce that only str can be used in
// const-eval.
// const-eval of the `begin_panic` fn assumes the argument is `&str`
if Some(callee) == tcx.lang_items().begin_panic_fn() {
match args[0].ty(&self.ccx.body.local_decls, tcx).kind() {
@ -896,6 +900,15 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
}
}
// const-eval of the `panic_display` fn assumes the argument is `&&str`
if Some(callee) == tcx.lang_items().panic_display() {
match args[0].ty(&self.ccx.body.local_decls, tcx).kind() {
ty::Ref(_, ty, _) if matches!(ty.kind(), ty::Ref(_, ty, _) if ty.is_str()) =>
{}
_ => self.check_op(ops::PanicNonStr),
}
}
return;
}

1
compiler/rustc_const_eval/src/transform/check_consts/mod.rs
View file

@ -79,6 +79,7 @@ pub fn is_lang_panic_fn(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
// Keep in sync with what that function handles!
Some(def_id) == tcx.lang_items().panic_fn()
|| Some(def_id) == tcx.lang_items().panic_str()
|| Some(def_id) == tcx.lang_items().panic_display()
|| Some(def_id) == tcx.lang_items().begin_panic_fn()
|| Some(def_id) == tcx.lang_items().panic_fmt()
|| Some(def_id) == tcx.lang_items().begin_panic_fmt()

1
compiler/rustc_hir/src/lang_items.rs
View file

@ -283,6 +283,7 @@ language_item_table! {
// a weak lang item, but do not have it defined.
Panic, sym::panic, panic_fn, Target::Fn, GenericRequirement::None;
PanicFmt, sym::panic_fmt, panic_fmt, Target::Fn, GenericRequirement::None;
PanicDisplay, sym::panic_display, panic_display, Target::Fn, GenericRequirement::None;
PanicStr, sym::panic_str, panic_str, Target::Fn, GenericRequirement::None;
ConstPanicFmt, sym::const_panic_fmt, const_panic_fmt, Target::Fn, GenericRequirement::None;
PanicBoundsCheck, sym::panic_bounds_check, panic_bounds_check_fn, Target::Fn, GenericRequirement::None;

1
compiler/rustc_span/src/symbol.rs
View file

@ -923,6 +923,7 @@ symbols! {
panic_2021,
panic_abort,
panic_bounds_check,
panic_display,
panic_fmt,
panic_handler,
panic_impl,

9
library/core/src/panic.rs
View file

@ -27,9 +27,14 @@ pub macro panic_2015 {
($msg:literal $(,)?) => (
$crate::panicking::panic($msg)
),
// Use `panic_str` instead of `panic_display::<&str>` for non_fmt_panic lint.
($msg:expr $(,)?) => (
$crate::panicking::panic_str($msg)
),
// Special-case the single-argument case for const_panic.
("{}", $arg:expr $(,)?) => (
$crate::panicking::panic_display(&$arg)
),
($fmt:expr, $($arg:tt)+) => (
$crate::panicking::panic_fmt($crate::const_format_args!($fmt, $($arg)+))
),
@ -44,6 +49,10 @@ pub macro panic_2021 {
() => (
$crate::panicking::panic("explicit panic")
),
// Special-case the single-argument case for const_panic.
("{}", $arg:expr $(,)?) => (
$crate::panicking::panic_display(&$arg)
),
($($t:tt)+) => (
$crate::panicking::panic_fmt($crate::const_format_args!($($t)+))
),

7
library/core/src/panicking.rs
View file

@ -60,6 +60,13 @@ pub fn panic_str(expr: &str) -> ! {
panic_fmt(format_args!("{}", expr));
}
#[inline]
#[track_caller]
#[cfg_attr(not(bootstrap), lang = "panic_display")] // needed for const-evaluated panics
pub fn panic_display<T: fmt::Display>(x: &T) -> ! {
panic_fmt(format_args!("{}", *x));
}
#[cold]
#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
#[track_caller]

1
library/std/src/lib.rs
View file

@ -258,6 +258,7 @@
#![feature(const_trait_impl)]
#![feature(container_error_extra)]
#![feature(core_intrinsics)]
#![feature(core_panic)]
#![feature(custom_test_frameworks)]
#![feature(decl_macro)]
#![feature(doc_cfg)]

6
library/std/src/panic.rs
View file

@ -10,7 +10,7 @@ use crate::thread::Result;
#[doc(hidden)]
#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
#[allow_internal_unstable(libstd_sys_internals, const_format_args)]
#[allow_internal_unstable(libstd_sys_internals, const_format_args, core_panic)]
#[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_2015_macro")]
#[rustc_macro_transparency = "semitransparent"]
pub macro panic_2015 {
@ -20,6 +20,10 @@ pub macro panic_2015 {
($msg:expr $(,)?) => ({
$crate::rt::begin_panic($msg)
}),
// Special-case the single-argument case for const_panic.
("{}", $arg:expr $(,)?) => ({
$crate::rt::panic_display(&$arg)
}),
($fmt:expr, $($arg:tt)+) => ({
$crate::rt::begin_panic_fmt(&$crate::const_format_args!($fmt, $($arg)+))
}),

1
library/std/src/rt.rs
View file

@ -16,6 +16,7 @@
// Re-export some of our utilities which are expected by other crates.
pub use crate::panicking::{begin_panic, begin_panic_fmt, panic_count};
pub use core::panicking::panic_display;
// To reduce the generated code of the new `lang_start`, this function is doing
// the real work.

8
src/test/ui/consts/const-eval/const_panic.rs
View file

@ -15,10 +15,13 @@ const Y: () = std::unreachable!();
const X: () = std::unimplemented!();
//~^ ERROR evaluation of constant value failed
//
const W: () = std::panic!(MSG);
//~^ ERROR evaluation of constant value failed
const W2: () = std::panic!("{}", MSG);
//~^ ERROR evaluation of constant value failed
const Z_CORE: () = core::panic!("cheese");
//~^ ERROR evaluation of constant value failed
@ -33,3 +36,6 @@ const X_CORE: () = core::unimplemented!();
const W_CORE: () = core::panic!(MSG);
//~^ ERROR evaluation of constant value failed
const W2_CORE: () = core::panic!("{}", MSG);
//~^ ERROR evaluation of constant value failed

50
src/test/ui/consts/const-eval/const_panic.stderr
View file

@ -39,45 +39,61 @@ LL | const W: () = std::panic!(MSG);
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic.rs:22:20
--> $DIR/const_panic.rs:22:16
|
LL | const W2: () = std::panic!("{}", MSG);
| ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:22:16
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic.rs:25:20
|
LL | const Z_CORE: () = core::panic!("cheese");
| ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'cheese', $DIR/const_panic.rs:22:20
| ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'cheese', $DIR/const_panic.rs:25:20
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic.rs:25:21
--> $DIR/const_panic.rs:28:21
|
LL | const Z2_CORE: () = core::panic!();
| ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic.rs:25:21
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic.rs:28:20
|
LL | const Y_CORE: () = core::unreachable!();
| ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic.rs:28:20
| ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic.rs:28:21
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic.rs:31:20
|
LL | const X_CORE: () = core::unimplemented!();
| ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic.rs:31:20
LL | const Y_CORE: () = core::unreachable!();
| ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic.rs:31:20
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic.rs:34:20
|
LL | const W_CORE: () = core::panic!(MSG);
| ^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:34:20
LL | const X_CORE: () = core::unimplemented!();
| ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic.rs:34:20
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 10 previous errors
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic.rs:37:20
|
LL | const W_CORE: () = core::panic!(MSG);
| ^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:37:20
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic.rs:40:21
|
LL | const W2_CORE: () = core::panic!("{}", MSG);
| ^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:40:21
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 12 previous errors
For more information about this error, try `rustc --explain E0080`.

16
src/test/ui/consts/const-eval/const_panic_2021.rs
View file

@ -2,6 +2,8 @@
#![feature(const_panic)]
#![crate_type = "lib"]
const MSG: &str = "hello";
const A: () = std::panic!("blåhaj");
//~^ ERROR evaluation of constant value failed
@ -14,14 +16,20 @@ const C: () = std::unreachable!();
const D: () = std::unimplemented!();
//~^ ERROR evaluation of constant value failed
const E: () = core::panic!("shark");
const E: () = std::panic!("{}", MSG);
//~^ ERROR evaluation of constant value failed
const F: () = core::panic!();
const A_CORE: () = core::panic!("shark");
//~^ ERROR evaluation of constant value failed
const G: () = core::unreachable!();
const B_CORE: () = core::panic!();
//~^ ERROR evaluation of constant value failed
const H: () = core::unimplemented!();
const C_CORE: () = core::unreachable!();
//~^ ERROR evaluation of constant value failed
const D_CORE: () = core::unimplemented!();
//~^ ERROR evaluation of constant value failed
const E_CORE: () = core::panic!("{}", MSG);
//~^ ERROR evaluation of constant value failed

58
src/test/ui/consts/const-eval/const_panic_2021.stderr
View file

@ -1,67 +1,83 @@
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:5:15
--> $DIR/const_panic_2021.rs:7:15
|
LL | const A: () = std::panic!("blåhaj");
| ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'blåhaj', $DIR/const_panic_2021.rs:5:15
| ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'blåhaj', $DIR/const_panic_2021.rs:7:15
|
= note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:8:15
--> $DIR/const_panic_2021.rs:10:15
|
LL | const B: () = std::panic!();
| ^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic_2021.rs:8:15
| ^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic_2021.rs:10:15
|
= note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:11:15
--> $DIR/const_panic_2021.rs:13:15
|
LL | const C: () = std::unreachable!();
| ^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic_2021.rs:11:15
| ^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic_2021.rs:13:15
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:14:15
--> $DIR/const_panic_2021.rs:16:15
|
LL | const D: () = std::unimplemented!();
| ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic_2021.rs:14:15
| ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic_2021.rs:16:15
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:17:15
--> $DIR/const_panic_2021.rs:19:15
|
LL | const E: () = core::panic!("shark");
| ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'shark', $DIR/const_panic_2021.rs:17:15
LL | const E: () = std::panic!("{}", MSG);
| ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic_2021.rs:19:15
|
= note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:20:15
--> $DIR/const_panic_2021.rs:22:20
|
LL | const F: () = core::panic!();
| ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic_2021.rs:20:15
LL | const A_CORE: () = core::panic!("shark");
| ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'shark', $DIR/const_panic_2021.rs:22:20
|
= note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:23:15
--> $DIR/const_panic_2021.rs:25:20
|
LL | const G: () = core::unreachable!();
| ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic_2021.rs:23:15
LL | const B_CORE: () = core::panic!();
| ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic_2021.rs:25:20
|
= note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:28:20
|
LL | const C_CORE: () = core::unreachable!();
| ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic_2021.rs:28:20
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:26:15
--> $DIR/const_panic_2021.rs:31:20
|
LL | const H: () = core::unimplemented!();
| ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic_2021.rs:26:15
LL | const D_CORE: () = core::unimplemented!();
| ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'not implemented', $DIR/const_panic_2021.rs:31:20
|
= note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 8 previous errors
error[E0080]: evaluation of constant value failed
--> $DIR/const_panic_2021.rs:34:20
|
LL | const E_CORE: () = core::panic!("{}", MSG);
| ^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic_2021.rs:34:20
|
= note: this error originates in the macro `$crate::panic::panic_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 10 previous errors
For more information about this error, try `rustc --explain E0080`.