bjoernager/rust
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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()