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Auto merge of #86998 - m-ou-se:const-panic-fmt-as-str, r=oli-obk

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Make const panic!("..") work in Rust 2021.

During const eval, this replaces calls to core::panicking::panic_fmt and std::panicking::being_panic_fmt with a call to a new const fn: core::panicking::const_panic_fmt. That function uses fmt::Arguments::as_str() to get the str and calls panic_str with that instead.

panic!() invocations with formatting arguments are still not accepted, as the creation of such a fmt::Arguments cannot be done in constant functions right now.

r? `@RalfJung`
This commit is contained in:
bors
2021-07-29 07:12:07 +00:00
parent 581b1664c9 312bf8e0b8
commit 6e0a8bf790
17 changed files with 203 additions and 21 deletions
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5
compiler/rustc_mir/src/transform/check_consts/mod.rs
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@@ -74,9 +74,14 @@ impl ConstCx<'mir, 'tcx> {
/// Returns `true` if this `DefId` points to one of the official `panic` lang items.
pub fn is_lang_panic_fn(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
// We can allow calls to these functions because `hook_panic_fn` in
// `const_eval/machine.rs` ensures the calls are handled specially.
// 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().begin_panic_fn()
|| Some(def_id) == tcx.lang_items().panic_fmt()
|| Some(def_id) == tcx.lang_items().begin_panic_fmt()
}
pub fn rustc_allow_const_fn_unstable(