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Rollup merge of #76739 - davidtwco:issue-75323-non-static-lifetime-in-anonconst, r=varkor

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resolve: prohibit anon const non-static lifetimes

Fixes #75323, fixes #74447 and fixes #73375.

This PR prohibits non-static lifetimes in anonymous constants when only the `min_const_generics` feature is enabled. ~~To do so, `to_region_vid`'s `bug!` had to be changed into a delayed bug, which unfortunately required providing it a `TyCtxt`.~~

---
~~While I am happy with how the implementation of the error turned out in `rustc_passes::check_const`,  emitting an error wasn't sufficient to avoid hitting the ICE later. I also tried implementing the error in `rustc_mir::transform::check_consts::validation` and that worked, but it didn't silence the ICE either. To silence the ICE, I changed it to a delayed bug which worked but was more invasive that I would have liked, and required I return an incorrect lifetime. It's possible that this check should be implemented earlier in the compiler to make the invasive changes unnecessary, but I wasn't sure where that would be and wanted to get some feedback first.~~
The approach taken by this PR has been changed to implement the error in name resolution, which ended up being much simpler.

cc @rust-lang/wg-const-eval
r? @lcnr
This commit is contained in:
Jonas Schievink 2020-10-02 20:26:55 +02:00 • committed by GitHub
commit c8eb2059da
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29
compiler/rustc_resolve/src/late/diagnostics.rs
View file

@ -16,6 +16,7 @@ use rustc_hir::def::{self, CtorKind, DefKind};
use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
use rustc_hir::PrimTy;
use rustc_session::config::nightly_options;
use rustc_session::parse::feature_err;
use rustc_span::hygiene::MacroKind;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{BytePos, Span, DUMMY_SP};
@ -1599,4 +1600,32 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
_ => {}
}
}
/// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics` so
/// this function will emit an error if `min_const_generics` is enabled, the body identified by
/// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
crate fn maybe_emit_forbidden_non_static_lifetime_error(
&self,
body_id: hir::BodyId,
lifetime_ref: &'tcx hir::Lifetime,
) {
let is_anon_const = matches!(
self.tcx.def_kind(self.tcx.hir().body_owner_def_id(body_id)),
hir::def::DefKind::AnonConst
);
let is_allowed_lifetime = matches!(
lifetime_ref.name,
hir::LifetimeName::Implicit | hir::LifetimeName::Static | hir::LifetimeName::Underscore
);
if self.tcx.features().min_const_generics && is_anon_const && !is_allowed_lifetime {
feature_err(
&self.tcx.sess.parse_sess,
sym::const_generics,
lifetime_ref.span,
"a non-static lifetime is not allowed in a `const`",
)
.emit();
}
}
}

4
compiler/rustc_resolve/src/late/lifetimes.rs
View file

@ -1777,6 +1777,10 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
let result = loop {
match *scope {
Scope::Body { id, s } => {
// Non-static lifetimes are prohibited in anonymous constants under
// `min_const_generics`.
self.maybe_emit_forbidden_non_static_lifetime_error(id, lifetime_ref);
outermost_body = Some(id);
scope = s;
}