diff --git a/src/librustc_error_codes/error_codes.rs b/src/librustc_error_codes/error_codes.rs index bbbd8359f0126..279c65ce03d2d 100644 --- a/src/librustc_error_codes/error_codes.rs +++ b/src/librustc_error_codes/error_codes.rs @@ -453,6 +453,7 @@ E0767: include_str!("./error_codes/E0767.md"), E0768: include_str!("./error_codes/E0768.md"), E0769: include_str!("./error_codes/E0769.md"), E0770: include_str!("./error_codes/E0770.md"), +E0771: include_str!("./error_codes/E0771.md"), ; // E0006, // merged with E0005 // E0008, // cannot bind by-move into a pattern guard diff --git a/src/librustc_error_codes/error_codes/E0771.md b/src/librustc_error_codes/error_codes/E0771.md new file mode 100644 index 0000000000000..824a955f6b3f4 --- /dev/null +++ b/src/librustc_error_codes/error_codes/E0771.md @@ -0,0 +1,23 @@ +A non-`'static` lifetime was used in a const generic. This is currently not +allowed. + +Erroneous code example: + +```compile_fail,E0771 +#![feature(const_generics)] + +fn function_with_str<'a, const STRING: &'a str>() {} // error! +``` + +To fix this issue, the lifetime in the const generic need to be changed to +`'static`: + +``` +#![feature(const_generics)] + +fn function_with_str() {} // ok! +``` + +For more information, see [GitHub issue #74052]. + +[GitHub issue #74052]: https://github.com/rust-lang/rust/issues/74052 diff --git a/src/librustc_resolve/late/diagnostics.rs b/src/librustc_resolve/late/diagnostics.rs index 9323c15a94109..c86b414184759 100644 --- a/src/librustc_resolve/late/diagnostics.rs +++ b/src/librustc_resolve/late/diagnostics.rs @@ -1141,6 +1141,24 @@ impl<'tcx> LifetimeContext<'_, 'tcx> { err.emit(); } + // FIXME(const_generics): This patches over a ICE caused by non-'static lifetimes in const + // generics. We are disallowing this until we can decide on how we want to handle non-'static + // lifetimes in const generics. See issue #74052 for discussion. + crate fn emit_non_static_lt_in_const_generic_error(&self, lifetime_ref: &hir::Lifetime) { + let mut err = struct_span_err!( + self.tcx.sess, + lifetime_ref.span, + E0771, + "use of non-static lifetime `{}` in const generic", + lifetime_ref + ); + err.note( + "for more information, see issue #74052 \ + ", + ); + err.emit(); + } + crate fn is_trait_ref_fn_scope(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) -> bool { if let def::Res::Def(_, did) = trait_ref.trait_ref.path.res { if [ diff --git a/src/librustc_resolve/late/lifetimes.rs b/src/librustc_resolve/late/lifetimes.rs index 567db8edec9af..6009e48a54f5e 100644 --- a/src/librustc_resolve/late/lifetimes.rs +++ b/src/librustc_resolve/late/lifetimes.rs @@ -173,6 +173,8 @@ crate struct LifetimeContext<'a, 'tcx> { /// Used to disallow the use of in-band lifetimes in `fn` or `Fn` syntax. is_in_fn_syntax: bool, + is_in_const_generic: bool, + /// List of labels in the function/method currently under analysis. labels_in_fn: Vec, @@ -333,6 +335,7 @@ fn krate(tcx: TyCtxt<'_>) -> NamedRegionMap { scope: ROOT_SCOPE, trait_ref_hack: false, is_in_fn_syntax: false, + is_in_const_generic: false, labels_in_fn: vec![], xcrate_object_lifetime_defaults: Default::default(), lifetime_uses: &mut Default::default(), @@ -828,6 +831,10 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> { self.insert_lifetime(lifetime_ref, Region::Static); return; } + if self.is_in_const_generic && lifetime_ref.name != LifetimeName::Error { + self.emit_non_static_lt_in_const_generic_error(lifetime_ref); + return; + } self.resolve_lifetime_ref(lifetime_ref); } @@ -860,8 +867,11 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> { } } GenericParamKind::Const { ref ty, .. } => { + let was_in_const_generic = self.is_in_const_generic; + self.is_in_const_generic = true; walk_list!(self, visit_param_bound, param.bounds); self.visit_ty(&ty); + self.is_in_const_generic = was_in_const_generic; } } } @@ -1317,6 +1327,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { scope: &wrap_scope, trait_ref_hack: self.trait_ref_hack, is_in_fn_syntax: self.is_in_fn_syntax, + is_in_const_generic: self.is_in_const_generic, labels_in_fn, xcrate_object_lifetime_defaults, lifetime_uses, diff --git a/src/test/ui/const-generics/const-argument-non-static-lifetime.rs b/src/test/ui/const-generics/const-argument-non-static-lifetime.rs new file mode 100644 index 0000000000000..bc09ba2ab553b --- /dev/null +++ b/src/test/ui/const-generics/const-argument-non-static-lifetime.rs @@ -0,0 +1,17 @@ +// run-pass + +#![feature(const_generics)] +//~^ WARN the feature `const_generics` is incomplete +#![allow(dead_code)] + +fn test() {} + +fn wow<'a>() -> &'a () { + test::<{ + let _: &'a (); + 3 + }>(); + &() +} + +fn main() {} diff --git a/src/test/ui/const-generics/const-argument-non-static-lifetime.stderr b/src/test/ui/const-generics/const-argument-non-static-lifetime.stderr new file mode 100644 index 0000000000000..53a7550090d44 --- /dev/null +++ b/src/test/ui/const-generics/const-argument-non-static-lifetime.stderr @@ -0,0 +1,11 @@ +warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes + --> $DIR/const-argument-non-static-lifetime.rs:3:12 + | +LL | #![feature(const_generics)] + | ^^^^^^^^^^^^^^ + | + = note: `#[warn(incomplete_features)]` on by default + = note: see issue #44580 for more information + +warning: 1 warning emitted + diff --git a/src/test/ui/error-codes/E0771.rs b/src/test/ui/error-codes/E0771.rs new file mode 100644 index 0000000000000..ba3592719408c --- /dev/null +++ b/src/test/ui/error-codes/E0771.rs @@ -0,0 +1,8 @@ +#![feature(const_generics)] +//~^ WARN the feature `const_generics` is incomplete + +fn function_with_str<'a, const STRING: &'a str>() {} //~ ERROR E0771 + +fn main() { + function_with_str::<"Hello, world!">() +} diff --git a/src/test/ui/error-codes/E0771.stderr b/src/test/ui/error-codes/E0771.stderr new file mode 100644 index 0000000000000..60220be6b57ba --- /dev/null +++ b/src/test/ui/error-codes/E0771.stderr @@ -0,0 +1,20 @@ +warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes + --> $DIR/E0771.rs:1:12 + | +LL | #![feature(const_generics)] + | ^^^^^^^^^^^^^^ + | + = note: `#[warn(incomplete_features)]` on by default + = note: see issue #44580 for more information + +error[E0771]: use of non-static lifetime `'a` in const generic + --> $DIR/E0771.rs:4:41 + | +LL | fn function_with_str<'a, const STRING: &'a str>() {} + | ^^ + | + = note: for more information, see issue #74052 + +error: aborting due to previous error; 1 warning emitted + +For more information about this error, try `rustc --explain E0771`.