Deny non-lifetime bound vars in for<..> || closure binders

compiler/rustc_feature/src/active.rs

@@ -474,7 +474,7 @@ declare_features! (
     /// Allows using the `non_exhaustive_omitted_patterns` lint.
     (active, non_exhaustive_omitted_patterns_lint, "1.57.0", Some(89554), None),
     /// Allows `for<T>` binders in where-clauses
-    (incomplete, non_lifetime_binders, "CURRENT_RUSTC_VERSION", Some(1), None),
+    (incomplete, non_lifetime_binders, "CURRENT_RUSTC_VERSION", Some(108185), None),
     /// Allows making `dyn Trait` well-formed even if `Trait` is not object safe.
     /// In that case, `dyn Trait: Trait` does not hold. Moreover, coercions and
     /// casts in safe Rust to `dyn Trait` for such a `Trait` is also forbidden.

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -252,6 +252,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 // (*) -- not late-bound, won't change
             }
 
+            Some(rbv::ResolvedArg::Error(_)) => {
+                bug!("only ty/ct should resolve as ResolvedArg::Error")
+            }
+
             None => {
                 self.re_infer(def, lifetime.ident.span).unwrap_or_else(|| {
                     debug!(?lifetime, "unelided lifetime in signature");
@@ -2689,6 +2693,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         let index = generics.param_def_id_to_index[&def_id.to_def_id()];
                         tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id))
                     }
+                    Some(rbv::ResolvedArg::Error(guar)) => tcx.ty_error_with_guaranteed(guar),
                     arg => bug!("unexpected bound var resolution for {hir_id:?}: {arg:?}"),
                 }
             }
@@ -2893,22 +2898,14 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             hir::TyKind::BareFn(bf) => {
                 require_c_abi_if_c_variadic(tcx, bf.decl, bf.abi, ast_ty.span);
 
-                let fn_ptr_ty = tcx.mk_fn_ptr(self.ty_of_fn(
+                tcx.mk_fn_ptr(self.ty_of_fn(
                     ast_ty.hir_id,
                     bf.unsafety,
                     bf.abi,
                     bf.decl,
                     None,
                     Some(ast_ty),
-                ));
-
-                if let Some(guar) =
-                    deny_non_region_late_bound(tcx, bf.generic_params, "function pointer")
-                {
-                    tcx.ty_error_with_guaranteed(guar)
-                } else {
-                    fn_ptr_ty
-                }
+                ))
             }
             hir::TyKind::TraitObject(bounds, lifetime, repr) => {
                 self.maybe_lint_bare_trait(ast_ty, in_path);
@@ -2917,21 +2914,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     TraitObjectSyntax::DynStar => ty::DynStar,
                 };
 
-                let object_ty = self.conv_object_ty_poly_trait_ref(
-                    ast_ty.span,
-                    bounds,
-                    lifetime,
-                    borrowed,
-                    repr,
-                );
-
-                if let Some(guar) = bounds.iter().find_map(|trait_ref| {
-                    deny_non_region_late_bound(tcx, trait_ref.bound_generic_params, "trait object")
-                }) {
-                    tcx.ty_error_with_guaranteed(guar)
-                } else {
-                    object_ty
-                }
+                self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime, borrowed, repr)
             }
             hir::TyKind::Path(hir::QPath::Resolved(maybe_qself, path)) => {
                 debug!(?maybe_qself, ?path);
@@ -3392,24 +3375,3 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         }
     }
 }
-
-fn deny_non_region_late_bound(
-    tcx: TyCtxt<'_>,
-    params: &[hir::GenericParam<'_>],
-    where_: &str,
-) -> Option<ErrorGuaranteed> {
-    params.iter().find_map(|bad_param| {
-        let what = match bad_param.kind {
-            hir::GenericParamKind::Type { .. } => "type",
-            hir::GenericParamKind::Const { .. } => "const",
-            hir::GenericParamKind::Lifetime { .. } => return None,
-        };
-
-        let mut diag = tcx.sess.struct_span_err(
-            bad_param.span,
-            format!("late-bound {what} parameter not allowed on {where_} types"),
-        );
-
-        Some(if tcx.features().non_lifetime_binders { diag.emit() } else { diag.delay_as_bug() })
-    })
-}

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -398,7 +398,12 @@ fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<S
                 Some(rbv::ResolvedArg::StaticLifetime | rbv::ResolvedArg::EarlyBound(..)) => {}
                 Some(rbv::ResolvedArg::LateBound(debruijn, _, _))
                     if debruijn < self.outer_index => {}
-                Some(rbv::ResolvedArg::LateBound(..) | rbv::ResolvedArg::Free(..)) | None => {
+                Some(
+                    rbv::ResolvedArg::LateBound(..)
+                    | rbv::ResolvedArg::Free(..)
+                    | rbv::ResolvedArg::Error(_),
+                )
+                | None => {
                     self.has_late_bound_regions = Some(lt.ident.span);
                 }
             }

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -50,7 +50,7 @@ impl RegionExt for ResolvedArg {
 
     fn id(&self) -> Option<DefId> {
         match *self {
-            ResolvedArg::StaticLifetime => None,
+            ResolvedArg::StaticLifetime | ResolvedArg::Error(_) => None,
 
             ResolvedArg::EarlyBound(id)
             | ResolvedArg::LateBound(_, _, id)
@@ -336,7 +336,57 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             }
         }
     }
+
+    fn visit_poly_trait_ref_inner(
+        &mut self,
+        trait_ref: &'tcx hir::PolyTraitRef<'tcx>,
+        non_lifetime_binder_allowed: NonLifetimeBinderAllowed,
+    ) {
+        debug!("visit_poly_trait_ref(trait_ref={:?})", trait_ref);
+
+        let (mut binders, scope_type) = self.poly_trait_ref_binder_info();
+
+        let initial_bound_vars = binders.len() as u32;
+        let mut bound_vars: FxIndexMap<LocalDefId, ResolvedArg> = FxIndexMap::default();
+        let binders_iter =
+            trait_ref.bound_generic_params.iter().enumerate().map(|(late_bound_idx, param)| {
+                let pair = ResolvedArg::late(initial_bound_vars + late_bound_idx as u32, param);
+                let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
+                bound_vars.insert(pair.0, pair.1);
+                r
+            });
+        binders.extend(binders_iter);
+
+        if let NonLifetimeBinderAllowed::Deny(where_) = non_lifetime_binder_allowed {
+            deny_non_region_late_bound(self.tcx, &mut bound_vars, where_);
+        }
+
+        debug!(?binders);
+        self.record_late_bound_vars(trait_ref.trait_ref.hir_ref_id, binders);
+
+        // Always introduce a scope here, even if this is in a where clause and
+        // we introduced the binders around the bounded Ty. In that case, we
+        // just reuse the concatenation functionality also present in nested trait
+        // refs.
+        let scope = Scope::Binder {
+            hir_id: trait_ref.trait_ref.hir_ref_id,
+            bound_vars,
+            s: self.scope,
+            scope_type,
+            where_bound_origin: None,
+        };
+        self.with(scope, |this| {
+            walk_list!(this, visit_generic_param, trait_ref.bound_generic_params);
+            this.visit_trait_ref(&trait_ref.trait_ref);
+        });
+    }
+}
+
+enum NonLifetimeBinderAllowed {
+    Deny(&'static str),
+    Allow,
 }
+
 impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
     type NestedFilter = nested_filter::OnlyBodies;
 
@@ -400,7 +450,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                 }
             }
 
-            let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
+            let (mut bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
                 bound_generic_params
                     .iter()
                     .enumerate()
@@ -411,6 +461,8 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                     })
                     .unzip();
 
+            deny_non_region_late_bound(self.tcx, &mut bound_vars, "closures");
+
             self.record_late_bound_vars(e.hir_id, binders);
             let scope = Scope::Binder {
                 hir_id: e.hir_id,
@@ -567,7 +619,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
     fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
         match ty.kind {
             hir::TyKind::BareFn(c) => {
-                let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) = c
+                let (mut bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) = c
                     .generic_params
                     .iter()
                     .enumerate()
@@ -577,6 +629,9 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                         (pair, r)
                     })
                     .unzip();
+
+                deny_non_region_late_bound(self.tcx, &mut bound_vars, "function pointer types");
+
                 self.record_late_bound_vars(ty.hir_id, binders);
                 let scope = Scope::Binder {
                     hir_id: ty.hir_id,
@@ -596,7 +651,10 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                 let scope = Scope::TraitRefBoundary { s: self.scope };
                 self.with(scope, |this| {
                     for bound in bounds {
-                        this.visit_poly_trait_ref(bound);
+                        this.visit_poly_trait_ref_inner(
+                            bound,
+                            NonLifetimeBinderAllowed::Deny("trait object types"),
+                        );
                     }
                 });
                 match lifetime.res {
@@ -967,39 +1025,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
     }
 
     fn visit_poly_trait_ref(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) {
-        debug!("visit_poly_trait_ref(trait_ref={:?})", trait_ref);
-
-        let (mut binders, scope_type) = self.poly_trait_ref_binder_info();
-
-        let initial_bound_vars = binders.len() as u32;
-        let mut bound_vars: FxIndexMap<LocalDefId, ResolvedArg> = FxIndexMap::default();
-        let binders_iter =
-            trait_ref.bound_generic_params.iter().enumerate().map(|(late_bound_idx, param)| {
-                let pair = ResolvedArg::late(initial_bound_vars + late_bound_idx as u32, param);
-                let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
-                bound_vars.insert(pair.0, pair.1);
-                r
-            });
-        binders.extend(binders_iter);
-
-        debug!(?binders);
-        self.record_late_bound_vars(trait_ref.trait_ref.hir_ref_id, binders);
-
-        // Always introduce a scope here, even if this is in a where clause and
-        // we introduced the binders around the bounded Ty. In that case, we
-        // just reuse the concatenation functionality also present in nested trait
-        // refs.
-        let scope = Scope::Binder {
-            hir_id: trait_ref.trait_ref.hir_ref_id,
-            bound_vars,
-            s: self.scope,
-            scope_type,
-            where_bound_origin: None,
-        };
-        self.with(scope, |this| {
-            walk_list!(this, visit_generic_param, trait_ref.bound_generic_params);
-            this.visit_trait_ref(&trait_ref.trait_ref);
-        });
+        self.visit_poly_trait_ref_inner(trait_ref, NonLifetimeBinderAllowed::Allow);
     }
 }
 
@@ -1364,7 +1390,9 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             return;
         }
 
-        span_bug!(self.tcx.hir().span(hir_id), "could not resolve {param_def_id:?}",);
+        self.tcx
+            .sess
+            .delay_span_bug(self.tcx.hir().span(hir_id), "could not resolve {param_def_id:?}");
     }
 
     #[instrument(level = "debug", skip(self))]
@@ -1915,3 +1943,37 @@ fn is_late_bound_map(
         }
     }
 }
+
+pub fn deny_non_region_late_bound(
+    tcx: TyCtxt<'_>,
+    bound_vars: &mut FxIndexMap<LocalDefId, ResolvedArg>,
+    where_: &str,
+) {
+    let mut first = true;
+
+    for (var, arg) in bound_vars {
+        let Node::GenericParam(param) = tcx.hir().get_by_def_id(*var) else {
+            bug!();
+        };
+
+        let what = match param.kind {
+            hir::GenericParamKind::Type { .. } => "type",
+            hir::GenericParamKind::Const { .. } => "const",
+            hir::GenericParamKind::Lifetime { .. } => continue,
+        };
+
+        let mut diag = tcx.sess.struct_span_err(
+            param.span,
+            format!("late-bound {what} parameter not allowed on {where_}"),
+        );
+
+        let guar = if tcx.features().non_lifetime_binders && first {
+            diag.emit()
+        } else {
+            diag.delay_as_bug()
+        };
+
+        first = false;
+        *arg = ResolvedArg::Error(guar);
+    }
+}

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs

@@ -134,7 +134,8 @@ impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
                             rbv::ResolvedArg::StaticLifetime
                             | rbv::ResolvedArg::Free(_, _)
                             | rbv::ResolvedArg::EarlyBound(_)
-                            | rbv::ResolvedArg::LateBound(_, _, _),
+                            | rbv::ResolvedArg::LateBound(_, _, _)
+                            | rbv::ResolvedArg::Error(_),
                         )
                         | None,
                         _,
@@ -211,7 +212,8 @@ impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> {
                     rbv::ResolvedArg::StaticLifetime
                     | rbv::ResolvedArg::EarlyBound(_)
                     | rbv::ResolvedArg::LateBound(_, _, _)
-                    | rbv::ResolvedArg::Free(_, _),
+                    | rbv::ResolvedArg::Free(_, _)
+                    | rbv::ResolvedArg::Error(_),
                 )
                 | None,
                 _,

compiler/rustc_middle/src/middle/resolve_bound_vars.rs

@@ -3,6 +3,7 @@
 use crate::ty;
 
 use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{ItemLocalId, OwnerId};
 use rustc_macros::HashStable;
@@ -13,6 +14,7 @@ pub enum ResolvedArg {
     EarlyBound(/* decl */ DefId),
     LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* decl */ DefId),
     Free(DefId, /* lifetime decl */ DefId),
+    Error(ErrorGuaranteed),
 }
 
 /// A set containing, at most, one known element.

compiler/rustc_middle/src/ty/consts.rs

@@ -149,6 +149,9 @@ impl<'tcx> Const<'tcx> {
                         ty::ConstKind::Bound(debruijn, ty::BoundVar::from_u32(index)),
                         ty,
                     )),
+                    Some(rbv::ResolvedArg::Error(guar)) => {
+                        Some(tcx.const_error_with_guaranteed(ty, guar))
+                    }
                     arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", expr.hir_id),
                 }
             }

tests/ui/bounds-lifetime.stderr

@@ -22,7 +22,7 @@ error[E0658]: only lifetime parameters can be used in this context
 LL | type D = for<'a, T> fn();
    |                  ^
    |
-   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
    = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
 
 error[E0658]: only lifetime parameters can be used in this context
@@ -31,7 +31,7 @@ error[E0658]: only lifetime parameters can be used in this context
 LL | type E = dyn for<T> Fn();
    |                  ^
    |
-   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
    = help: add `#![feature(non_lifetime_binders)]` to the crate attributes to enable
 
 error: aborting due to 5 previous errors

tests/ui/closures/binder/const-bound.rs

@@ -0,0 +1,7 @@
+#![feature(closure_lifetime_binder, non_lifetime_binders)]
+//~^ WARN  is incomplete and may not be safe to use
+
+fn main()  {
+    for<const N: i32> || -> () {};
+    //~^ ERROR late-bound const parameter not allowed on closures
+}