Register even erroneous impls

Otherwise the specialization graph fails to pick it up, even though other code assumes that all impl blocks have an entry in the specialization graph.

compiler/rustc_middle/src/ty/fast_reject.rs

@@ -32,6 +32,7 @@ pub enum SimplifiedType {
     CoroutineWitness(DefId),
     Function(usize),
     Placeholder,
+    Error,
 }
 
 /// Generic parameters are pretty much just bound variables, e.g.
@@ -153,7 +154,8 @@ pub fn simplify_type<'tcx>(
             TreatParams::ForLookup | TreatParams::AsCandidateKey => None,
         },
         ty::Foreign(def_id) => Some(SimplifiedType::Foreign(def_id)),
-        ty::Bound(..) | ty::Infer(_) | ty::Error(_) => None,
+        ty::Error(_) => Some(SimplifiedType::Error),
+        ty::Bound(..) | ty::Infer(_) => None,
     }
 }
 

compiler/rustc_middle/src/ty/trait_def.rs

@@ -1,6 +1,5 @@
 use crate::traits::specialization_graph;
 use crate::ty::fast_reject::{self, SimplifiedType, TreatParams, TreatProjections};
-use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{Ident, Ty, TyCtxt};
 use hir::def_id::LOCAL_CRATE;
 use rustc_hir as hir;
@@ -241,9 +240,6 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
         let impl_def_id = impl_def_id.to_def_id();
 
         let impl_self_ty = tcx.type_of(impl_def_id).instantiate_identity();
-        if impl_self_ty.references_error() {
-            continue;
-        }
 
         if let Some(simplified_self_ty) =
             fast_reject::simplify_type(tcx, impl_self_ty, TreatParams::AsCandidateKey)

tests/ui/generic-associated-types/unknown-lifetime-ice-119827.rs

@@ -0,0 +1,16 @@
+trait Foo {
+    type Context<'c>
+    where
+        Self: 'c;
+}
+
+impl Foo for Box<dyn Foo> {}
+//~^ ERROR `Foo` cannot be made into an object
+//~| ERROR `Foo` cannot be made into an object
+//~| ERROR cycle detected
+//~| ERROR cycle detected
+//~| ERROR cycle detected
+//~| ERROR the trait bound `Box<(dyn Foo + 'static)>: Foo` is not satisfied
+//~| ERROR not all trait items implemented
+
+fn main() {}

tests/ui/generic-associated-types/unknown-lifetime-ice-119827.stderr

@@ -0,0 +1,119 @@
+error[E0391]: cycle detected when computing type of `<impl at $DIR/unknown-lifetime-ice-119827.rs:7:1: 7:26>`
+  --> $DIR/unknown-lifetime-ice-119827.rs:7:1
+   |
+LL | impl Foo for Box<dyn Foo> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: ...which requires finding trait impls of `Foo`...
+  --> $DIR/unknown-lifetime-ice-119827.rs:1:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
+   = note: ...which again requires computing type of `<impl at $DIR/unknown-lifetime-ice-119827.rs:7:1: 7:26>`, completing the cycle
+note: cycle used when collecting item types in top-level module
+  --> $DIR/unknown-lifetime-ice-119827.rs:1:1
+   |
+LL | / trait Foo {
+LL | |     type Context<'c>
+LL | |     where
+LL | |         Self: 'c;
+...  |
+LL | |
+LL | | fn main() {}
+   | |____________^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error[E0391]: cycle detected when computing type of `<impl at $DIR/unknown-lifetime-ice-119827.rs:7:1: 7:26>`
+  --> $DIR/unknown-lifetime-ice-119827.rs:7:1
+   |
+LL | impl Foo for Box<dyn Foo> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: ...which immediately requires computing type of `<impl at $DIR/unknown-lifetime-ice-119827.rs:7:1: 7:26>` again
+note: cycle used when collecting item types in top-level module
+  --> $DIR/unknown-lifetime-ice-119827.rs:1:1
+   |
+LL | / trait Foo {
+LL | |     type Context<'c>
+LL | |     where
+LL | |         Self: 'c;
+...  |
+LL | |
+LL | | fn main() {}
+   | |____________^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error[E0391]: cycle detected when computing type of `<impl at $DIR/unknown-lifetime-ice-119827.rs:7:1: 7:26>`
+  --> $DIR/unknown-lifetime-ice-119827.rs:7:1
+   |
+LL | impl Foo for Box<dyn Foo> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: ...which immediately requires computing type of `<impl at $DIR/unknown-lifetime-ice-119827.rs:7:1: 7:26>` again
+note: cycle used when collecting item types in top-level module
+  --> $DIR/unknown-lifetime-ice-119827.rs:1:1
+   |
+LL | / trait Foo {
+LL | |     type Context<'c>
+LL | |     where
+LL | |         Self: 'c;
+...  |
+LL | |
+LL | | fn main() {}
+   | |____________^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0038]: the trait `Foo` cannot be made into an object
+  --> $DIR/unknown-lifetime-ice-119827.rs:7:22
+   |
+LL | impl Foo for Box<dyn Foo> {}
+   |                      ^^^ `Foo` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/unknown-lifetime-ice-119827.rs:2:10
+   |
+LL | trait Foo {
+   |       --- this trait cannot be made into an object...
+LL |     type Context<'c>
+   |          ^^^^^^^ ...because it contains the generic associated type `Context`
+   = help: consider moving `Context` to another trait
+   = help: only type `{type error}` implements the trait, consider using it directly instead
+
+error[E0277]: the trait bound `Box<(dyn Foo + 'static)>: Foo` is not satisfied
+  --> $DIR/unknown-lifetime-ice-119827.rs:7:14
+   |
+LL | impl Foo for Box<dyn Foo> {}
+   |              ^^^^^^^^^^^^ the trait `Foo` is not implemented for `Box<(dyn Foo + 'static)>`
+   |
+   = help: the trait `Foo` is implemented for `Box<(dyn Foo + 'static)>`
+
+error[E0038]: the trait `Foo` cannot be made into an object
+  --> $DIR/unknown-lifetime-ice-119827.rs:7:14
+   |
+LL | impl Foo for Box<dyn Foo> {}
+   |              ^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/unknown-lifetime-ice-119827.rs:2:10
+   |
+LL | trait Foo {
+   |       --- this trait cannot be made into an object...
+LL |     type Context<'c>
+   |          ^^^^^^^ ...because it contains the generic associated type `Context`
+   = help: consider moving `Context` to another trait
+   = help: only type `std::boxed::Box<(dyn Foo + 'static)>` implements the trait, consider using it directly instead
+
+error[E0046]: not all trait items implemented, missing: `Context`
+  --> $DIR/unknown-lifetime-ice-119827.rs:7:1
+   |
+LL |     type Context<'c>
+   |     ---------------- `Context` from trait
+...
+LL | impl Foo for Box<dyn Foo> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ missing `Context` in implementation
+
+error: aborting due to 7 previous errors
+
+Some errors have detailed explanations: E0038, E0046, E0277, E0391.
+For more information about an error, try `rustc --explain E0038`.