fix ICE with references to infinite structs in consts

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1148,7 +1148,9 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                         // If returned by `struct_tail` this is the empty tuple.
                         | ty::Tuple(..)
                         // Integers and floats are always Sized, and so have unit type metadata.
-                        | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true,
+                        | ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..))
+                        // This happens if we reach the recursion limit when finding the struct tail.
+                        | ty::Error(..) => true,
 
                         // We normalize from `Wrapper<Tail>::Metadata` to `Tail::Metadata` if able.
                         // Otherwise, type parameters, opaques, and unnormalized projections have
@@ -1179,8 +1181,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                         | ty::Alias(..)
                         | ty::Bound(..)
                         | ty::Placeholder(..)
-                        | ty::Infer(..)
-                        | ty::Error(_) => {
+                        | ty::Infer(..) => {
                             if tail.has_infer_types() {
                                 candidate_set.mark_ambiguous();
                             }

tests/crashes/114484.rs → tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.rs

@@ -1,4 +1,12 @@
-//@ known-bug: #114484
+//@ build-fail
+
+//@ error-pattern: reached the recursion limit while instantiating
+//@ error-pattern: reached the recursion limit finding the struct tail
+
+// Regression test for #114484: This used to ICE during monomorphization, because we treated
+// `<VirtualWrapper<...> as Pointee>::Metadata` as a rigid projection after reaching the recursion
+// limit when finding the struct tail.
+
 use std::marker::PhantomData;
 
 trait MyTrait {

tests/ui/infinite/infinite-instantiation-struct-tail-ice-114484.stderr

@@ -0,0 +1,86 @@
+error: reached the recursion limit finding the struct tail for `[u8; 256]`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+
+error: reached the recursion limit finding the struct tail for `[u8; 256]`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: reached the recursion limit finding the struct tail for `[u8; 256]`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: reached the recursion limit finding the struct tail for `[u8; 256]`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+note: the above error was encountered while instantiating `fn virtualize_my_trait::<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<SomeData<256>, 0>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>>`
+  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:26:18
+   |
+LL |         unsafe { virtualize_my_trait(L, self) }
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: reached the recursion limit finding the struct tail for `SomeData<256>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+
+error: reached the recursion limit finding the struct tail for `SomeData<256>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: reached the recursion limit finding the struct tail for `SomeData<256>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: reached the recursion limit finding the struct tail for `SomeData<256>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+note: the above error was encountered while instantiating `fn virtualize_my_trait::<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<SomeData<256>, 0>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>>`
+  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:26:18
+   |
+LL |         unsafe { virtualize_my_trait(L, self) }
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+
+error: reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: reached the recursion limit finding the struct tail for `VirtualWrapper<SomeData<256>, 0>`
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+note: the above error was encountered while instantiating `fn virtualize_my_trait::<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<SomeData<256>, 0>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>, 1>>`
+  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:26:18
+   |
+LL |         unsafe { virtualize_my_trait(L, self) }
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: reached the recursion limit while instantiating `<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<VirtualWrapper<..., 1>, 1>, 1>, 1>, 1> as MyTrait>::virtualize`
+   |
+note: `<VirtualWrapper<T, L> as MyTrait>::virtualize` defined here
+  --> $DIR/infinite-instantiation-struct-tail-ice-114484.rs:25:5
+   |
+LL |     fn virtualize(&self) -> &dyn MyTrait {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: the full type name has been written to '$TEST_BUILD_DIR/infinite/infinite-instantiation-struct-tail-ice-114484/infinite-instantiation-struct-tail-ice-114484.long-type.txt'
+
+error: aborting due to 13 previous errors
+

tests/ui/structs/ice-struct-tail-normalization-113272.rs

@@ -13,5 +13,6 @@ struct Other {
 fn main() {
     unsafe {
         std::mem::transmute::<Option<()>, Option<&Other>>(None);
+        //~^ ERROR cannot transmute
     }
 }

tests/ui/structs/ice-struct-tail-normalization-113272.stderr

@@ -13,7 +13,16 @@ LL |     type RefTarget;
 LL | impl Trait for () where Missing: Trait {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `RefTarget` in implementation
 
-error: aborting due to 2 previous errors
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> $DIR/ice-struct-tail-normalization-113272.rs:15:9
+   |
+LL |         std::mem::transmute::<Option<()>, Option<&Other>>(None);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: source type: `Option<()>` (8 bits)
+   = note: target type: `Option<&Other>` (unable to determine layout for `Other` because `<() as Trait>::RefTarget` cannot be normalized)
+
+error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0046, E0412.
+Some errors have detailed explanations: E0046, E0412, E0512.
 For more information about an error, try `rustc --explain E0046`.