Auto merge of #125671 - BoxyUwU:remove_const_ty_eq, r=compiler-errors

Do not equate `Const`'s ty in `super_combine_const`

Fixes #114456

In #125451 we started relating the `Const`'s tys outside of a probe so it was no longer simply an assertion to catch bugs.

This was done so that when we _do_ provide a wrongly typed const argument to an item if we wind up relating it with some other instantiation we'll have a `TypeError` we can bubble up and taint the resulting mir allowing const eval to skip evaluation.

In this PR I instead change `ConstArgHasType` to correctly handle checking the types of const inference variables. Previously if we had something like `impl<const N: u32> Trait for [(); N]`, when using the impl we would instantiate it with infer vars and then check that `?x: u32` is of type `u32` and succeed. Then later we would infer `?x` to some `Const` of type `usize`.

We now stall on `?x` in `ConstArgHasType` until it has a concrete value that we can determine the type of. This allows us to fail using the erroneous implementation of `Trait` which allows us to taint the mir.

Long term we intend to remove the `ty` field on `Const` so we would have no way of accessing the `ty` of a const inference variable anyway and would have to do this. I did not fully update `ConstArgHasType` to avoid using the `ty` field as it's not entirely possible right now- we would need to lookup `ConstArgHasType` candidates in the env.

---

As for _why_ I think we should do this, relating the types of const's is not necessary for soundness of the type system. Originally this check started off as a plain `==` in `super_relate_consts` and gradually has been growing in complexity as we support more complicated types. It was never actually required to ensure that const arguments are correctly typed for their parameters however.

The way we currently check that a const argument has the correct type is a little convoluted and confusing (and will hopefully be less weird as time goes on). Every const argument has an anon const with its return type set to type of the const parameter it is an argument to. When type checking the anon const regular type checking rules require that the expression is the same type as the return type. This effectively ensure that no matter what every const argument _always_ has the correct type.

An extra bit of complexity is that during `hir_ty_lowering` we do not represent everything as a `ConstKind::Unevaluated` corresponding to the anon const. For generic parameters i.e. `[(); N]` we simply represent them as `ConstKind::Param` as we do not want `ConstKind::Unevaluated` with generic substs on stable under min const generics. The anon const still gets type checked resulting in errors about type mismatches.

Eventually we intend to not create anon consts for all const arguments (for example for `ConstKind::Param`) and instead check that the argument type is correct via `ConstArgHasType` obligations (these effectively also act as a check that the anon consts have the correctly set return type).

What this all means is that the the only time we should ever have mismatched types when relating two `Const`s is if we have messed up our logic for ensuring that const arguments are of the correct type. Having this not be an assert is:
- Confusing as it may incorrectly lead people to believe this is an important check that is actually required
- Opens the possibility for bugs or behaviour reliant on this (unnecessary) check existing

---

This PR makes two tests go from pass->ICE (`generic_const_exprs/ice-125520-layout-mismatch-mulwithoverflow.rs` and `tests/crashes/121858.rs`). This is caused by the fact that we evaluate anon consts even if their where clauses do not hold and is a pre-existing issue and only affects `generic_const_exprs`. I am comfortable exposing the brokenness of `generic_const_exprs` more with this PR

This PR makes a test go from ICE->pass (`const-generics/issues/issue-105821.rs`). I have no idea why this PR affects that but I believe that ICE is an unrelated issue to do with the fact that under `generic_const_exprs`/`adt_const_params` we do not handle lifetimes in const parameter types correctly. This PR is likely just masking this bug.

Note: this PR doesn't re-introduce the assertion that the two consts' tys are equal. I'm not really sure how I feel about this but tbh it has caused more ICEs than its found lately so :woman_shrugging:

r? `@oli-obk` `@compiler-errors`

30 files changed, 206 insertions, 327 deletions

diff --git a/compiler/rustc_infer/src/infer/relate/combine.rs b/compiler/rustc_infer/src/infer/relate/combine.rs
index 6b41e450684..04ca043e6fe 100644
--- a/compiler/rustc_infer/src/infer/relate/combine.rs
+++ b/compiler/rustc_infer/src/infer/relate/combine.rs
@@ -22,11 +22,10 @@ use super::glb::Glb;
 use super::lub::Lub;
 use super::type_relating::TypeRelating;
 use super::StructurallyRelateAliases;
-use crate::infer::{DefineOpaqueTypes, InferCtxt, InferOk, TypeTrace};
+use crate::infer::{DefineOpaqueTypes, InferCtxt, TypeTrace};
 use crate::traits::{Obligation, PredicateObligations};
 use rustc_middle::bug;
 use rustc_middle::infer::unify_key::EffectVarValue;
-use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::relate::{RelateResult, TypeRelation};
 use rustc_middle::ty::{self, InferConst, Ty, TyCtxt, TypeVisitableExt, Upcast};
@@ -170,12 +169,6 @@ impl<'tcx> InferCtxt<'tcx> {
         let a = self.shallow_resolve_const(a);
         let b = self.shallow_resolve_const(b);
 
-        // It is always an error if the types of two constants that are related are not equal.
-        let InferOk { value: (), obligations } = self
-            .at(&ObligationCause::dummy_with_span(relation.span()), relation.param_env())
-            .eq(DefineOpaqueTypes::No, a.ty(), b.ty())?;
-        relation.register_obligations(obligations);
-
         match (a.kind(), b.kind()) {
             (
                 ty::ConstKind::Infer(InferConst::Var(a_vid)),
diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs
index a432090f78c..f9febd290fe 100644
--- a/compiler/rustc_trait_selection/src/solve/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/mod.rs
@@ -197,8 +197,30 @@ impl<'a, 'tcx> EvalCtxt<'a, InferCtxt<'tcx>> {
         goal: Goal<'tcx, (ty::Const<'tcx>, Ty<'tcx>)>,
     ) -> QueryResult<'tcx> {
         let (ct, ty) = goal.predicate;
-        self.eq(goal.param_env, ct.ty(), ty)?;
-        self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+
+        // FIXME(BoxyUwU): Really we should not be calling `ct.ty()` for any variant
+        // other than `ConstKind::Value`. Unfortunately this would require looking in the
+        // env for any `ConstArgHasType` assumptions for parameters and placeholders. I
+        // have not yet gotten around to implementing this though.
+        //
+        // We do still stall on infer vars though as otherwise a goal like:
+        // `ConstArgHasType(?x: usize, usize)` can succeed even though it might later
+        // get unified with some const that is not of type `usize`.
+        match ct.kind() {
+            // FIXME: Ignore effect vars because canonicalization doesn't handle them correctly
+            // and if we stall on the var then we wind up creating ambiguity errors in a probe
+            // for this goal which contains an effect var. Which then ends up ICEing.
+            ty::ConstKind::Infer(ty::InferConst::Var(_)) => {
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
+            }
+            ty::ConstKind::Error(_) => {
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+            }
+            _ => {
+                self.eq(goal.param_env, ct.ty(), ty)?;
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+            }
+        }
     }
 }
 
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index 46953a61296..7f995b315f7 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -2685,6 +2685,22 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     .with_span_label(span, format!("cannot satisfy `{predicate}`"))
                 }
             }
+
+            // Given some `ConstArgHasType(?x, usize)`, we should not emit an error such as
+            // "type annotations needed: cannot satisfy the constant `_` has type `usize`"
+            // Instead we should emit a normal error suggesting the user to turbofish the
+            // const parameter that is currently being inferred. Unfortunately we cannot
+            // nicely emit such an error so we delay an ICE incase nobody else reports it
+            // for us.
+            ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
+                return self.tcx.sess.dcx().span_delayed_bug(
+                    span,
+                    format!(
+                        "`ambiguous ConstArgHasType({:?}, {:?}) unaccompanied by inference error`",
+                        ct, ty
+                    ),
+                );
+            }
             _ => {
                 if let Some(e) = self.tainted_by_errors() {
                     return e;
diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
index 629f6f394af..e1afc2a3529 100644
--- a/compiler/rustc_trait_selection/src/traits/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -429,16 +429,37 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
                 // This is because this is not ever a useful obligation to report
                 // as the cause of an overflow.
                 ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
-                    match self.selcx.infcx.at(&obligation.cause, obligation.param_env).eq(
-                        // Only really excercised by generic_const_exprs
-                        DefineOpaqueTypes::Yes,
-                        ct.ty(),
-                        ty,
-                    ) {
-                        Ok(inf_ok) => ProcessResult::Changed(mk_pending(inf_ok.into_obligations())),
-                        Err(_) => ProcessResult::Error(FulfillmentErrorCode::Select(
-                            SelectionError::Unimplemented,
-                        )),
+                    // FIXME(BoxyUwU): Really we should not be calling `ct.ty()` for any variant
+                    // other than `ConstKind::Value`. Unfortunately this would require looking in the
+                    // env for any `ConstArgHasType` assumptions for parameters and placeholders. I
+                    // don't really want to implement this in the old solver so I haven't.
+                    //
+                    // We do still stall on infer vars though as otherwise a goal like:
+                    // `ConstArgHasType(?x: usize, usize)` can succeed even though it might later
+                    // get unified with some const that is not of type `usize`.
+                    let ct = self.selcx.infcx.shallow_resolve_const(ct);
+                    match ct.kind() {
+                        ty::ConstKind::Infer(ty::InferConst::Var(vid)) => {
+                            pending_obligation.stalled_on.clear();
+                            pending_obligation.stalled_on.extend([TyOrConstInferVar::Const(vid)]);
+                            ProcessResult::Unchanged
+                        }
+                        ty::ConstKind::Error(_) => return ProcessResult::Changed(vec![]),
+                        _ => {
+                            match self.selcx.infcx.at(&obligation.cause, obligation.param_env).eq(
+                                // Only really excercised by generic_const_exprs
+                                DefineOpaqueTypes::Yes,
+                                ct.ty(),
+                                ty,
+                            ) {
+                                Ok(inf_ok) => {
+                                    ProcessResult::Changed(mk_pending(inf_ok.into_obligations()))
+                                }
+                                Err(_) => ProcessResult::Error(FulfillmentErrorCode::Select(
+                                    SelectionError::Unimplemented,
+                                )),
+                            }
+                        }
                     }
                 }
 
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 7aec4e1987e..92c0c37d0c3 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -995,10 +995,27 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 }
                 ty::PredicateKind::Ambiguous => Ok(EvaluatedToAmbig),
                 ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
+                    // FIXME(BoxyUwU): Really we should not be calling `ct.ty()` for any variant
+                    // other than `ConstKind::Value`. Unfortunately this would require looking in the
+                    // env for any `ConstArgHasType` assumptions for parameters and placeholders. I
+                    // don't really want to implement this in the old solver so I haven't.
+                    //
+                    // We do still stall on infer vars though as otherwise a goal like:
+                    // `ConstArgHasType(?x: usize, usize)` can succeed even though it might later
+                    // get unified with some const that is not of type `usize`.
+                    let ct = self.infcx.shallow_resolve_const(ct);
+                    let ct_ty = match ct.kind() {
+                        ty::ConstKind::Infer(ty::InferConst::Var(_)) => {
+                            return Ok(EvaluatedToAmbig);
+                        }
+                        ty::ConstKind::Error(_) => return Ok(EvaluatedToOk),
+                        _ => ct.ty(),
+                    };
+
                     match self.infcx.at(&obligation.cause, obligation.param_env).eq(
                         // Only really excercised by generic_const_exprs
                         DefineOpaqueTypes::Yes,
-                        ct.ty(),
+                        ct_ty,
                         ty,
                     ) {
                         Ok(inf_ok) => self.evaluate_predicates_recursively(
diff --git a/tests/ui/consts/eval_type_mismatch.rs b/tests/crashes/121858.rs
index 3d821ab538e..7d5bae37f84 100644
--- a/tests/ui/consts/eval_type_mismatch.rs
+++ b/tests/crashes/121858.rs
@@ -1,17 +1,14 @@
+//@ known-bug: #121858
 #![feature(generic_const_exprs)]
-#![allow(incomplete_features)]
 
 struct Outer<const A: i64, const B: usize>();
 impl<const A: usize, const B: usize> Outer<A, B>
-//~^ ERROR: `A` is not of type `i64`
-//~| ERROR: mismatched types
 where
     [(); A + (B * 2)]:,
 {
-    fn o() {}
+    fn o() -> Union {}
 }
 
 fn main() {
     Outer::<1, 1>::o();
-    //~^ ERROR: no function or associated item named `o` found
 }
diff --git a/tests/crashes/122638.rs b/tests/crashes/122638.rs
deleted file mode 100644
index af0fc5bbd50..00000000000
--- a/tests/crashes/122638.rs
+++ /dev/null
@@ -1,12 +0,0 @@
-//@ known-bug: #122638
-#![feature(min_specialization)]
-
-impl<'a, T: std::fmt::Debug, const N: usize> Iterator for ConstChunksExact<'a, T, { N }> {
-    fn next(&mut self) -> Option<Self::Item> {}
-}
-
-struct ConstChunksExact<'a, T: '_, const assert: usize> {}
-
-impl<'a, T: std::fmt::Debug, const N: usize> Iterator for ConstChunksExact<'a, T, {}> {
-    type Item = &'a [T; N];
-}
diff --git a/tests/crashes/123141-2.rs b/tests/crashes/123141-2.rs
deleted file mode 100644
index 74f961c2a33..00000000000
--- a/tests/crashes/123141-2.rs
+++ /dev/null
@@ -1,23 +0,0 @@
-//@ known-bug: #123141
-
-trait ConstChunksExactTrait<T> {
-    fn const_chunks_exact<const N: usize>(&self) -> ConstChunksExact<'_, T, {N}>;
-}
-
-impl <T> ConstChunksExactTrait<T> for [T] {}
-
-struct ConstChunksExact<'a, T: 'a, const N: usize> {}
-
-impl <'a, T: , const N: usize> Iterator for ConstChunksExact<'a, T, {rem}> {
-    type Item = &'a [T; N];
-}
-
-fn main() {
-    let slice = &[1i32, 2, 3, 4, 5, 6, 7, 7, 9, 1i32];
-
-    let mut iter = [[1, 2, 3], [4, 5, 6], [7, 8 ,9]].iter();
-
-    for a in slice.const_chunks_exact::<3>() {
-        assert_eq!(a, iter.next().unwrap());
-    }
-}
diff --git a/tests/crashes/123141.rs b/tests/crashes/123141.rs
index 99dfee7670e..07181387e04 100644
--- a/tests/crashes/123141.rs
+++ b/tests/crashes/123141.rs
@@ -1,22 +1,23 @@
 //@ known-bug: #123141
-trait ConstChunksExactTrait<T> {
-    fn const_chunks_exact<const N: usize>(&self) -> ConstChunksExact<'_, T, { N }>;
+
+trait Trait {
+    fn next(self) -> Self::Item;
+    type Item;
 }
 
-impl<T> ConstChunksExactTrait<T> for [T] {}
+struct Foo<T: ?Sized>(T);
 
-struct ConstChunksExact<'a, T: 'a, const N: usize> {}
+impl<T: ?Sized, U> Trait for Foo<U> {
+    type Item = Foo<T>;
+    fn next(self) -> Self::Item {
+        loop {}
+    }
+}
 
-impl<'a, T, const N: usize> Iterator for ConstChunksExact<'a, T, { rem }> {
-    type Item = &'a [T; N];
+fn opaque() -> impl Trait {
+    Foo::<_>(10_u32)
 }
 
 fn main() {
-    let slice = &[1i32, 2, 3, 4, 5, 6, 7, 7, 9, 1i32];
-
-    let mut iter = [[1, 2, 3], [4, 5, 6], [7, 8, 9]].iter();
-
-    for a in slice.const_chunks_exact::<3>() {
-        assert_eq!(a, iter.next().unwrap());
-    }
+    opaque().next();
 }
diff --git a/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.rs b/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.rs
index 89d0b74d403..fa0b0fdc136 100644
--- a/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.rs
+++ b/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.rs
@@ -8,5 +8,6 @@ impl<const N: u8> Trait for [(); N] {}
 //~^ ERROR: mismatched types
 impl<const N: i8> Trait for [(); N] {}
 //~^ ERROR: mismatched types
+//~| ERROR: conflicting implementations of trait `Trait`
 
 fn main() {}
diff --git a/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.stderr b/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.stderr
index d1950254660..d65450845bc 100644
--- a/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.stderr
+++ b/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.stderr
@@ -1,3 +1,12 @@
+error[E0119]: conflicting implementations of trait `Trait` for type `[(); _]`
+  --> $DIR/generic_const_type_mismatch.rs:9:1
+   |
+LL | impl<const N: u8> Trait for [(); N] {}
+   | ----------------------------------- first implementation here
+LL |
+LL | impl<const N: i8> Trait for [(); N] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `[(); _]`
+
 error[E0308]: mismatched types
   --> $DIR/generic_const_type_mismatch.rs:7:34
    |
@@ -10,6 +19,7 @@ error[E0308]: mismatched types
 LL | impl<const N: i8> Trait for [(); N] {}
    |                                  ^ expected `usize`, found `i8`
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0119, E0308.
+For more information about an error, try `rustc --explain E0119`.
diff --git a/tests/crashes/114456.rs b/tests/ui/const-generics/adt_const_params/alias_const_param_ty-1.rs
index e347327e738..8035fce0914 100644
--- a/tests/crashes/114456.rs
+++ b/tests/ui/const-generics/adt_const_params/alias_const_param_ty-1.rs
@@ -1,5 +1,7 @@
-//@ known-bug: #114456
+//@ check-pass
 #![feature(adt_const_params, lazy_type_alias)]
+//~^ WARN: the feature `adt_const_params` is incomplete
+//~| WARN: the feature `lazy_type_alias` is incomplete
 
 pub type Matrix = [usize; 1];
 const EMPTY_MATRIX: Matrix = [0; 1];
diff --git a/tests/ui/const-generics/adt_const_params/alias_const_param_ty-1.stderr b/tests/ui/const-generics/adt_const_params/alias_const_param_ty-1.stderr
new file mode 100644
index 00000000000..5c6981077b2
--- /dev/null
+++ b/tests/ui/const-generics/adt_const_params/alias_const_param_ty-1.stderr
@@ -0,0 +1,19 @@
+warning: the feature `adt_const_params` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/alias_const_param_ty-1.rs:2:12
+   |
+LL | #![feature(adt_const_params, lazy_type_alias)]
+   |            ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #95174 <https://github.com/rust-lang/rust/issues/95174> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: the feature `lazy_type_alias` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/alias_const_param_ty-1.rs:2:30
+   |
+LL | #![feature(adt_const_params, lazy_type_alias)]
+   |                              ^^^^^^^^^^^^^^^
+   |
+   = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
+
+warning: 2 warnings emitted
+
diff --git a/tests/crashes/114456-2.rs b/tests/ui/const-generics/adt_const_params/alias_const_param_ty-2.rs
index eca27febb96..a576b75341c 100644
--- a/tests/crashes/114456-2.rs
+++ b/tests/ui/const-generics/adt_const_params/alias_const_param_ty-2.rs
@@ -1,5 +1,6 @@
-//@ known-bug: #114456
+//@ check-pass
 #![feature(adt_const_params)]
+//~^ WARN: the feature `adt_const_params` is incomplete
 
 const EMPTY_MATRIX: <Type as Trait>::Matrix = [0; 1];
 
@@ -12,8 +13,12 @@ impl Walk<EMPTY_MATRIX> {
 }
 
 pub enum Type {}
-pub trait Trait { type Matrix; }
-impl Trait for Type { type Matrix = [usize; 1]; }
+pub trait Trait {
+    type Matrix;
+}
+impl Trait for Type {
+    type Matrix = [usize; 1];
+}
 
 fn main() {
     let _ = Walk::new();
diff --git a/tests/ui/const-generics/adt_const_params/alias_const_param_ty-2.stderr b/tests/ui/const-generics/adt_const_params/alias_const_param_ty-2.stderr
new file mode 100644
index 00000000000..dbc8ab71636
--- /dev/null
+++ b/tests/ui/const-generics/adt_const_params/alias_const_param_ty-2.stderr
@@ -0,0 +1,11 @@
+warning: the feature `adt_const_params` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/alias_const_param_ty-2.rs:2:12
+   |
+LL | #![feature(adt_const_params)]
+   |            ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #95174 <https://github.com/rust-lang/rust/issues/95174> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/tests/ui/const-generics/bad-subst-const-kind.rs b/tests/ui/const-generics/bad-subst-const-kind.rs
index 88f98a54b6e..d5913879191 100644
--- a/tests/ui/const-generics/bad-subst-const-kind.rs
+++ b/tests/ui/const-generics/bad-subst-const-kind.rs
@@ -10,5 +10,7 @@ impl<const N: u64> Q for [u8; N] {
     const ASSOC: usize = 1;
 }
 
-pub fn test() -> [u8; <[u8; 13] as Q>::ASSOC] { todo!() }
-//~^ ERROR: `[u8; 13]: Q` is not satisfied
+pub fn test() -> [u8; <[u8; 13] as Q>::ASSOC] {
+    //~^ ERROR: the constant `13` is not of type `u64`
+    todo!()
+}
diff --git a/tests/ui/const-generics/bad-subst-const-kind.stderr b/tests/ui/const-generics/bad-subst-const-kind.stderr
index 6cf9fa743b3..6725f6762e4 100644
--- a/tests/ui/const-generics/bad-subst-const-kind.stderr
+++ b/tests/ui/const-generics/bad-subst-const-kind.stderr
@@ -1,10 +1,16 @@
-error[E0277]: the trait bound `[u8; 13]: Q` is not satisfied
+error: the constant `13` is not of type `u64`
   --> $DIR/bad-subst-const-kind.rs:13:24
    |
-LL | pub fn test() -> [u8; <[u8; 13] as Q>::ASSOC] { todo!() }
-   |                        ^^^^^^^^ the trait `Q` is not implemented for `[u8; 13]`
+LL | pub fn test() -> [u8; <[u8; 13] as Q>::ASSOC] {
+   |                        ^^^^^^^^ expected `u64`, found `usize`
    |
-   = help: the trait `Q` is implemented for `[u8; N]`
+note: required for `[u8; 13]` to implement `Q`
+  --> $DIR/bad-subst-const-kind.rs:8:20
+   |
+LL | impl<const N: u64> Q for [u8; N] {
+   |      ------------  ^     ^^^^^^^
+   |      |
+   |      unsatisfied trait bound introduced here
 
 error[E0308]: mismatched types
   --> $DIR/bad-subst-const-kind.rs:8:31
@@ -14,5 +20,4 @@ LL | impl<const N: u64> Q for [u8; N] {
 
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0277, E0308.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/const-generics/defaults/doesnt_infer.rs b/tests/ui/const-generics/defaults/doesnt_infer.rs
index e14c08fc148..016685eee9d 100644
--- a/tests/ui/const-generics/defaults/doesnt_infer.rs
+++ b/tests/ui/const-generics/defaults/doesnt_infer.rs
@@ -3,7 +3,9 @@
 struct Foo<const N: u32 = 2>;
 
 impl<const N: u32> Foo<N> {
-    fn foo() -> Self { loop {} }
+    fn foo() -> Self {
+        loop {}
+    }
 }
 
 fn main() {
diff --git a/tests/ui/const-generics/defaults/doesnt_infer.stderr b/tests/ui/const-generics/defaults/doesnt_infer.stderr
index 93d58603397..1e779f75ce0 100644
--- a/tests/ui/const-generics/defaults/doesnt_infer.stderr
+++ b/tests/ui/const-generics/defaults/doesnt_infer.stderr
@@ -1,5 +1,5 @@
 error[E0282]: type annotations needed for `Foo<_>`
-  --> $DIR/doesnt_infer.rs:11:9
+  --> $DIR/doesnt_infer.rs:13:9
    |
 LL |     let foo = Foo::foo();
    |         ^^^
diff --git a/tests/ui/const-generics/generic_arg_infer/issue-91614.rs b/tests/ui/const-generics/generic_arg_infer/issue-91614.rs
index b45e2cbc737..cfbc5faecd9 100644
--- a/tests/ui/const-generics/generic_arg_infer/issue-91614.rs
+++ b/tests/ui/const-generics/generic_arg_infer/issue-91614.rs
@@ -4,5 +4,5 @@ use std::simd::Mask;
 
 fn main() {
     let y = Mask::<_, _>::splat(false);
-    //~^ ERROR: type annotations needed for
+    //~^ ERROR: type annotations needed
 }
diff --git a/tests/ui/const-generics/generic_const_exprs/ice-125520-layout-mismatch-mulwithoverflow.rs b/tests/ui/const-generics/generic_const_exprs/ice-125520-layout-mismatch-mulwithoverflow.rs
deleted file mode 100644
index cd2dc3f4fe8..00000000000
--- a/tests/ui/const-generics/generic_const_exprs/ice-125520-layout-mismatch-mulwithoverflow.rs
+++ /dev/null
@@ -1,27 +0,0 @@
-// issue: rust-lang/rust#125520
-#![feature(generic_const_exprs)]
-//~^ WARN the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
-
-struct Outer<const A: i64, const B: i64>();
-impl<const A: usize, const B: usize> Outer<A, B>
-//~^ ERROR the constant `A` is not of type `i64`
-//~| ERROR the constant `B` is not of type `i64`
-//~| ERROR mismatched types
-//~| ERROR mismatched types
-where
-    [(); A + (B * 2)]:,
-{
-    fn i() -> Self {
-    //~^ ERROR the constant `A` is not of type `i64`
-    //~| ERROR the constant `B` is not of type `i64`
-        Self
-        //~^ ERROR mismatched types
-        //~| ERROR the constant `A` is not of type `i64`
-        //~| ERROR the constant `B` is not of type `i64`
-    }
-}
-
-fn main() {
-    Outer::<1, 1>::o();
-    //~^ ERROR no function or associated item named `o` found for struct `Outer` in the current scope
-}
diff --git a/tests/ui/const-generics/generic_const_exprs/ice-125520-layout-mismatch-mulwithoverflow.stderr b/tests/ui/const-generics/generic_const_exprs/ice-125520-layout-mismatch-mulwithoverflow.stderr
deleted file mode 100644
index 2dbd69fd3bc..00000000000
--- a/tests/ui/const-generics/generic_const_exprs/ice-125520-layout-mismatch-mulwithoverflow.stderr
+++ /dev/null
@@ -1,125 +0,0 @@
-warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:2:12
-   |
-LL | #![feature(generic_const_exprs)]
-   |            ^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-error: the constant `A` is not of type `i64`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:6:38
-   |
-LL | impl<const A: usize, const B: usize> Outer<A, B>
-   |                                      ^^^^^^^^^^^ expected `i64`, found `usize`
-   |
-note: required by a bound in `Outer`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:5:14
-   |
-LL | struct Outer<const A: i64, const B: i64>();
-   |              ^^^^^^^^^^^^ required by this bound in `Outer`
-
-error: the constant `B` is not of type `i64`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:6:38
-   |
-LL | impl<const A: usize, const B: usize> Outer<A, B>
-   |                                      ^^^^^^^^^^^ expected `i64`, found `usize`
-   |
-note: required by a bound in `Outer`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:5:28
-   |
-LL | struct Outer<const A: i64, const B: i64>();
-   |                            ^^^^^^^^^^^^ required by this bound in `Outer`
-
-error: the constant `A` is not of type `i64`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:14:15
-   |
-LL |     fn i() -> Self {
-   |               ^^^^ expected `i64`, found `usize`
-   |
-note: required by a bound in `Outer`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:5:14
-   |
-LL | struct Outer<const A: i64, const B: i64>();
-   |              ^^^^^^^^^^^^ required by this bound in `Outer`
-
-error: the constant `B` is not of type `i64`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:14:15
-   |
-LL |     fn i() -> Self {
-   |               ^^^^ expected `i64`, found `usize`
-   |
-note: required by a bound in `Outer`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:5:28
-   |
-LL | struct Outer<const A: i64, const B: i64>();
-   |                            ^^^^^^^^^^^^ required by this bound in `Outer`
-
-error[E0308]: mismatched types
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:17:9
-   |
-LL | struct Outer<const A: i64, const B: i64>();
-   | ---------------------------------------- `Outer` defines a struct constructor here, which should be called
-...
-LL |     fn i() -> Self {
-   |               ---- expected `Outer<A, B>` because of return type
-...
-LL |         Self
-   |         ^^^^ expected `Outer<A, B>`, found struct constructor
-   |
-   = note:          expected struct `Outer<A, B>`
-           found struct constructor `fn() -> Outer<A, B> {Outer::<A, B>}`
-help: use parentheses to construct this tuple struct
-   |
-LL |         Self()
-   |             ++
-
-error: the constant `A` is not of type `i64`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:17:9
-   |
-LL |         Self
-   |         ^^^^ expected `i64`, found `usize`
-   |
-note: required by a bound in `Outer`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:5:14
-   |
-LL | struct Outer<const A: i64, const B: i64>();
-   |              ^^^^^^^^^^^^ required by this bound in `Outer`
-
-error: the constant `B` is not of type `i64`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:17:9
-   |
-LL |         Self
-   |         ^^^^ expected `i64`, found `usize`
-   |
-note: required by a bound in `Outer`
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:5:28
-   |
-LL | struct Outer<const A: i64, const B: i64>();
-   |                            ^^^^^^^^^^^^ required by this bound in `Outer`
-
-error[E0599]: no function or associated item named `o` found for struct `Outer` in the current scope
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:25:20
-   |
-LL | struct Outer<const A: i64, const B: i64>();
-   | ---------------------------------------- function or associated item `o` not found for this struct
-...
-LL |     Outer::<1, 1>::o();
-   |                    ^ function or associated item not found in `Outer<1, 1>`
-
-error[E0308]: mismatched types
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:6:44
-   |
-LL | impl<const A: usize, const B: usize> Outer<A, B>
-   |                                            ^ expected `i64`, found `usize`
-
-error[E0308]: mismatched types
-  --> $DIR/ice-125520-layout-mismatch-mulwithoverflow.rs:6:47
-   |
-LL | impl<const A: usize, const B: usize> Outer<A, B>
-   |                                               ^ expected `i64`, found `usize`
-
-error: aborting due to 10 previous errors; 1 warning emitted
-
-Some errors have detailed explanations: E0308, E0599.
-For more information about an error, try `rustc --explain E0308`.
diff --git a/tests/ui/const-generics/generic_const_exprs/type_mismatch.rs b/tests/ui/const-generics/generic_const_exprs/type_mismatch.rs
index 285f9dee6c2..6b0d9e047db 100644
--- a/tests/ui/const-generics/generic_const_exprs/type_mismatch.rs
+++ b/tests/ui/const-generics/generic_const_exprs/type_mismatch.rs
@@ -10,7 +10,7 @@ impl<const N: u64> Q for [u8; N] {}
 //~| ERROR mismatched types
 
 pub fn q_user() -> [u8; <[u8; 13] as Q>::ASSOC] {}
-//~^ ERROR `[u8; 13]: Q` is not satisfied
+//~^ ERROR the constant `13` is not of type `u64`
 //~| ERROR mismatched types
 
 pub fn main() {}
diff --git a/tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr b/tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr
index a63a56dd675..bb6d650b7ab 100644
--- a/tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr
+++ b/tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr
@@ -7,13 +7,19 @@ LL |     const ASSOC: usize;
 LL | impl<const N: u64> Q for [u8; N] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `ASSOC` in implementation
 
-error[E0277]: the trait bound `[u8; 13]: Q` is not satisfied
+error: the constant `13` is not of type `u64`
   --> $DIR/type_mismatch.rs:12:26
    |
 LL | pub fn q_user() -> [u8; <[u8; 13] as Q>::ASSOC] {}
-   |                          ^^^^^^^^ the trait `Q` is not implemented for `[u8; 13]`
+   |                          ^^^^^^^^ expected `u64`, found `usize`
    |
-   = help: the trait `Q` is implemented for `[u8; N]`
+note: required for `[u8; 13]` to implement `Q`
+  --> $DIR/type_mismatch.rs:8:20
+   |
+LL | impl<const N: u64> Q for [u8; N] {}
+   |      ------------  ^     ^^^^^^^
+   |      |
+   |      unsatisfied trait bound introduced here
 
 error[E0308]: mismatched types
   --> $DIR/type_mismatch.rs:12:20
@@ -31,5 +37,5 @@ LL | impl<const N: u64> Q for [u8; N] {}
 
 error: aborting due to 4 previous errors
 
-Some errors have detailed explanations: E0046, E0277, E0308.
+Some errors have detailed explanations: E0046, E0308.
 For more information about an error, try `rustc --explain E0046`.
diff --git a/tests/ui/const-generics/issues/issue-105821.rs b/tests/ui/const-generics/issues/issue-105821.rs
index e55da461605..ecbae4d9f35 100644
--- a/tests/ui/const-generics/issues/issue-105821.rs
+++ b/tests/ui/const-generics/issues/issue-105821.rs
@@ -1,10 +1,7 @@
-//@ failure-status: 101
-//@ known-bug: rust-lang/rust#125451
-//@ normalize-stderr-test "note: .*\n\n" -> ""
-//@ normalize-stderr-test "thread 'rustc' panicked.*\n.*\n" -> ""
-//@ normalize-stderr-test "(error: internal compiler error: [^:]+):\d+:\d+: " -> "$1:LL:CC: "
-//@ normalize-stderr-test "delayed at .*" -> ""
-//@ rustc-env:RUST_BACKTRACE=0
+//@ check-pass
+// If this test starts failing because it ICEs due to not being able to convert a `ReErased` to
+// something then feel free to just convert this to a known-bug. I'm pretty sure this is still
+// a failing test, we just started masking the bug.
 
 #![allow(incomplete_features)]
 #![feature(adt_const_params, generic_const_exprs)]
diff --git a/tests/ui/const-generics/issues/issue-105821.stderr b/tests/ui/const-generics/issues/issue-105821.stderr
deleted file mode 100644
index 1f0fc0f33ce..00000000000
--- a/tests/ui/const-generics/issues/issue-105821.stderr
+++ /dev/null
@@ -1,8 +0,0 @@
-error: internal compiler error: compiler/rustc_borrowck/src/universal_regions.rs:LL:CC: cannot convert `'{erased}` to a region vid
-
-query stack during panic:
-#0 [mir_borrowck] borrow-checking `<impl at $DIR/issue-105821.rs:21:1: 23:24>::R`
-#1 [analysis] running analysis passes on this crate
-end of query stack
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/consts/eval_type_mismatch.stderr b/tests/ui/consts/eval_type_mismatch.stderr
deleted file mode 100644
index 38d6e33d406..00000000000
--- a/tests/ui/consts/eval_type_mismatch.stderr
+++ /dev/null
@@ -1,34 +0,0 @@
-error: the constant `A` is not of type `i64`
-  --> $DIR/eval_type_mismatch.rs:5:38
-   |
-LL | impl<const A: usize, const B: usize> Outer<A, B>
-   |                                      ^^^^^^^^^^^ expected `i64`, found `usize`
-   |
-note: required by a bound in `Outer`
-  --> $DIR/eval_type_mismatch.rs:4:14
-   |
-LL | struct Outer<const A: i64, const B: usize>();
-   |              ^^^^^^^^^^^^ required by this bound in `Outer`
-
-error[E0599]: no function or associated item named `o` found for struct `Outer<1, 1>` in the current scope
-  --> $DIR/eval_type_mismatch.rs:15:20
-   |
-LL | struct Outer<const A: i64, const B: usize>();
-   | ------------------------------------------ function or associated item `o` not found for this struct
-...
-LL |     Outer::<1, 1>::o();
-   |                    ^ function or associated item not found in `Outer<1, 1>`
-   |
-   = note: the function or associated item was found for
-           - `Outer<A, B>`
-
-error[E0308]: mismatched types
-  --> $DIR/eval_type_mismatch.rs:5:44
-   |
-LL | impl<const A: usize, const B: usize> Outer<A, B>
-   |                                            ^ expected `i64`, found `usize`
-
-error: aborting due to 3 previous errors
-
-Some errors have detailed explanations: E0308, E0599.
-For more information about an error, try `rustc --explain E0308`.
diff --git a/tests/ui/inference/issue-83606.rs b/tests/ui/inference/issue-83606.rs
index 4454b5e60f0..e6e291c3a92 100644
--- a/tests/ui/inference/issue-83606.rs
+++ b/tests/ui/inference/issue-83606.rs
@@ -6,5 +6,5 @@ fn foo<const N: usize>(_: impl std::fmt::Display) -> [usize; N] {
 
 fn main() {
     let _ = foo("foo");
-    //~^ ERROR type annotations needed for `[usize; _]`
+    //~^ ERROR type annotations needed
 }
diff --git a/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs b/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs
index 4d1cd4332fe..f89a463bc58 100644
--- a/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs
+++ b/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs
@@ -7,8 +7,7 @@ struct S<const L: usize>;
 
 impl<const N: i32> Copy for S<N> {}
 //~^ ERROR: mismatched types
-//~| ERROR: the trait bound `S<N>: Clone` is not satisfied
-//~| ERROR: the constant `N` is not of type `usize`
 impl<const M: usize> Copy for S<M> {}
+//~^ ERROR: conflicting implementations of trait `Copy` for type `S<_>`
 
 fn main() {}
diff --git a/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.stderr b/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.stderr
index 716a4787948..1dac58e1f69 100644
--- a/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.stderr
+++ b/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.stderr
@@ -1,29 +1,11 @@
-error[E0277]: the trait bound `S<N>: Clone` is not satisfied
-  --> $DIR/bad-const-wf-doesnt-specialize.rs:8:29
+error[E0119]: conflicting implementations of trait `Copy` for type `S<_>`
+  --> $DIR/bad-const-wf-doesnt-specialize.rs:10:1
    |
 LL | impl<const N: i32> Copy for S<N> {}
-   |                             ^^^^ the trait `Clone` is not implemented for `S<N>`
-   |
-   = help: the trait `Clone` is implemented for `S<L>`
-note: required by a bound in `Copy`
-  --> $SRC_DIR/core/src/marker.rs:LL:COL
-help: consider annotating `S<N>` with `#[derive(Clone)]`
-   |
-LL + #[derive(Clone)]
-LL | struct S<const L: usize>;
-   |
-
-error: the constant `N` is not of type `usize`
-  --> $DIR/bad-const-wf-doesnt-specialize.rs:8:29
-   |
-LL | impl<const N: i32> Copy for S<N> {}
-   |                             ^^^^ expected `usize`, found `i32`
-   |
-note: required by a bound in `S`
-  --> $DIR/bad-const-wf-doesnt-specialize.rs:6:10
-   |
-LL | struct S<const L: usize>;
-   |          ^^^^^^^^^^^^^^ required by this bound in `S`
+   | -------------------------------- first implementation here
+LL |
+LL | impl<const M: usize> Copy for S<M> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `S<_>`
 
 error[E0308]: mismatched types
   --> $DIR/bad-const-wf-doesnt-specialize.rs:8:31
@@ -31,7 +13,7 @@ error[E0308]: mismatched types
 LL | impl<const N: i32> Copy for S<N> {}
    |                               ^ expected `usize`, found `i32`
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0277, E0308.
-For more information about an error, try `rustc --explain E0277`.
+Some errors have detailed explanations: E0119, E0308.
+For more information about an error, try `rustc --explain E0119`.