Detect mistyped associated consts in `Instance::resolve`.

20 files changed, 142 insertions, 52 deletions

diff --git a/Cargo.lock b/Cargo.lock
index cf86f44305e..f3d226b30f7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4310,6 +4310,7 @@ version = "0.0.0"
 dependencies = [
  "log",
  "rustc_data_structures",
+ "rustc_errors",
  "rustc_hir",
  "rustc_infer",
  "rustc_middle",
diff --git a/src/librustc_codegen_llvm/context.rs b/src/librustc_codegen_llvm/context.rs
index daa723495f6..d385c073074 100644
--- a/src/librustc_codegen_llvm/context.rs
+++ b/src/librustc_codegen_llvm/context.rs
@@ -376,6 +376,7 @@ impl MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     def_id,
                     tcx.intern_substs(&[]),
                 )
+                .unwrap()
                 .unwrap(),
             ),
             _ => {
diff --git a/src/librustc_codegen_ssa/base.rs b/src/librustc_codegen_ssa/base.rs
index 8a9b8f11f76..1577dbbd350 100644
--- a/src/librustc_codegen_ssa/base.rs
+++ b/src/librustc_codegen_ssa/base.rs
@@ -468,6 +468,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                     start_def_id,
                     cx.tcx().intern_substs(&[main_ret_ty.into()]),
                 )
+                .unwrap()
                 .unwrap(),
             );
             (
diff --git a/src/librustc_codegen_ssa/mir/block.rs b/src/librustc_codegen_ssa/mir/block.rs
index 49131386508..112833845e5 100644
--- a/src/librustc_codegen_ssa/mir/block.rs
+++ b/src/librustc_codegen_ssa/mir/block.rs
@@ -537,6 +537,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             ty::FnDef(def_id, substs) => (
                 Some(
                     ty::Instance::resolve(bx.tcx(), ty::ParamEnv::reveal_all(), def_id, substs)
+                        .unwrap()
                         .unwrap(),
                 ),
                 None,
diff --git a/src/librustc_middle/mir/interpret/queries.rs b/src/librustc_middle/mir/interpret/queries.rs
index 46bf1d96957..a7953f0f900 100644
--- a/src/librustc_middle/mir/interpret/queries.rs
+++ b/src/librustc_middle/mir/interpret/queries.rs
@@ -39,12 +39,13 @@ impl<'tcx> TyCtxt<'tcx> {
         promoted: Option<mir::Promoted>,
         span: Option<Span>,
     ) -> ConstEvalResult<'tcx> {
-        let instance = ty::Instance::resolve(self, param_env, def_id, substs);
-        if let Some(instance) = instance {
-            let cid = GlobalId { instance, promoted };
-            self.const_eval_global_id(param_env, cid, span)
-        } else {
-            Err(ErrorHandled::TooGeneric)
+        match ty::Instance::resolve(self, param_env, def_id, substs) {
+            Ok(Some(instance)) => {
+                let cid = GlobalId { instance, promoted };
+                self.const_eval_global_id(param_env, cid, span)
+            }
+            Ok(None) => Err(ErrorHandled::TooGeneric),
+            Err(error_reported) => Err(ErrorHandled::Reported(error_reported)),
         }
     }
 
diff --git a/src/librustc_middle/query/mod.rs b/src/librustc_middle/query/mod.rs
index c974ab3190e..6e56b364760 100644
--- a/src/librustc_middle/query/mod.rs
+++ b/src/librustc_middle/query/mod.rs
@@ -679,7 +679,7 @@ rustc_queries! {
     Codegen {
         query codegen_fulfill_obligation(
             key: (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>)
-        ) -> Option<Vtable<'tcx, ()>> {
+        ) -> Result<Vtable<'tcx, ()>, ErrorReported> {
             cache_on_disk_if { true }
             desc { |tcx|
                 "checking if `{}` fulfills its obligations",
@@ -1258,9 +1258,18 @@ rustc_queries! {
             desc { "looking up enabled feature gates" }
         }
 
+        /// Attempt to resolve the given `DefId` to an `Instance`, for the
+        /// given generics args (`SubstsRef`), returning one of:
+        ///  * `Ok(Some(instance))` on success
+        ///  * `Ok(None)` when the `SubstsRef` are still too generic,
+        ///    and therefore don't allow finding the final `Instance`
+        ///  * `Err(ErrorReported)` when the `Instance` resolution process
+        ///    couldn't complete due to errors elsewhere - this is distinct
+        ///    from `Ok(None)` to avoid misleading diagnostics when an error
+        ///    has already been/will be emitted, for the original cause
         query resolve_instance(
             key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>
-        ) -> Option<ty::Instance<'tcx>> {
+        ) -> Result<Option<ty::Instance<'tcx>>, ErrorReported> {
             desc { "resolving instance `{}`", ty::Instance::new(key.value.0, key.value.1) }
         }
     }
diff --git a/src/librustc_middle/ty/instance.rs b/src/librustc_middle/ty/instance.rs
index 0366795a20e..d7b59d5fa13 100644
--- a/src/librustc_middle/ty/instance.rs
+++ b/src/librustc_middle/ty/instance.rs
@@ -1,6 +1,7 @@
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::ty::print::{FmtPrinter, Printer};
 use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeFoldable};
+use rustc_errors::ErrorReported;
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_hir::lang_items::DropInPlaceFnLangItem;
@@ -268,26 +269,31 @@ impl<'tcx> Instance<'tcx> {
     /// this is used to find the precise code that will run for a trait method invocation,
     /// if known.
     ///
-    /// Returns `None` if we cannot resolve `Instance` to a specific instance.
+    /// Returns `Ok(None)` if we cannot resolve `Instance` to a specific instance.
     /// For example, in a context like this,
     ///
     /// ```
     /// fn foo<T: Debug>(t: T) { ... }
     /// ```
     ///
-    /// trying to resolve `Debug::fmt` applied to `T` will yield `None`, because we do not
+    /// trying to resolve `Debug::fmt` applied to `T` will yield `Ok(None)`, because we do not
     /// know what code ought to run. (Note that this setting is also affected by the
     /// `RevealMode` in the parameter environment.)
     ///
     /// Presuming that coherence and type-check have succeeded, if this method is invoked
     /// in a monomorphic context (i.e., like during codegen), then it is guaranteed to return
-    /// `Some`.
+    /// `Ok(Some(instance))`.
+    ///
+    /// Returns `Err(ErrorReported)` when the `Instance` resolution process
+    /// couldn't complete due to errors elsewhere - this is distinct
+    /// from `Ok(None)` to avoid misleading diagnostics when an error
+    /// has already been/will be emitted, for the original cause
     pub fn resolve(
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         def_id: DefId,
         substs: SubstsRef<'tcx>,
-    ) -> Option<Instance<'tcx>> {
+    ) -> Result<Option<Instance<'tcx>>, ErrorReported> {
         // All regions in the result of this query are erased, so it's
         // fine to erase all of the input regions.
 
@@ -307,7 +313,7 @@ impl<'tcx> Instance<'tcx> {
         substs: SubstsRef<'tcx>,
     ) -> Option<Instance<'tcx>> {
         debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
-        Instance::resolve(tcx, param_env, def_id, substs).map(|mut resolved| {
+        Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
             match resolved.def {
                 InstanceDef::Item(def_id) if resolved.def.requires_caller_location(tcx) => {
                     debug!(" => fn pointer created for function with #[track_caller]");
@@ -339,7 +345,7 @@ impl<'tcx> Instance<'tcx> {
             debug!(" => associated item with unsizeable self: Self");
             Some(Instance { def: InstanceDef::VtableShim(def_id), substs })
         } else {
-            Instance::resolve(tcx, param_env, def_id, substs)
+            Instance::resolve(tcx, param_env, def_id, substs).ok().flatten()
         }
     }
 
@@ -360,7 +366,7 @@ impl<'tcx> Instance<'tcx> {
     pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
         let def_id = tcx.require_lang_item(DropInPlaceFnLangItem, None);
         let substs = tcx.intern_substs(&[ty.into()]);
-        Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap()
+        Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap().unwrap()
     }
 
     pub fn fn_once_adapter_instance(
diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index fcbb2535797..18efc736d2a 100644
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -453,8 +453,13 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         trace!("resolve: {:?}, {:#?}", def_id, substs);
         trace!("param_env: {:#?}", self.param_env);
         trace!("substs: {:#?}", substs);
-        ty::Instance::resolve(*self.tcx, self.param_env, def_id, substs)
-            .ok_or_else(|| err_inval!(TooGeneric).into())
+        match ty::Instance::resolve(*self.tcx, self.param_env, def_id, substs) {
+            Ok(Some(instance)) => Ok(instance),
+            Ok(None) => throw_inval!(TooGeneric),
+
+            // FIXME(eddyb) this could be a bit more specific than `TypeckError`.
+            Err(error_reported) => throw_inval!(TypeckError(error_reported)),
+        }
     }
 
     pub fn layout_of_local(
diff --git a/src/librustc_mir/monomorphize/collector.rs b/src/librustc_mir/monomorphize/collector.rs
index 32d28bb0d13..efb5e24bf96 100644
--- a/src/librustc_mir/monomorphize/collector.rs
+++ b/src/librustc_mir/monomorphize/collector.rs
@@ -674,9 +674,12 @@ fn visit_fn_use<'tcx>(
     output: &mut Vec<MonoItem<'tcx>>,
 ) {
     if let ty::FnDef(def_id, substs) = ty.kind {
-        let resolver =
-            if is_direct_call { ty::Instance::resolve } else { ty::Instance::resolve_for_fn_ptr };
-        let instance = resolver(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap();
+        let instance = if is_direct_call {
+            ty::Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap().unwrap()
+        } else {
+            ty::Instance::resolve_for_fn_ptr(tcx, ty::ParamEnv::reveal_all(), def_id, substs)
+                .unwrap()
+        };
         visit_instance_use(tcx, instance, is_direct_call, output);
     }
 }
@@ -1057,6 +1060,7 @@ impl RootCollector<'_, 'v> {
             start_def_id,
             self.tcx.intern_substs(&[main_ret_ty.into()]),
         )
+        .unwrap()
         .unwrap();
 
         self.output.push(create_fn_mono_item(start_instance));
@@ -1112,8 +1116,9 @@ fn create_mono_items_for_default_impls<'tcx>(
                                 trait_ref.substs[param.index as usize]
                             }
                         });
-                    let instance =
-                        ty::Instance::resolve(tcx, param_env, method.def_id, substs).unwrap();
+                    let instance = ty::Instance::resolve(tcx, param_env, method.def_id, substs)
+                        .unwrap()
+                        .unwrap();
 
                     let mono_item = create_fn_mono_item(instance);
                     if mono_item.is_instantiable(tcx) && should_monomorphize_locally(tcx, &instance)
diff --git a/src/librustc_mir/monomorphize/mod.rs b/src/librustc_mir/monomorphize/mod.rs
index bbb8e063a45..98a3d9584f5 100644
--- a/src/librustc_mir/monomorphize/mod.rs
+++ b/src/librustc_mir/monomorphize/mod.rs
@@ -18,7 +18,7 @@ pub fn custom_coerce_unsize_info<'tcx>(
     });
 
     match tcx.codegen_fulfill_obligation((ty::ParamEnv::reveal_all(), trait_ref)) {
-        Some(traits::VtableImpl(traits::VtableImplData { impl_def_id, .. })) => {
+        Ok(traits::VtableImpl(traits::VtableImplData { impl_def_id, .. })) => {
             tcx.coerce_unsized_info(impl_def_id).custom_kind.unwrap()
         }
         vtable => {
diff --git a/src/librustc_mir/transform/check_consts/validation.rs b/src/librustc_mir/transform/check_consts/validation.rs
index 4cc42c0408f..6754831a6fe 100644
--- a/src/librustc_mir/transform/check_consts/validation.rs
+++ b/src/librustc_mir/transform/check_consts/validation.rs
@@ -525,7 +525,7 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
                 if self.tcx.features().const_trait_impl {
                     let instance = Instance::resolve(self.tcx, self.param_env, def_id, substs);
                     debug!("Resolving ({:?}) -> {:?}", def_id, instance);
-                    if let Some(func) = instance {
+                    if let Ok(Some(func)) = instance {
                         if let InstanceDef::Item(def_id) = func.def {
                             if is_const_fn(self.tcx, def_id) {
                                 return;
diff --git a/src/librustc_mir/transform/inline.rs b/src/librustc_mir/transform/inline.rs
index bfa13abb871..f071eb0a952 100644
--- a/src/librustc_mir/transform/inline.rs
+++ b/src/librustc_mir/transform/inline.rs
@@ -178,7 +178,8 @@ impl Inliner<'tcx> {
         let terminator = bb_data.terminator();
         if let TerminatorKind::Call { func: ref op, .. } = terminator.kind {
             if let ty::FnDef(callee_def_id, substs) = op.ty(caller_body, self.tcx).kind {
-                let instance = Instance::resolve(self.tcx, param_env, callee_def_id, substs)?;
+                let instance =
+                    Instance::resolve(self.tcx, param_env, callee_def_id, substs).ok().flatten()?;
 
                 if let InstanceDef::Virtual(..) = instance.def {
                     return None;
diff --git a/src/librustc_mir_build/lints.rs b/src/librustc_mir_build/lints.rs
index 948f1ae0b42..66d56858527 100644
--- a/src/librustc_mir_build/lints.rs
+++ b/src/librustc_mir_build/lints.rs
@@ -72,7 +72,7 @@ impl<'mir, 'tcx> Search<'mir, 'tcx> {
         let func_ty = func.ty(body, tcx);
         if let ty::FnDef(fn_def_id, substs) = func_ty.kind {
             let (call_fn_id, call_substs) =
-                if let Some(instance) = Instance::resolve(tcx, param_env, fn_def_id, substs) {
+                if let Ok(Some(instance)) = Instance::resolve(tcx, param_env, fn_def_id, substs) {
                     (instance.def_id(), instance.substs)
                 } else {
                     (fn_def_id, substs)
diff --git a/src/librustc_trait_selection/traits/codegen/mod.rs b/src/librustc_trait_selection/traits/codegen/mod.rs
index e75432a0b72..b2e46bc6da1 100644
--- a/src/librustc_trait_selection/traits/codegen/mod.rs
+++ b/src/librustc_trait_selection/traits/codegen/mod.rs
@@ -7,6 +7,7 @@ use crate::infer::{InferCtxt, TyCtxtInferExt};
 use crate::traits::{
     FulfillmentContext, Obligation, ObligationCause, SelectionContext, TraitEngine, Vtable,
 };
+use rustc_errors::ErrorReported;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::{self, TyCtxt};
 
@@ -19,7 +20,7 @@ use rustc_middle::ty::{self, TyCtxt};
 pub fn codegen_fulfill_obligation<'tcx>(
     ty: TyCtxt<'tcx>,
     (param_env, trait_ref): (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>),
-) -> Option<Vtable<'tcx, ()>> {
+) -> Result<Vtable<'tcx, ()>, ErrorReported> {
     // Remove any references to regions; this helps improve caching.
     let trait_ref = ty.erase_regions(&trait_ref);
 
@@ -55,7 +56,7 @@ pub fn codegen_fulfill_obligation<'tcx>(
                         trait_ref
                     ),
                 );
-                return None;
+                return Err(ErrorReported);
             }
             Err(e) => {
                 bug!("Encountered error `{:?}` selecting `{:?}` during codegen", e, trait_ref)
@@ -75,7 +76,7 @@ pub fn codegen_fulfill_obligation<'tcx>(
         let vtable = drain_fulfillment_cx_or_panic(&infcx, &mut fulfill_cx, &vtable);
 
         info!("Cache miss: {:?} => {:?}", trait_ref, vtable);
-        Some(vtable)
+        Ok(vtable)
     })
 }
 
diff --git a/src/librustc_ty/Cargo.toml b/src/librustc_ty/Cargo.toml
index 37d1ed38d79..b6db75e44f9 100644
--- a/src/librustc_ty/Cargo.toml
+++ b/src/librustc_ty/Cargo.toml
@@ -12,6 +12,7 @@ path = "lib.rs"
 log = "0.4"
 rustc_middle = { path = "../librustc_middle" }
 rustc_data_structures = { path = "../librustc_data_structures" }
+rustc_errors = { path = "../librustc_errors" }
 rustc_hir = { path = "../librustc_hir" }
 rustc_infer = { path = "../librustc_infer" }
 rustc_span = { path = "../librustc_span" }
diff --git a/src/librustc_ty/instance.rs b/src/librustc_ty/instance.rs
index d50e7f39d41..2a99bb1aed9 100644
--- a/src/librustc_ty/instance.rs
+++ b/src/librustc_ty/instance.rs
@@ -1,3 +1,4 @@
+use rustc_errors::ErrorReported;
 use rustc_hir::def_id::DefId;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::ty::subst::SubstsRef;
@@ -12,7 +13,7 @@ use log::debug;
 fn resolve_instance<'tcx>(
     tcx: TyCtxt<'tcx>,
     key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>,
-) -> Option<Instance<'tcx>> {
+) -> Result<Option<Instance<'tcx>>, ErrorReported> {
     let (param_env, (def_id, substs)) = key.into_parts();
 
     debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
@@ -40,7 +41,7 @@ fn resolve_instance<'tcx>(
                 if ty.needs_drop(tcx, param_env) {
                     // `DropGlue` requires a monomorphic aka concrete type.
                     if ty.needs_subst() {
-                        return None;
+                        return Ok(None);
                     }
 
                     debug!(" => nontrivial drop glue");
@@ -55,7 +56,7 @@ fn resolve_instance<'tcx>(
                 ty::InstanceDef::Item(def_id)
             }
         };
-        Some(Instance { def, substs })
+        Ok(Some(Instance { def, substs }))
     };
     debug!("resolve(def_id={:?}, substs={:?}) = {:?}", def_id, substs, result);
     result
@@ -67,7 +68,7 @@ fn resolve_associated_item<'tcx>(
     param_env: ty::ParamEnv<'tcx>,
     trait_id: DefId,
     rcvr_substs: SubstsRef<'tcx>,
-) -> Option<Instance<'tcx>> {
+) -> Result<Option<Instance<'tcx>>, ErrorReported> {
     let def_id = trait_item.def_id;
     debug!(
         "resolve_associated_item(trait_item={:?}, \
@@ -82,7 +83,7 @@ fn resolve_associated_item<'tcx>(
 
     // Now that we know which impl is being used, we can dispatch to
     // the actual function:
-    match vtbl {
+    Ok(match vtbl {
         traits::VtableImpl(impl_data) => {
             debug!(
                 "resolving VtableImpl: {:?}, {:?}, {:?}, {:?}",
@@ -94,13 +95,11 @@ fn resolve_associated_item<'tcx>(
             let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
             let trait_def = tcx.trait_def(trait_def_id);
             let leaf_def = trait_def
-                .ancestors(tcx, impl_data.impl_def_id)
-                .ok()?
+                .ancestors(tcx, impl_data.impl_def_id)?
                 .leaf_def(tcx, trait_item.ident, trait_item.kind)
                 .unwrap_or_else(|| {
                     bug!("{:?} not found in {:?}", trait_item, impl_data.impl_def_id);
                 });
-            let def_id = leaf_def.item.def_id;
 
             let substs = tcx.infer_ctxt().enter(|infcx| {
                 let param_env = param_env.with_reveal_all();
@@ -135,11 +134,52 @@ fn resolve_associated_item<'tcx>(
             };
 
             if !eligible {
-                return None;
+                return Ok(None);
             }
 
             let substs = tcx.erase_regions(&substs);
-            Some(ty::Instance::new(def_id, substs))
+
+            // Check if we just resolved an associated `const` declaration from
+            // a `trait` to an associated `const` definition in an `impl`, where
+            // the definition in the `impl` has the wrong type (for which an
+            // error has already been/will be emitted elsewhere).
+            //
+            // NB: this may be expensive, we try to skip it in all the cases where
+            // we know the error would've been caught (e.g. in an upstream crate).
+            //
+            // A better approach might be to just introduce a query (returning
+            // `Result<(), ErrorReported>`) for the check that `rustc_typeck`
+            // performs (i.e. that the definition's type in the `impl` matches
+            // the declaration in the `trait`), so that we can cheaply check
+            // here if it failed, instead of approximating it.
+            if trait_item.kind == ty::AssocKind::Const
+                && trait_item.def_id != leaf_def.item.def_id
+                && leaf_def.item.def_id.is_local()
+            {
+                let normalized_type_of = |def_id, substs| {
+                    tcx.subst_and_normalize_erasing_regions(substs, param_env, &tcx.type_of(def_id))
+                };
+
+                let original_ty = normalized_type_of(trait_item.def_id, rcvr_substs);
+                let resolved_ty = normalized_type_of(leaf_def.item.def_id, substs);
+
+                if original_ty != resolved_ty {
+                    let msg = format!(
+                        "Instance::resolve: inconsistent associated `const` type: \
+                         was `{}: {}` but resolved to `{}: {}`",
+                        tcx.def_path_str_with_substs(trait_item.def_id, rcvr_substs),
+                        original_ty,
+                        tcx.def_path_str_with_substs(leaf_def.item.def_id, substs),
+                        resolved_ty,
+                    );
+                    let span = tcx.def_span(leaf_def.item.def_id);
+                    tcx.sess.delay_span_bug(span, &msg);
+
+                    return Err(ErrorReported);
+                }
+            }
+
+            Some(ty::Instance::new(leaf_def.item.def_id, substs))
         }
         traits::VtableGenerator(generator_data) => Some(Instance {
             def: ty::InstanceDef::Item(generator_data.generator_def_id),
@@ -157,7 +197,7 @@ fn resolve_associated_item<'tcx>(
         traits::VtableFnPointer(ref data) => {
             // `FnPtrShim` requires a monomorphic aka concrete type.
             if data.fn_ty.needs_subst() {
-                return None;
+                return Ok(None);
             }
 
             Some(Instance {
@@ -178,7 +218,7 @@ fn resolve_associated_item<'tcx>(
 
                     // `CloneShim` requires a monomorphic aka concrete type.
                     if self_ty.needs_subst() {
-                        return None;
+                        return Ok(None);
                     }
 
                     Some(Instance {
@@ -197,7 +237,7 @@ fn resolve_associated_item<'tcx>(
             }
         }
         traits::VtableAutoImpl(..) | traits::VtableParam(..) | traits::VtableTraitAlias(..) => None,
-    }
+    })
 }
 
 pub fn provide(providers: &mut ty::query::Providers<'_>) {
diff --git a/src/test/ui/consts/issue-70942-trait-vs-impl-mismatch.rs b/src/test/ui/consts/issue-70942-trait-vs-impl-mismatch.rs
new file mode 100644
index 00000000000..b65f5345034
--- /dev/null
+++ b/src/test/ui/consts/issue-70942-trait-vs-impl-mismatch.rs
@@ -0,0 +1,14 @@
+trait Nat {
+    const VALUE: usize;
+}
+
+struct Zero;
+
+impl Nat for Zero {
+    const VALUE: i32 = 0;
+    //~^ ERROR implemented const `VALUE` has an incompatible type for trait
+}
+
+fn main() {
+    let _: [i32; Zero::VALUE] = [];
+}
diff --git a/src/test/ui/consts/issue-70942-trait-vs-impl-mismatch.stderr b/src/test/ui/consts/issue-70942-trait-vs-impl-mismatch.stderr
new file mode 100644
index 00000000000..19d9ff71667
--- /dev/null
+++ b/src/test/ui/consts/issue-70942-trait-vs-impl-mismatch.stderr
@@ -0,0 +1,12 @@
+error[E0326]: implemented const `VALUE` has an incompatible type for trait
+  --> $DIR/issue-70942-trait-vs-impl-mismatch.rs:8:18
+   |
+LL |     const VALUE: usize;
+   |                  ----- type in trait
+...
+LL |     const VALUE: i32 = 0;
+   |                  ^^^ expected `usize`, found `i32`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0326`.
diff --git a/src/test/ui/issues/issue-69602-type-err-during-codegen-ice.rs b/src/test/ui/issues/issue-69602-type-err-during-codegen-ice.rs
index 6ac3eb53cb3..2c5257ce063 100644
--- a/src/test/ui/issues/issue-69602-type-err-during-codegen-ice.rs
+++ b/src/test/ui/issues/issue-69602-type-err-during-codegen-ice.rs
@@ -19,5 +19,4 @@ impl TraitB for B { //~ ERROR not all trait items implemented, missing: `MyA`
 
 fn main() {
     let _ = [0; B::VALUE];
-    //~^ ERROR constant expression depends on a generic parameter
 }
diff --git a/src/test/ui/issues/issue-69602-type-err-during-codegen-ice.stderr b/src/test/ui/issues/issue-69602-type-err-during-codegen-ice.stderr
index 175e6b0eaa0..8ae0f8b804c 100644
--- a/src/test/ui/issues/issue-69602-type-err-during-codegen-ice.stderr
+++ b/src/test/ui/issues/issue-69602-type-err-during-codegen-ice.stderr
@@ -13,15 +13,7 @@ LL |     type MyA: TraitA;
 LL | impl TraitB for B {
    | ^^^^^^^^^^^^^^^^^ missing `MyA` in implementation
 
-error: constant expression depends on a generic parameter
-  --> $DIR/issue-69602-type-err-during-codegen-ice.rs:21:17
-   |
-LL |     let _ = [0; B::VALUE];
-   |                 ^^^^^^^^
-   |
-   = note: this may fail depending on what value the parameter takes
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 Some errors have detailed explanations: E0046, E0437.
 For more information about an error, try `rustc --explain E0046`.