Auto merge of rust-lang#157617 - Shourya742:2026-06-08-donot-eagerly-normalize-alias-during-coherence, r=lcnr

bors · bors · commit 4e391cf2425c · 2026-06-12T23:56:07.000Z
Do not eagerly normalize alias during coherence closes: rust-lang#157407 r? @lcnr
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -278,10 +278,16 @@ fn overlap<'tcx>(
     // empty environment.
     let param_env = ty::ParamEnv::empty();
 
-    let impl1_header =
-        fresh_impl_header_normalized(selcx.infcx, param_env, impl1_def_id, is_of_trait);
-    let impl2_header =
-        fresh_impl_header_normalized(selcx.infcx, param_env, impl2_def_id, is_of_trait);
+    let impl1_header = if tcx.next_trait_solver_in_coherence() {
+        fresh_impl_header(selcx.infcx, impl1_def_id, is_of_trait)
+    } else {
+        fresh_impl_header_normalized(selcx.infcx, param_env, impl1_def_id, is_of_trait)
+    };
+    let impl2_header = if tcx.next_trait_solver_in_coherence() {
+        fresh_impl_header(selcx.infcx, impl2_def_id, is_of_trait)
+    } else {
+        fresh_impl_header_normalized(selcx.infcx, param_env, impl2_def_id, is_of_trait)
+    };
 
     // Equate the headers to find their intersection (the general type, with infer vars,
     // that may apply both impls).
diff --git a/tests/ui/associated-types/associated-types-coherence-failure.stderr b/tests/ui/associated-types/associated-types-coherence-failure.stderr
@@ -1,20 +1,20 @@
-error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `Cow<'_, _>`
+error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `<_ as ToOwned>::Owned`
   --> $DIR/associated-types-coherence-failure.rs:21:1
    |
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwned {
    | ----------------------------------------------------------------------------- first implementation here
 ...
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for Cow<'a, B> where B: ToOwned {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Cow<'_, _>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<_ as ToOwned>::Owned`
 
-error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `&_`
+error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `<_ as ToOwned>::Owned`
   --> $DIR/associated-types-coherence-failure.rs:28:1
    |
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwned {
    | ----------------------------------------------------------------------------- first implementation here
 ...
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for &'a B where B: ToOwned {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<_ as ToOwned>::Owned`
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/coherence/coherence-with-closure.stderr b/tests/ui/coherence/coherence-with-closure.stderr
@@ -1,10 +1,10 @@
-error[E0119]: conflicting implementations of trait `Trait` for type `Wrapper<_>`
+error[E0119]: conflicting implementations of trait `Trait` for type `Wrapper<OpaqueClosure>`
   --> $DIR/coherence-with-closure.rs:12:1
    |
 LL | impl Trait for Wrapper<OpaqueClosure> {}
    | ------------------------------------- first implementation here
 LL | impl<T: Sync> Trait for Wrapper<T> {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Wrapper<_>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Wrapper<OpaqueClosure>`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/coherence/coherence-with-coroutine.stock.stderr b/tests/ui/coherence/coherence-with-coroutine.stock.stderr
@@ -1,10 +1,10 @@
-error[E0119]: conflicting implementations of trait `Trait` for type `Wrapper<_>`
+error[E0119]: conflicting implementations of trait `Trait` for type `Wrapper<OpaqueCoroutine>`
   --> $DIR/coherence-with-coroutine.rs:23:1
    |
 LL | impl Trait for Wrapper<OpaqueCoroutine> {}
    | --------------------------------------- first implementation here
 LL | impl<T: Sync> Trait for Wrapper<T> {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Wrapper<_>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Wrapper<OpaqueCoroutine>`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/coherence/normalize-for-errors.stderr b/tests/ui/coherence/normalize-for-errors.stderr
@@ -1,11 +1,11 @@
-error[E0119]: conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>, _)`
+error[E0119]: conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>, <_ as Iterator>::Item)`
   --> $DIR/normalize-for-errors.rs:13:1
    |
 LL | impl<T: Copy, S: Iterator> MyTrait<S> for (T, S::Item) {}
    | ------------------------------------------------------ first implementation here
 LL |
 LL | impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, _)`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, <_ as Iterator>::Item)`
    |
    = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions
    = note: upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions
diff --git a/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.rs b/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.rs
@@ -28,6 +28,9 @@ mod v20 {
     impl<const v10: usize> v17<v10, v2> {
     //~^ ERROR: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
     //~| ERROR: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
+    //~| ERROR: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
+    //~| ERROR: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
+    //~| ERROR: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
     //~| ERROR: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
         pub const fn v21() -> v18 {
             //~^ ERROR cannot find type `v18` in this scope
diff --git a/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.stderr b/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.stderr
@@ -1,5 +1,5 @@
 error[E0432]: unresolved import `v20::v13`
-  --> $DIR/unevaluated-const-ice-119731.rs:39:15
+  --> $DIR/unevaluated-const-ice-119731.rs:42:15
    |
 LL | pub use v20::{v13, v17};
    |               ^^^ no `v13` in `v20`
@@ -32,7 +32,7 @@ LL +         pub const fn v21() -> v11 {}
    |
 
 error[E0425]: cannot find type `v18` in this scope
-  --> $DIR/unevaluated-const-ice-119731.rs:32:31
+  --> $DIR/unevaluated-const-ice-119731.rs:35:31
    |
 LL |     pub type v11 = [[usize; v4]; v4];
    |     --------------------------------- similarly named type alias `v11` defined here
@@ -47,7 +47,7 @@ LL +         pub const fn v21() -> v11 {
    |
 
 error[E0422]: cannot find struct, variant or union type `v18` in this scope
-  --> $DIR/unevaluated-const-ice-119731.rs:34:13
+  --> $DIR/unevaluated-const-ice-119731.rs:37:13
    |
 LL |     pub type v11 = [[usize; v4]; v4];
    |     --------------------------------- similarly named type alias `v11` defined here
@@ -115,6 +115,30 @@ LL |     impl<const v10: usize> v17<v10, v2> {
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
+error: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
+  --> $DIR/unevaluated-const-ice-119731.rs:28:37
+   |
+LL |     impl<const v10: usize> v17<v10, v2> {
+   |                                     ^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
+  --> $DIR/unevaluated-const-ice-119731.rs:28:37
+   |
+LL |     impl<const v10: usize> v17<v10, v2> {
+   |                                     ^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
+  --> $DIR/unevaluated-const-ice-119731.rs:28:37
+   |
+LL |     impl<const v10: usize> v17<v10, v2> {
+   |                                     ^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error[E0592]: duplicate definitions with name `v21`
   --> $DIR/unevaluated-const-ice-119731.rs:23:9
    |
@@ -124,7 +148,7 @@ LL |         pub const fn v21() -> v18 {}
 LL |         pub const fn v21() -> v18 {
    |         ------------------------- other definition for `v21`
 
-error: aborting due to 11 previous errors; 2 warnings emitted
+error: aborting due to 14 previous errors; 2 warnings emitted
 
 Some errors have detailed explanations: E0422, E0425, E0432, E0592.
 For more information about an error, try `rustc --explain E0422`.
diff --git a/tests/ui/const-generics/issues/issue-89304.rs b/tests/ui/const-generics/issues/issue-89304.rs
@@ -1,17 +1,17 @@
+//@ check-pass
+
 #![feature(generic_const_exprs)]
 #![allow(incomplete_features)]
 
 struct GenericStruct<const T: usize> { val: i64 }
 
 impl<const T: usize> From<GenericStruct<T>> for GenericStruct<{T + 1}> {
-//~^ ERROR: conflicting implementations of trait `From<GenericStruct<_>>` for type `GenericStruct<_>`
     fn from(other: GenericStruct<T>) -> Self {
         Self { val: other.val }
     }
 }
 
 impl<const T: usize> From<GenericStruct<{T + 1}>> for GenericStruct<T> {
-//~^ ERROR: conflicting implementations of trait `From<GenericStruct<_>>` for type `GenericStruct<_>`
     fn from(other: GenericStruct<{T + 1}>) -> Self {
         Self { val: other.val }
     }
diff --git a/tests/ui/const-generics/issues/issue-89304.stderr b/tests/ui/const-generics/issues/issue-89304.stderr
diff --git a/tests/ui/specialization/coherence/default-item-normalization-ambig-1.stderr b/tests/ui/specialization/coherence/default-item-normalization-ambig-1.stderr
@@ -1,10 +1,10 @@
-error[E0119]: conflicting implementations of trait `Y`
+error[E0119]: conflicting implementations of trait `Y` for type `<() as X>::U`
   --> $DIR/default-item-normalization-ambig-1.rs:20:1
    |
 LL | impl Y for <() as X>::U {}
    | ----------------------- first implementation here
 LL | impl Y for <i32 as X>::U {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+   | ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<() as X>::U`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/traits/next-solver/alias-relate/alias_eq_substs_eq_not_intercrate.stderr b/tests/ui/traits/next-solver/alias-relate/alias_eq_substs_eq_not_intercrate.stderr
@@ -1,10 +1,10 @@
-error[E0119]: conflicting implementations of trait `Overlaps<Box<_>>`
+error[E0119]: conflicting implementations of trait `Overlaps<Box<_>>` for type `<_ as TraitB>::Assoc`
   --> $DIR/alias_eq_substs_eq_not_intercrate.rs:14:1
    |
 LL | impl<T: TraitB> Overlaps<Box<T>> for <T as TraitB>::Assoc {}
    | --------------------------------------------------------- first implementation here
 LL | impl<U: TraitB> Overlaps<U> for <U as TraitB>::Assoc {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<_ as TraitB>::Assoc`
    |
    = note: downstream crates may implement trait `TraitB` for type `std::boxed::Box<_>`
 
diff --git a/tests/ui/traits/next-solver/coherence/auxiliary/coherence-unknowable-does-not-eagerly-normalize-dep.rs b/tests/ui/traits/next-solver/coherence/auxiliary/coherence-unknowable-does-not-eagerly-normalize-dep.rs
@@ -0,0 +1,10 @@
+// Based on this: https://rust-lang.zulipchat.com/#narrow/channel/326866-t-types.2Fnominated/topic/.23157407.3A.201.2E97.20beta.20regression.3A.20.22conflicting.20implementations.E2.80.A6/near/601113926
+pub trait Row {
+    type Database;
+}
+
+pub struct PgRow;
+
+impl Row for PgRow {
+    type Database = ();
+}
diff --git a/tests/ui/traits/next-solver/coherence/coherence-unknowable-does-not-eagerly-normalize.rs b/tests/ui/traits/next-solver/coherence/coherence-unknowable-does-not-eagerly-normalize.rs
@@ -0,0 +1,28 @@
+//@ compile-flags: -Znext-solver=coherence
+//@ check-pass
+//@ aux-build:coherence-unknowable-does-not-eagerly-normalize-dep.rs
+//
+// Refer issue: https://github.com/rust-lang/rust/issues/157407
+//
+// The reason this regression happened is because `<PgRow as Row>::Database`
+// does not get normalized to `()`, but instead
+// `ActivityType: Decode<<PgRow as Row>::Database>` gets treated like
+// `ActivityType: Decode<?unconstrained>`, staying ambiguous.
+// Now it is considered that a downstream crate may provide such an impl, even
+// though `<PgRow as Row>::Database` can only normalize to a local or upstream
+// type, thus causing this.
+
+extern crate coherence_unknowable_does_not_eagerly_normalize_dep as dep;
+
+use dep::{PgRow, Row};
+
+trait FromRow {}
+trait Decode<T> {}
+
+struct ActivityType;
+
+impl FromRow for PgRow {}
+
+impl<R: Row> FromRow for R where ActivityType: Decode<R::Database> {}
+
+fn main() {}
diff --git a/tests/ui/traits/next-solver/coherence/trait_ref_is_knowable-norm-overflow.stderr b/tests/ui/traits/next-solver/coherence/trait_ref_is_knowable-norm-overflow.stderr
@@ -7,8 +7,7 @@ LL | struct LocalTy;
 LL | impl Trait for <LocalTy as Overflow>::Assoc {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
    |
-   = note: overflow evaluating the requirement `<LocalTy as Overflow>::Assoc == _`
-   = note: overflow evaluating the requirement `<LocalTy as Overflow>::Assoc == _`
+   = note: overflow evaluating the requirement `_ == <LocalTy as Overflow>::Assoc`
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`trait_ref_is_knowable_norm_overflow`)
 
 error: aborting due to 1 previous error
diff --git a/tests/ui/traits/next-solver/cycles/unproductive-in-coherence.rs b/tests/ui/traits/next-solver/cycles/unproductive-in-coherence.rs
@@ -16,6 +16,6 @@ impl Trait for Overflow {
 trait Overlap<T, WfHack> {}
 impl<T: Trait, U: Copy> Overlap<T::Assoc<T>, U> for T {}
 impl<U> Overlap<u32, U> for Overflow {}
-//~^ ERROR: conflicting implementations of trait `Overlap<u32, _>` for type
+//~^ ERROR: conflicting implementations of trait `Overlap<<Overflow as Trait>::Assoc<Overflow>, _>` for type `Overflow` [E0119]
 
 fn main() {}
diff --git a/tests/ui/traits/next-solver/cycles/unproductive-in-coherence.stderr b/tests/ui/traits/next-solver/cycles/unproductive-in-coherence.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `Overlap<u32, _>` for type `Overflow`
+error[E0119]: conflicting implementations of trait `Overlap<<Overflow as Trait>::Assoc<Overflow>, _>` for type `Overflow`
   --> $DIR/unproductive-in-coherence.rs:18:1
    |
 LL | impl<T: Trait, U: Copy> Overlap<T::Assoc<T>, U> for T {}
diff --git a/tests/ui/type-alias-impl-trait/coherence/coherence_cross_crate.stderr b/tests/ui/type-alias-impl-trait/coherence/coherence_cross_crate.stderr
@@ -1,10 +1,10 @@
-error[E0119]: conflicting implementations of trait `OtherTrait` for type `i32`
+error[E0119]: conflicting implementations of trait `OtherTrait` for type `Alias`
   --> $DIR/coherence_cross_crate.rs:22:1
    |
 LL | impl OtherTrait for Alias {}
    | ------------------------- first implementation here
 LL | impl OtherTrait for i32 {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `i32`
+   | ^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Alias`
    |
    = note: upstream crates may add a new impl of trait `coherence_cross_crate_trait_decl::SomeTrait` for type `i32` in future versions
 
diff --git a/tests/ui/type-alias-impl-trait/coherence/coherence_different_hidden_ty.stderr b/tests/ui/type-alias-impl-trait/coherence/coherence_different_hidden_ty.stderr
@@ -1,11 +1,11 @@
-error[E0119]: conflicting implementations of trait `Trait` for type `(u32, i32)`
+error[E0119]: conflicting implementations of trait `Trait` for type `(TAIT, TAIT)`
   --> $DIR/coherence_different_hidden_ty.rs:20:1
    |
 LL | impl Trait for (TAIT, TAIT) {}
    | --------------------------- first implementation here
 LL |
 LL | impl Trait for (u32, i32) {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(u32, i32)`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(TAIT, TAIT)`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/type-alias-impl-trait/impl_trait_for_same_tait.stderr b/tests/ui/type-alias-impl-trait/impl_trait_for_same_tait.stderr
@@ -1,29 +1,29 @@
-error[E0119]: conflicting implementations of trait `Bop`
+error[E0119]: conflicting implementations of trait `Bop` for type `Bar<()>`
   --> $DIR/impl_trait_for_same_tait.rs:18:1
    |
 LL | impl Bop for Bar<()> {}
    | -------------------- first implementation here
 ...
 LL | impl Bop for Bar<i32> {}
-   | ^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+   | ^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Bar<()>`
 
-error[E0119]: conflicting implementations of trait `Bop`
+error[E0119]: conflicting implementations of trait `Bop` for type `Bar<()>`
   --> $DIR/impl_trait_for_same_tait.rs:28:1
    |
 LL | impl Bop for Bar<()> {}
    | -------------------- first implementation here
 ...
 LL | impl Bop for Barr {}
-   | ^^^^^^^^^^^^^^^^^ conflicting implementation
+   | ^^^^^^^^^^^^^^^^^ conflicting implementation for `Bar<()>`
 
-error[E0119]: conflicting implementations of trait `Bop` for type `i32`
+error[E0119]: conflicting implementations of trait `Bop` for type `Bar<()>`
   --> $DIR/impl_trait_for_same_tait.rs:32:1
    |
 LL | impl Bop for Bar<()> {}
    | -------------------- first implementation here
 ...
 LL | impl Bop for i32 {}
-   | ^^^^^^^^^^^^^^^^ conflicting implementation for `i32`
+   | ^^^^^^^^^^^^^^^^ conflicting implementation for `Bar<()>`
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/type-alias-impl-trait/implied_lifetime_wf_check.error.stderr b/tests/ui/type-alias-impl-trait/implied_lifetime_wf_check.error.stderr
@@ -1,11 +1,11 @@
-error[E0119]: conflicting implementations of trait `Yay` for type `i32`
+error[E0119]: conflicting implementations of trait `Yay` for type `<() as HideIt>::Assoc`
   --> $DIR/implied_lifetime_wf_check.rs:27:1
    |
 LL | impl Yay for <() as HideIt>::Assoc {}
    | ---------------------------------- first implementation here
 LL | #[cfg(error)]
 LL | impl Yay for i32 {}
-   | ^^^^^^^^^^^^^^^^ conflicting implementation for `i32`
+   | ^^^^^^^^^^^^^^^^ conflicting implementation for `<() as HideIt>::Assoc`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.current.stderr b/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.current.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `Trait<(), _>`
+error[E0119]: conflicting implementations of trait `Trait<Bar, _>`
   --> $DIR/issue-84660-unsoundness.rs:31:1
    |
 LL | impl<In, Out> Trait<Bar, In> for Out {
diff --git a/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.next.stderr b/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.next.stderr
@@ -1,4 +1,4 @@
-error[E0119]: conflicting implementations of trait `Trait<(), _>`
+error[E0119]: conflicting implementations of trait `Trait<Bar, _>`
   --> $DIR/issue-84660-unsoundness.rs:31:1
    |
 LL | impl<In, Out> Trait<Bar, In> for Out {

Original file line number	Diff line number	Diff line change
`@@ -1,11 +1,11 @@`
`1`		-error[E0119]: conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>, _)`
	`1`	+error[E0119]: conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>, <_ as Iterator>::Item)`
`2`	`2`	`--> $DIR/normalize-for-errors.rs:13:1`
`3`	`3`	`\|`
`4`	`4`	`LL \| impl<T: Copy, S: Iterator> MyTrait<S> for (T, S::Item) {}`
`5`	`5`	`\| ------------------------------------------------------ first implementation here`
`6`	`6`	`LL \|`
`7`	`7`	`LL \| impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {}`
`8`		- \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, _)`
	`8`	+ \| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, <_ as Iterator>::Item)`
`9`	`9`	`\|`
`10`	`10`	= note: upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions
`11`	`11`	= note: upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions
Original file line number	Diff line number	Diff line change
`@@ -1,17 +1,17 @@`
	`1`	`+//@ check-pass`
	`2`	`+`
`1`	`3`	`#![feature(generic_const_exprs)]`
`2`	`4`	`#![allow(incomplete_features)]`
`3`	`5`
`4`	`6`	`struct GenericStruct<const T: usize> { val: i64 }`
`5`	`7`
`6`	`8`	`impl<const T: usize> From<GenericStruct<T>> for GenericStruct<{T + 1}> {`
`7`		-//~^ ERROR: conflicting implementations of trait `From<GenericStruct<_>>` for type `GenericStruct<_>`
`8`	`9`	`fn from(other: GenericStruct<T>) -> Self {`
`9`	`10`	`Self { val: other.val }`
`10`	`11`	`}`
`11`	`12`	`}`
`12`	`13`
`13`	`14`	`impl<const T: usize> From<GenericStruct<{T + 1}>> for GenericStruct<T> {`
`14`		-//~^ ERROR: conflicting implementations of trait `From<GenericStruct<_>>` for type `GenericStruct<_>`
`15`	`15`	`fn from(other: GenericStruct<{T + 1}>) -> Self {`
`16`	`16`	`Self { val: other.val }`
`17`	`17`	`}`