adapted test outputs to the new behaviour: suggesting adding the

TomtheCoder2 · TomtheCoder2 · commit 0b83de8dae02 · 2026-03-11T16:18:15.000+13:00
parameter to the impl struct and the struct definition if used in the
impl body

Signed-off-by: janwi_mac &lt;jan.wilhelm77@gmail.com&gt;
diff --git a/tests/ui/associated-inherent-types/hr-do-not-blame-outlives-static-ice.stderr b/tests/ui/associated-inherent-types/hr-do-not-blame-outlives-static-ice.stderr
@@ -12,6 +12,15 @@ error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait,
    |
 LL | impl<'a> Foo<fn(&())> {
    |      ^^ unconstrained lifetime parameter
+   |
+help: make use of the lifetime parameter `'a` in the `self` type
+   |
+LL | impl<'a> Foo<fn(&()), 'a> {
+   |                     ++++
+help: and add it to the struct definition of Foo as well since it's used in the body of the impl
+   |
+LL | struct Foo<T, 'a>(T);
+   |             ++++
 
 error[E0308]: mismatched types
   --> $DIR/hr-do-not-blame-outlives-static-ice.rs:14:11
diff --git a/tests/ui/associated-types/issue-26262.stderr b/tests/ui/associated-types/issue-26262.stderr
@@ -3,6 +3,15 @@ error[E0207]: the type parameter `T` is not constrained by the impl trait, self
    |
 LL | impl<T: Tr> S<T::Assoc> {
    |      ^ unconstrained type parameter
+   |
+help: make use of the type parameter `T` in the `self` type
+   |
+LL | impl<T: Tr> S<T::Assoc, T> {
+   |                       +++
+help: and add it to the struct definition of S as well since it's used in the body of the impl
+   |
+LL | struct S<T, T>(T);
+   |           +++
 
 error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait, self type, or predicates
   --> $DIR/issue-26262.rs:17:6
diff --git a/tests/ui/associated-types/unconstrained-lifetime-assoc-type.stderr b/tests/ui/associated-types/unconstrained-lifetime-assoc-type.stderr
@@ -3,6 +3,15 @@ error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait,
    |
 LL | impl<'a> Fun for Holder {
    |      ^^ unconstrained lifetime parameter
+   |
+help: make use of the lifetime parameter `'a` in the `self` type
+   |
+LL | impl<'a> Fun for Holder<'a> {
+   |                        ++++
+help: and add it to the struct definition of Holder as well since it's used in the body of the impl
+   |
+LL | struct Holder<'a> {
+   |              ++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/const-generics/ice-unexpected-inference-var-122549.stderr b/tests/ui/const-generics/ice-unexpected-inference-var-122549.stderr
@@ -71,6 +71,14 @@ LL | impl<'a, T, const N: usize> Iterator for ConstChunksExact<'a, T, {}> {
    |
    = note: expressions using a const parameter must map each value to a distinct output value
    = note: proving the result of expressions other than the parameter are unique is not supported
+help: make use of the type parameter `N` in the `self` type
+   |
+LL | impl<'a, T, const N: usize> Iterator for ConstChunksExact<'a, T, {}, N> {
+   |                                                                    +++
+help: and add it to the struct definition of ConstChunksExact as well since it's used in the body of the impl
+   |
+LL | struct ConstChunksExact<'rem, T: 'a, const N: usize, N> {}
+   |                                                    +++
 
 error: aborting due to 8 previous errors
 
diff --git a/tests/ui/const-generics/normalizing_with_unconstrained_impl_params.stderr b/tests/ui/const-generics/normalizing_with_unconstrained_impl_params.stderr
@@ -53,6 +53,14 @@ LL | impl<'a, T: std::fmt::Debug, const N: usize> Iterator for ConstChunksExact<
    |
    = note: expressions using a const parameter must map each value to a distinct output value
    = note: proving the result of expressions other than the parameter are unique is not supported
+help: make use of the type parameter `N` in the `self` type
+   |
+LL | impl<'a, T: std::fmt::Debug, const N: usize> Iterator for ConstChunksExact<'a, T, {}, N> {
+   |                                                                                     +++
+help: and add it to the struct definition of ConstChunksExact as well since it's used in the body of the impl
+   |
+LL | struct ConstChunksExact<'a, T: '_, const assert: usize, N> {}
+   |                                                       +++
 
 error[E0308]: mismatched types
   --> $DIR/normalizing_with_unconstrained_impl_params.rs:6:27
diff --git a/tests/ui/error-codes/E0207.stderr b/tests/ui/error-codes/E0207.stderr
@@ -3,6 +3,15 @@ error[E0207]: the type parameter `T` is not constrained by the impl trait, self
    |
 LL | impl<T: Default> Foo {
    |      ^ unconstrained type parameter
+   |
+help: make use of the type parameter `T` in the `self` type
+   |
+LL | impl<T: Default> Foo<T> {
+   |                     +++
+help: and add it to the struct definition of Foo as well since it's used in the body of the impl
+   |
+LL | struct Foo<T>;
+   |           +++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/generic-associated-types/bugs/issue-87735.stderr b/tests/ui/generic-associated-types/bugs/issue-87735.stderr
@@ -3,6 +3,15 @@ error[E0207]: the type parameter `U` is not constrained by the impl trait, self
    |
 LL | impl<'b, T, U> AsRef2 for Foo<T>
    |             ^ unconstrained type parameter
+   |
+help: make use of the type parameter `U` in the `self` type
+   |
+LL | impl<'b, T, U> AsRef2 for Foo<T, U>
+   |                                +++
+help: and add it to the struct definition of Foo as well since it's used in the body of the impl
+   |
+LL | struct Foo<T, U>(T);
+   |             +++
 
 error[E0309]: the parameter type `U` may not live long enough
   --> $DIR/issue-87735.rs:34:3
diff --git a/tests/ui/issues/issue-22886.stderr b/tests/ui/issues/issue-22886.stderr
@@ -3,6 +3,15 @@ error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait,
    |
 LL | impl<'a> Iterator for Newtype {
    |      ^^ unconstrained lifetime parameter
+   |
+help: make use of the lifetime parameter `'a` in the `self` type
+   |
+LL | impl<'a> Iterator for Newtype<'a> {
+   |                              ++++
+help: and add it to the struct definition of Newtype as well since it's used in the body of the impl
+   |
+LL | struct Newtype<'a>(Option<Box<usize>>);
+   |               ++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/issues/issue-35139.stderr b/tests/ui/issues/issue-35139.stderr
@@ -3,6 +3,15 @@ error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait,
    |
 LL | impl<'a> MethodType for MTFn {
    |      ^^ unconstrained lifetime parameter
+   |
+help: make use of the lifetime parameter `'a` in the `self` type
+   |
+LL | impl<'a> MethodType for MTFn<'a> {
+   |                             ++++
+help: and add it to the struct definition of MTFn as well since it's used in the body of the impl
+   |
+LL | pub struct MTFn<'a>;
+   |                ++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/traits/unconstrained-projection-normalization-2.current.stderr b/tests/ui/traits/unconstrained-projection-normalization-2.current.stderr
@@ -3,6 +3,15 @@ error[E0207]: the type parameter `T` is not constrained by the impl trait, self
    |
 LL | impl<T: ?Sized> Every for Thing {
    |      ^ unconstrained type parameter
+   |
+help: make use of the type parameter `T` in the `self` type
+   |
+LL | impl<T: ?Sized> Every for Thing<T> {
+   |                                +++
+help: and add it to the struct definition of Thing as well since it's used in the body of the impl
+   |
+LL | struct Thing<T>;
+   |             +++
 
 error[E0277]: the size for values of type `T` cannot be known at compilation time
   --> $DIR/unconstrained-projection-normalization-2.rs:16:18
diff --git a/tests/ui/traits/unconstrained-projection-normalization-2.next.stderr b/tests/ui/traits/unconstrained-projection-normalization-2.next.stderr
@@ -3,6 +3,15 @@ error[E0207]: the type parameter `T` is not constrained by the impl trait, self
    |
 LL | impl<T: ?Sized> Every for Thing {
    |      ^ unconstrained type parameter
+   |
+help: make use of the type parameter `T` in the `self` type
+   |
+LL | impl<T: ?Sized> Every for Thing<T> {
+   |                                +++
+help: and add it to the struct definition of Thing as well since it's used in the body of the impl
+   |
+LL | struct Thing<T>;
+   |             +++
 
 error[E0277]: the size for values of type `T` cannot be known at compilation time
   --> $DIR/unconstrained-projection-normalization-2.rs:16:18
diff --git a/tests/ui/traits/unconstrained-projection-normalization.current.stderr b/tests/ui/traits/unconstrained-projection-normalization.current.stderr
@@ -3,6 +3,15 @@ error[E0207]: the type parameter `T` is not constrained by the impl trait, self
    |
 LL | impl<T: ?Sized> Every for Thing {
    |      ^ unconstrained type parameter
+   |
+help: make use of the type parameter `T` in the `self` type
+   |
+LL | impl<T: ?Sized> Every for Thing<T> {
+   |                                +++
+help: and add it to the struct definition of Thing as well since it's used in the body of the impl
+   |
+LL | struct Thing<T>;
+   |             +++
 
 error[E0277]: the size for values of type `T` cannot be known at compilation time
   --> $DIR/unconstrained-projection-normalization.rs:15:18
diff --git a/tests/ui/traits/unconstrained-projection-normalization.next.stderr b/tests/ui/traits/unconstrained-projection-normalization.next.stderr
@@ -3,6 +3,15 @@ error[E0207]: the type parameter `T` is not constrained by the impl trait, self
    |
 LL | impl<T: ?Sized> Every for Thing {
    |      ^ unconstrained type parameter
+   |
+help: make use of the type parameter `T` in the `self` type
+   |
+LL | impl<T: ?Sized> Every for Thing<T> {
+   |                                +++
+help: and add it to the struct definition of Thing as well since it's used in the body of the impl
+   |
+LL | struct Thing<T>;
+   |             +++
 
 error[E0277]: the size for values of type `T` cannot be known at compilation time
   --> $DIR/unconstrained-projection-normalization.rs:15:18
diff --git a/tests/ui/type-alias-impl-trait/ice-failed-to-resolve-instance-for-110696.stderr b/tests/ui/type-alias-impl-trait/ice-failed-to-resolve-instance-for-110696.stderr
@@ -3,6 +3,15 @@ error[E0207]: the type parameter `T` is not constrained by the impl trait, self
    |
 LL | impl<T: MyFrom<Phantom2<DummyT<U>>>, U> MyIndex<DummyT<T>> for Scope<U> {
    |      ^ unconstrained type parameter
+   |
+help: make use of the type parameter `T` in the `self` type
+   |
+LL | impl<T: MyFrom<Phantom2<DummyT<U>>>, U> MyIndex<DummyT<T>> for Scope<U, T> {
+   |                                                                       +++
+help: and add it to the struct definition of Scope as well since it's used in the body of the impl
+   |
+LL | struct Scope<T, T>(Phantom2<DummyT<T>>);
+   |               +++
 
 error: item does not constrain `DummyT::{opaque#0}`
   --> $DIR/ice-failed-to-resolve-instance-for-110696.rs:30:8
