rust-lang · estebank · Aug 23, 2025
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -28,7 +28,7 @@ use rustc_middle::traits::IsConstable;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::print::{
     PrintPolyTraitPredicateExt as _, PrintPolyTraitRefExt, PrintTraitPredicateExt as _,
-    with_forced_trimmed_paths, with_no_trimmed_paths, with_types_for_suggestion,
+    with_crate_prefix, with_forced_trimmed_paths, with_no_trimmed_paths, with_types_for_suggestion,
 };
 use rustc_middle::ty::{
     self, AdtKind, GenericArgs, InferTy, IsSuggestable, Ty, TyCtxt, TypeFoldable, TypeFolder,
@@ -221,15 +221,24 @@ pub fn suggest_restriction<'tcx, G: EmissionGuarantee>(
             (_, None) => predicate_constraint(hir_generics, trait_pred.upcast(tcx)),
             (None, Some((ident, []))) => (
                 ident.span.shrink_to_hi(),
-                format!(": {}", trait_pred.print_modifiers_and_trait_path()),
+                with_crate_prefix!(with_no_trimmed_paths!(format!(
+                    ": {}",
+                    trait_pred.print_modifiers_and_trait_path()
+                ))),
             ),
             (_, Some((_, [.., bounds]))) => (
                 bounds.span().shrink_to_hi(),
-                format!(" + {}", trait_pred.print_modifiers_and_trait_path()),
+                with_crate_prefix!(with_no_trimmed_paths!(format!(
+                    " + {}",
+                    trait_pred.print_modifiers_and_trait_path()
+                ))),
             ),
             (Some(_), Some((_, []))) => (
                 hir_generics.span.shrink_to_hi(),
-                format!(": {}", trait_pred.print_modifiers_and_trait_path()),
+                with_crate_prefix!(with_no_trimmed_paths!(format!(
+                    ": {}",
+                    trait_pred.print_modifiers_and_trait_path()
+                ))),
             ),
         };
 
@@ -384,9 +393,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     }
                     // Missing generic type parameter bound.
                     let param_name = self_ty.to_string();
-                    let mut constraint = with_no_trimmed_paths!(
-                        trait_pred.print_modifiers_and_trait_path().to_string()
-                    );
+                    let mut constraint = with_crate_prefix!(with_no_trimmed_paths!(format!(
+                        "{}",
+                        trait_pred.print_modifiers_and_trait_path()
+                    )));
 
                     if let Some((name, term)) = associated_ty {
                         // FIXME: this case overlaps with code in TyCtxt::note_and_explain_type_err.

diff --git a/tests/ui/associated-types/defaults-unsound-62211-1.current.stderr b/tests/ui/associated-types/defaults-unsound-62211-1.current.stderr
@@ -27,8 +27,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + AddAssign<&'static str> {
-   |                            +++++++++++++++++++++++++
+LL | trait UncheckedCopy: Sized + std::ops::AddAssign<&'static str> {
+   |                            +++++++++++++++++++++++++++++++++++
 
 error[E0277]: the trait bound `Self: Deref` is not satisfied
   --> $DIR/defaults-unsound-62211-1.rs:24:96
@@ -43,8 +43,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                         ^^^^^^^^^^^^^^^^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + Deref {
-   |                            +++++++
+LL | trait UncheckedCopy: Sized + std::ops::Deref {
+   |                            +++++++++++++++++
 
 error[E0277]: the trait bound `Self: Copy` is not satisfied
   --> $DIR/defaults-unsound-62211-1.rs:24:96
@@ -59,8 +59,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                  ^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + Copy {
-   |                            ++++++
+LL | trait UncheckedCopy: Sized + std::marker::Copy {
+   |                            +++++++++++++++++++
 
 error: aborting due to 4 previous errors
 

diff --git a/tests/ui/associated-types/defaults-unsound-62211-1.next.stderr b/tests/ui/associated-types/defaults-unsound-62211-1.next.stderr
@@ -27,8 +27,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + AddAssign<&'static str> {
-   |                            +++++++++++++++++++++++++
+LL | trait UncheckedCopy: Sized + std::ops::AddAssign<&'static str> {
+   |                            +++++++++++++++++++++++++++++++++++
 
 error[E0277]: the trait bound `Self: Deref` is not satisfied
   --> $DIR/defaults-unsound-62211-1.rs:24:96
@@ -43,8 +43,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                               ^^^^^^^^^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + Deref {
-   |                            +++++++
+LL | trait UncheckedCopy: Sized + std::ops::Deref {
+   |                            +++++++++++++++++
 
 error[E0277]: the trait bound `Self: Copy` is not satisfied
   --> $DIR/defaults-unsound-62211-1.rs:24:96
@@ -59,8 +59,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                  ^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + Copy {
-   |                            ++++++
+LL | trait UncheckedCopy: Sized + std::marker::Copy {
+   |                            +++++++++++++++++++
 
 error: aborting due to 4 previous errors
 

diff --git a/tests/ui/associated-types/defaults-unsound-62211-2.current.stderr b/tests/ui/associated-types/defaults-unsound-62211-2.current.stderr
@@ -27,8 +27,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + AddAssign<&'static str> {
-   |                            +++++++++++++++++++++++++
+LL | trait UncheckedCopy: Sized + std::ops::AddAssign<&'static str> {
+   |                            +++++++++++++++++++++++++++++++++++
 
 error[E0277]: the trait bound `Self: Deref` is not satisfied
   --> $DIR/defaults-unsound-62211-2.rs:24:96
@@ -43,8 +43,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                         ^^^^^^^^^^^^^^^^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + Deref {
-   |                            +++++++
+LL | trait UncheckedCopy: Sized + std::ops::Deref {
+   |                            +++++++++++++++++
 
 error[E0277]: the trait bound `Self: Copy` is not satisfied
   --> $DIR/defaults-unsound-62211-2.rs:24:96
@@ -59,8 +59,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                  ^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + Copy {
-   |                            ++++++
+LL | trait UncheckedCopy: Sized + std::marker::Copy {
+   |                            +++++++++++++++++++
 
 error: aborting due to 4 previous errors
 

diff --git a/tests/ui/associated-types/defaults-unsound-62211-2.next.stderr b/tests/ui/associated-types/defaults-unsound-62211-2.next.stderr
@@ -27,8 +27,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + AddAssign<&'static str> {
-   |                            +++++++++++++++++++++++++
+LL | trait UncheckedCopy: Sized + std::ops::AddAssign<&'static str> {
+   |                            +++++++++++++++++++++++++++++++++++
 
 error[E0277]: the trait bound `Self: Deref` is not satisfied
   --> $DIR/defaults-unsound-62211-2.rs:24:96
@@ -43,8 +43,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                               ^^^^^^^^^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + Deref {
-   |                            +++++++
+LL | trait UncheckedCopy: Sized + std::ops::Deref {
+   |                            +++++++++++++++++
 
 error[E0277]: the trait bound `Self: Copy` is not satisfied
   --> $DIR/defaults-unsound-62211-2.rs:24:96
@@ -59,8 +59,8 @@ LL |     type Output: Copy + Deref<Target = str> + AddAssign<&'static str> + Fro
    |                  ^^^^ required by this bound in `UncheckedCopy::Output`
 help: consider further restricting `Self`
    |
-LL | trait UncheckedCopy: Sized + Copy {
-   |                            ++++++
+LL | trait UncheckedCopy: Sized + std::marker::Copy {
+   |                            +++++++++++++++++++
 
 error: aborting due to 4 previous errors
 

diff --git a/tests/ui/associated-types/issue-63593.current.stderr b/tests/ui/associated-types/issue-63593.current.stderr
@@ -11,8 +11,8 @@ LL |     type This = Self;
    |     ^^^^^^^^^^^^^^^^^ required by this bound in `MyTrait::This`
 help: consider further restricting `Self`
    |
-LL | trait MyTrait: Sized {
-   |              +++++++
+LL | trait MyTrait: std::marker::Sized {
+   |              ++++++++++++++++++++
 
 error: aborting due to 1 previous error
 

diff --git a/tests/ui/associated-types/issue-63593.next.stderr b/tests/ui/associated-types/issue-63593.next.stderr
@@ -11,8 +11,8 @@ LL |     type This = Self;
    |     ^^^^^^^^^^^^^^^^^ required by this bound in `MyTrait::This`
 help: consider further restricting `Self`
    |
-LL | trait MyTrait: Sized {
-   |              +++++++
+LL | trait MyTrait: std::marker::Sized {
+   |              ++++++++++++++++++++
 
 error: aborting due to 1 previous error
 

diff --git a/tests/ui/associated-types/trait-with-supertraits-needing-sized-self.stderr b/tests/ui/associated-types/trait-with-supertraits-needing-sized-self.stderr
@@ -8,8 +8,8 @@ note: required by an implicit `Sized` bound in `Add`
   --> $SRC_DIR/core/src/ops/arith.rs:LL:COL
 help: consider further restricting `Self`
    |
-LL | trait ArithmeticOps: Add<Output=Self> + Sub<Output=Self> + Mul<Output=Self> + Div<Output=Self> + Sized {}
-   |                                                                                                +++++++
+LL | trait ArithmeticOps: Add<Output=Self> + Sub<Output=Self> + Mul<Output=Self> + Div<Output=Self> + std::marker::Sized {}
+   |                                                                                                ++++++++++++++++++++
 
 error: aborting due to 1 previous error
 

diff --git a/tests/ui/dyn-compatibility/supertrait-mentions-Self.stderr b/tests/ui/dyn-compatibility/supertrait-mentions-Self.stderr
@@ -11,8 +11,8 @@ LL | trait Bar<T> {
    |           ^ required by the implicit `Sized` requirement on this type parameter in `Bar`
 help: consider further restricting `Self`
    |
-LL | trait Baz : Bar<Self> + Sized {
-   |                       +++++++
+LL | trait Baz : Bar<Self> + std::marker::Sized {
+   |                       ++++++++++++++++++++
 help: consider relaxing the implicit `Sized` restriction
    |
 LL | trait Bar<T: ?Sized> {

diff --git a/tests/ui/generic-associated-types/issue-74816.current.stderr b/tests/ui/generic-associated-types/issue-74816.current.stderr
@@ -27,8 +27,8 @@ LL |     type Associated: Trait1 = Self;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Trait2::Associated`
 help: consider further restricting `Self`
    |
-LL | trait Trait2: Sized {
-   |             +++++++
+LL | trait Trait2: std::marker::Sized {
+   |             ++++++++++++++++++++
 
 error: aborting due to 2 previous errors
 

diff --git a/tests/ui/generic-associated-types/issue-74816.next.stderr b/tests/ui/generic-associated-types/issue-74816.next.stderr
@@ -27,8 +27,8 @@ LL |     type Associated: Trait1 = Self;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Trait2::Associated`
 help: consider further restricting `Self`
    |
-LL | trait Trait2: Sized {
-   |             +++++++
+LL | trait Trait2: std::marker::Sized {
+   |             ++++++++++++++++++++
 
 error: aborting due to 2 previous errors
 

diff --git a/tests/ui/suggestions/bound-suggestions.fixed b/tests/ui/suggestions/bound-suggestions.fixed
@@ -1,73 +1,75 @@
 //@ run-rustfix
+//@ edition:2018
+
+#![allow(unused)]
 
-#[allow(unused)]
 use std::fmt::Debug;
 // Rustfix should add this, or use `std::fmt::Debug` instead.
 
-#[allow(dead_code)]
 fn test_impl(t: impl Sized + std::fmt::Debug) {
     println!("{:?}", t);
     //~^ ERROR doesn't implement
 }
 
-#[allow(dead_code)]
 fn test_no_bounds<T: std::fmt::Debug>(t: T) {
     println!("{:?}", t);
     //~^ ERROR doesn't implement
 }
 
-#[allow(dead_code)]
 fn test_one_bound<T: Sized + std::fmt::Debug>(t: T) {
     println!("{:?}", t);
     //~^ ERROR doesn't implement
 }
 
-#[allow(dead_code)]
 fn test_no_bounds_where<X, Y>(x: X, y: Y) where X: std::fmt::Debug, Y: std::fmt::Debug {
     println!("{:?} {:?}", x, y);
     //~^ ERROR doesn't implement
 }
 
-#[allow(dead_code)]
 fn test_one_bound_where<X>(x: X) where X: Sized + std::fmt::Debug {
     println!("{:?}", x);
     //~^ ERROR doesn't implement
 }
 
-#[allow(dead_code)]
 fn test_many_bounds_where<X>(x: X) where X: Sized + std::fmt::Debug, X: Sized {
     println!("{:?}", x);
     //~^ ERROR doesn't implement
 }
 
-#[allow(dead_code)]
-trait Foo<T>: Sized {
+trait Foo<T>: std::marker::Sized {
     const SIZE: usize = core::mem::size_of::<Self>();
     //~^ ERROR the size for values of type `Self` cannot be known at compilation time
 }
 
-#[allow(dead_code)]
-trait Bar: std::fmt::Display + Sized {
+trait Bar: std::fmt::Display + std::marker::Sized {
     const SIZE: usize = core::mem::size_of::<Self>();
     //~^ ERROR the size for values of type `Self` cannot be known at compilation time
 }
 
-#[allow(dead_code)]
-trait Baz: Sized where Self: std::fmt::Display {
+trait Baz: std::marker::Sized where Self: std::fmt::Display {
     const SIZE: usize = core::mem::size_of::<Self>();
     //~^ ERROR the size for values of type `Self` cannot be known at compilation time
 }
 
-#[allow(dead_code)]
-trait Qux<T>: Sized where Self: std::fmt::Display {
+trait Qux<T>: std::marker::Sized where Self: std::fmt::Display {
     const SIZE: usize = core::mem::size_of::<Self>();
     //~^ ERROR the size for values of type `Self` cannot be known at compilation time
 }
 
-#[allow(dead_code)]
-trait Bat<T>: std::fmt::Display + Sized {
+trait Bat<T>: std::fmt::Display + std::marker::Sized {
     const SIZE: usize = core::mem::size_of::<Self>();
     //~^ ERROR the size for values of type `Self` cannot be known at compilation time
 }
 
+trait MyTrait {}
+
+trait Wrapper<T: MyTrait> {}
+
+mod inner {
+    trait MyTrait {}
+    // Ensure that we suggest the fully-qualified path of `crate::MyTrait`
+    // We only do that on editions>=2018.
+    fn method<T: MyTrait + crate::MyTrait, W: super::Wrapper<T>>() {} //~ ERROR the trait bound `T: MyTrait` is not satisfied
+}
+
 fn main() { }