Reword diagnostics about relaxed bounds in invalid contexts

fmease · fmease · commit d8ab552ac78c · 2025-07-02T02:18:55.000+02:00
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
@@ -2085,11 +2085,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                 match reason {
                     RelaxedBoundForbiddenReason::TraitObjectTy => {
-                        err("`?Trait` is not permitted in trait object types").emit();
+                        err("relaxed bounds are not permitted in trait object types").emit();
                         return;
                     }
                     RelaxedBoundForbiddenReason::SuperTrait => {
-                        let mut diag = err("`?Trait` is not permitted in supertraits");
+                        let mut diag = err("relaxed bounds are not permitted in supertrait bounds");
                         if let Some(def_id) = trait_ref.trait_def_id()
                             && self.tcx.is_lang_item(def_id, hir::LangItem::Sized)
                         {
@@ -2103,7 +2103,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             }
         }
 
-        err("`?Trait` bounds are only permitted at the point where a type parameter is declared")
+        err("this relaxed bound is not permitted here")
+            .with_note(
+                "in this context, relaxed bounds are only allowed on \
+                 type parameters defined by the closest item",
+            )
             .emit();
     }
 
diff --git a/tests/ui/associated-item/missing-associated_item_or_field_def_ids.rs b/tests/ui/associated-item/missing-associated_item_or_field_def_ids.rs
@@ -2,6 +2,6 @@
 
 fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
     //~^ ERROR expected trait, found associated function `Iterator::advance_by`
-    //~| ERROR `?Trait` is not permitted in trait object types
+    //~| ERROR relaxed bounds are not permitted in trait object types
     todo!()
 }
diff --git a/tests/ui/associated-item/missing-associated_item_or_field_def_ids.stderr b/tests/ui/associated-item/missing-associated_item_or_field_def_ids.stderr
@@ -4,7 +4,7 @@ error[E0404]: expected trait, found associated function `Iterator::advance_by`
 LL | fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a trait
 
-error[E0658]: `?Trait` is not permitted in trait object types
+error[E0658]: relaxed bounds are not permitted in trait object types
   --> $DIR/missing-associated_item_or_field_def_ids.rs:3:29
    |
 LL | fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {
diff --git a/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.rs b/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.rs
@@ -7,5 +7,5 @@ trait Tr {
 fn main() {
     let _: dyn Tr + ?Foo<Assoc = ()>;
     //~^ ERROR: cannot find trait `Foo` in this scope
-    //~| ERROR: `?Trait` is not permitted in trait object types
+    //~| ERROR: relaxed bounds are not permitted in trait object types
 }
diff --git a/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.stderr b/tests/ui/associated-types/avoid-getting-associated-items-of-undefined-trait.stderr
@@ -4,7 +4,7 @@ error[E0405]: cannot find trait `Foo` in this scope
 LL |     let _: dyn Tr + ?Foo<Assoc = ()>;
    |                      ^^^ not found in this scope
 
-error[E0658]: `?Trait` is not permitted in trait object types
+error[E0658]: relaxed bounds are not permitted in trait object types
   --> $DIR/avoid-getting-associated-items-of-undefined-trait.rs:8:21
    |
 LL |     let _: dyn Tr + ?Foo<Assoc = ()>;
diff --git a/tests/ui/feature-gates/feature-gate-more-maybe-bounds.rs b/tests/ui/feature-gates/feature-gate-more-maybe-bounds.rs
@@ -2,13 +2,11 @@
 
 trait Trait1 {}
 auto trait Trait2 {}
-trait Trait3: ?Trait1 {}
-//~^  ERROR `?Trait` is not permitted in supertraits
-trait Trait4 where Self: ?Trait1 {}
-//~^ ERROR ?Trait` bounds are only permitted at the point where a type parameter is declared
+trait Trait3: ?Trait1 {} //~ ERROR relaxed bounds are not permitted in supertrait bounds
+trait Trait4 where Self: ?Trait1 {} //~ ERROR this relaxed bound is not permitted here
 
 fn foo(_: Box<dyn Trait1 + ?Trait2>) {}
-//~^  ERROR `?Trait` is not permitted in trait object types
+//~^  ERROR relaxed bounds are not permitted in trait object types
 fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
 //~^ ERROR type parameter has more than one relaxed default bound, only one is supported
 //~| ERROR relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
diff --git a/tests/ui/feature-gates/feature-gate-more-maybe-bounds.stderr b/tests/ui/feature-gates/feature-gate-more-maybe-bounds.stderr
@@ -1,4 +1,4 @@
-error[E0658]: `?Trait` is not permitted in supertraits
+error[E0658]: relaxed bounds are not permitted in supertrait bounds
   --> $DIR/feature-gate-more-maybe-bounds.rs:5:15
    |
 LL | trait Trait3: ?Trait1 {}
@@ -7,17 +7,18 @@ LL | trait Trait3: ?Trait1 {}
    = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error[E0658]: `?Trait` bounds are only permitted at the point where a type parameter is declared
-  --> $DIR/feature-gate-more-maybe-bounds.rs:7:26
+error[E0658]: this relaxed bound is not permitted here
+  --> $DIR/feature-gate-more-maybe-bounds.rs:6:26
    |
 LL | trait Trait4 where Self: ?Trait1 {}
    |                          ^^^^^^^
    |
    = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: in this context, relaxed bounds are only allowed on type parameters defined by the closest item
 
-error[E0658]: `?Trait` is not permitted in trait object types
-  --> $DIR/feature-gate-more-maybe-bounds.rs:10:28
+error[E0658]: relaxed bounds are not permitted in trait object types
+  --> $DIR/feature-gate-more-maybe-bounds.rs:8:28
    |
 LL | fn foo(_: Box<dyn Trait1 + ?Trait2>) {}
    |                            ^^^^^^^
@@ -26,7 +27,7 @@ LL | fn foo(_: Box<dyn Trait1 + ?Trait2>) {}
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0203]: type parameter has more than one relaxed default bound, only one is supported
-  --> $DIR/feature-gate-more-maybe-bounds.rs:12:11
+  --> $DIR/feature-gate-more-maybe-bounds.rs:10:11
    |
 LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
    |           ^^^^^^^   ^^^^^^^
@@ -35,31 +36,31 @@ LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/feature-gate-more-maybe-bounds.rs:12:11
+  --> $DIR/feature-gate-more-maybe-bounds.rs:10:11
    |
 LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
    |           ^^^^^^^
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/feature-gate-more-maybe-bounds.rs:12:21
+  --> $DIR/feature-gate-more-maybe-bounds.rs:10:21
    |
 LL | fn bar<T: ?Trait1 + ?Trait2>(_: T) {}
    |                     ^^^^^^^
 
 error[E0203]: type parameter has more than one relaxed default bound, only one is supported
-  --> $DIR/feature-gate-more-maybe-bounds.rs:19:11
+  --> $DIR/feature-gate-more-maybe-bounds.rs:17:11
    |
 LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
    |           ^^^^^^   ^^^^^^
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/feature-gate-more-maybe-bounds.rs:19:11
+  --> $DIR/feature-gate-more-maybe-bounds.rs:17:11
    |
 LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
    |           ^^^^^^
 
 error: relaxing a default bound only does something for `?Sized`; all other traits are not bound by default
-  --> $DIR/feature-gate-more-maybe-bounds.rs:19:20
+  --> $DIR/feature-gate-more-maybe-bounds.rs:17:20
    |
 LL | fn baz<T: ?Trait + ?Trait>(_ : T) {}
    |                    ^^^^^^
diff --git a/tests/ui/parser/trait-object-trait-parens.rs b/tests/ui/parser/trait-object-trait-parens.rs
@@ -6,17 +6,17 @@ fn f<T: (Copy) + (?Sized) + (for<'a> Trait<'a>)>() {}
 
 fn main() {
     let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
-    //~^ ERROR `?Trait` is not permitted in trait object types
+    //~^ ERROR relaxed bounds are not permitted in trait object types
     //~| ERROR only auto traits can be used as additional traits
     //~| WARN trait objects without an explicit `dyn` are deprecated
     //~| WARN this is accepted in the current edition
     let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>;
-    //~^ ERROR `?Trait` is not permitted in trait object types
+    //~^ ERROR relaxed bounds are not permitted in trait object types
     //~| ERROR only auto traits can be used as additional traits
     //~| WARN trait objects without an explicit `dyn` are deprecated
     //~| WARN this is accepted in the current edition
     let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>;
-    //~^ ERROR `?Trait` is not permitted in trait object types
+    //~^ ERROR relaxed bounds are not permitted in trait object types
     //~| ERROR only auto traits can be used as additional traits
     //~| WARN trait objects without an explicit `dyn` are deprecated
     //~| WARN this is accepted in the current edition
diff --git a/tests/ui/parser/trait-object-trait-parens.stderr b/tests/ui/parser/trait-object-trait-parens.stderr
@@ -1,4 +1,4 @@
-error[E0658]: `?Trait` is not permitted in trait object types
+error[E0658]: relaxed bounds are not permitted in trait object types
   --> $DIR/trait-object-trait-parens.rs:8:24
    |
 LL |     let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
@@ -7,7 +7,7 @@ LL |     let _: Box<(Obj) + (?Sized) + (for<'a> Trait<'a>)>;
    = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error[E0658]: `?Trait` is not permitted in trait object types
+error[E0658]: relaxed bounds are not permitted in trait object types
   --> $DIR/trait-object-trait-parens.rs:13:16
    |
 LL |     let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>;
@@ -16,7 +16,7 @@ LL |     let _: Box<?Sized + (for<'a> Trait<'a>) + (Obj)>;
    = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error[E0658]: `?Trait` is not permitted in trait object types
+error[E0658]: relaxed bounds are not permitted in trait object types
   --> $DIR/trait-object-trait-parens.rs:18:44
    |
 LL |     let _: Box<for<'a> Trait<'a> + (Obj) + (?Sized)>;
diff --git a/tests/ui/sized-hierarchy/default-supertrait.rs b/tests/ui/sized-hierarchy/default-supertrait.rs
@@ -6,18 +6,18 @@ use std::marker::{MetaSized, PointeeSized};
 trait Sized_: Sized { }
 
 trait NegSized: ?Sized { }
-//~^ ERROR `?Trait` is not permitted in supertraits
+//~^ ERROR relaxed bounds are not permitted in supertrait bounds
 
 trait MetaSized_: MetaSized { }
 
 trait NegMetaSized: ?MetaSized { }
-//~^ ERROR `?Trait` is not permitted in supertraits
+//~^ ERROR relaxed bounds are not permitted in supertrait bounds
 
 
 trait PointeeSized_: PointeeSized { }
 
 trait NegPointeeSized: ?PointeeSized { }
-//~^ ERROR `?Trait` is not permitted in supertraits
+//~^ ERROR relaxed bounds are not permitted in supertrait bounds
 
 trait Bare {}
 
diff --git a/tests/ui/sized-hierarchy/default-supertrait.stderr b/tests/ui/sized-hierarchy/default-supertrait.stderr
@@ -1,4 +1,4 @@
-error[E0658]: `?Trait` is not permitted in supertraits
+error[E0658]: relaxed bounds are not permitted in supertrait bounds
   --> $DIR/default-supertrait.rs:8:17
    |
 LL | trait NegSized: ?Sized { }
@@ -8,7 +8,7 @@ LL | trait NegSized: ?Sized { }
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
    = note: traits are `?Sized` by default
 
-error[E0658]: `?Trait` is not permitted in supertraits
+error[E0658]: relaxed bounds are not permitted in supertrait bounds
   --> $DIR/default-supertrait.rs:13:21
    |
 LL | trait NegMetaSized: ?MetaSized { }
@@ -17,7 +17,7 @@ LL | trait NegMetaSized: ?MetaSized { }
    = help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error[E0658]: `?Trait` is not permitted in supertraits
+error[E0658]: relaxed bounds are not permitted in supertrait bounds
   --> $DIR/default-supertrait.rs:19:24
    |
 LL | trait NegPointeeSized: ?PointeeSized { }
diff --git a/tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs b/tests/ui/traits/maybe-trait-bounds-forbidden-locations.rs
diff --git a/tests/ui/traits/maybe-trait-bounds-forbidden-locations.stderr b/tests/ui/traits/maybe-trait-bounds-forbidden-locations.stderr
diff --git a/tests/ui/traits/wf-object/maybe-bound.rs b/tests/ui/traits/wf-object/maybe-bound.rs
diff --git a/tests/ui/traits/wf-object/maybe-bound.stderr b/tests/ui/traits/wf-object/maybe-bound.stderr
diff --git a/tests/ui/traits/wf-object/only-maybe-bound.rs b/tests/ui/traits/wf-object/only-maybe-bound.rs
@@ -2,6 +2,6 @@
 
 type _0 = dyn ?Sized;
 //~^ ERROR at least one trait is required for an object type [E0224]
-//~| ERROR ?Trait` is not permitted in trait object types
+//~| ERROR relaxed bounds are not permitted in trait object types
 
 fn main() {}
diff --git a/tests/ui/traits/wf-object/only-maybe-bound.stderr b/tests/ui/traits/wf-object/only-maybe-bound.stderr
@@ -1,4 +1,4 @@
-error[E0658]: `?Trait` is not permitted in trait object types
+error[E0658]: relaxed bounds are not permitted in trait object types
   --> $DIR/only-maybe-bound.rs:3:15
    |
 LL | type _0 = dyn ?Sized;
diff --git a/tests/ui/unsized/relaxed-bounds-invalid-places.rs b/tests/ui/unsized/relaxed-bounds-invalid-places.rs
diff --git a/tests/ui/unsized/relaxed-bounds-invalid-places.stderr b/tests/ui/unsized/relaxed-bounds-invalid-places.stderr

Original file line number	Diff line number	Diff line change
`@@ -2085,11 +2085,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {`
`2085`	`2085`
`2086`	`2086`	`match reason {`
`2087`	`2087`	`RelaxedBoundForbiddenReason::TraitObjectTy => {`
`2088`		- err("`?Trait` is not permitted in trait object types").emit();
	`2088`	`+ err("relaxed bounds are not permitted in trait object types").emit();`
`2089`	`2089`	`return;`
`2090`	`2090`	`}`
`2091`	`2091`	`RelaxedBoundForbiddenReason::SuperTrait => {`
`2092`		- let mut diag = err("`?Trait` is not permitted in supertraits");
	`2092`	`+ let mut diag = err("relaxed bounds are not permitted in supertrait bounds");`
`2093`	`2093`	`if let Some(def_id) = trait_ref.trait_def_id()`
`2094`	`2094`	`&& self.tcx.is_lang_item(def_id, hir::LangItem::Sized)`
`2095`	`2095`	`{`
`@@ -2103,7 +2103,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {`
`2103`	`2103`	`}`
`2104`	`2104`	`}`
`2105`	`2105`
`2106`		- err("`?Trait` bounds are only permitted at the point where a type parameter is declared")
	`2106`	`+ err("this relaxed bound is not permitted here")`
	`2107`	`+ .with_note(`
	`2108`	`+ "in this context, relaxed bounds are only allowed on \`
	`2109`	`+ type parameters defined by the closest item",`
	`2110`	`+ )`
`2107`	`2111`	`.emit();`
`2108`	`2112`	`}`
`2109`	`2113`
Original file line number	Diff line number	Diff line change
`@@ -2,6 +2,6 @@`
`2`	`2`
`3`	`3`	`fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {`
`4`	`4`	//~^ ERROR expected trait, found associated function `Iterator::advance_by`
`5`		- //~\| ERROR `?Trait` is not permitted in trait object types
	`5`	`+ //~\| ERROR relaxed bounds are not permitted in trait object types`
`6`	`6`	`todo!()`
`7`	`7`	`}`
Original file line number	Diff line number	Diff line change
@@ -4,7 +4,7 @@ error[E0404]: expected trait, found associated function `Iterator::advance_by`
`4`	`4`	`LL \| fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {`
`5`	`5`	`\| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a trait`
`6`	`6`
`7`		-error[E0658]: `?Trait` is not permitted in trait object types
	`7`	`+error[E0658]: relaxed bounds are not permitted in trait object types`
`8`	`8`	`--> $DIR/missing-associated_item_or_field_def_ids.rs:3:29`
`9`	`9`	`\|`
`10`	`10`	`LL \| fn main() -> dyn Iterator + ?Iterator::advance_by(usize) {`
Original file line number	Diff line number	Diff line change
`@@ -7,5 +7,5 @@ trait Tr {`
`7`	`7`	`fn main() {`
`8`	`8`	`let _: dyn Tr + ?Foo<Assoc = ()>;`
`9`	`9`	//~^ ERROR: cannot find trait `Foo` in this scope
`10`		- //~\| ERROR: `?Trait` is not permitted in trait object types
	`10`	`+ //~\| ERROR: relaxed bounds are not permitted in trait object types`
`11`	`11`	`}`
Original file line number	Diff line number	Diff line change
@@ -4,7 +4,7 @@ error[E0405]: cannot find trait `Foo` in this scope
`4`	`4`	`LL \| let _: dyn Tr + ?Foo<Assoc = ()>;`
`5`	`5`	`\| ^^^ not found in this scope`
`6`	`6`
`7`		-error[E0658]: `?Trait` is not permitted in trait object types
	`7`	`+error[E0658]: relaxed bounds are not permitted in trait object types`
`8`	`8`	`--> $DIR/avoid-getting-associated-items-of-undefined-trait.rs:8:21`
`9`	`9`	`\|`
`10`	`10`	`LL \| let _: dyn Tr + ?Foo<Assoc = ()>;`
Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		-error[E0658]: `?Trait` is not permitted in trait object types
	`1`	`+error[E0658]: relaxed bounds are not permitted in trait object types`
`2`	`2`	`--> $DIR/only-maybe-bound.rs:3:15`
`3`	`3`	`\|`
`4`	`4`	`LL \| type _0 = dyn ?Sized;`