Dont create object type when more than one principal is present

rust-lang · Nov 23, 2024 · 898ccdb · 898ccdb
1 parent ff1737b
commit 898ccdb
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Showing 9 changed files with 21 additions and 194 deletions.
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
@@ -92,11 +92,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) =
             expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
+
+        // We don't support >1 principal
         if regular_traits.len() > 1 {
-            let _ = self.report_trait_object_addition_traits_error(&regular_traits);
-        } else if regular_traits.is_empty() && auto_traits.is_empty() {
-            let reported = self.report_trait_object_with_no_traits_error(span, &trait_bounds);
-            return Ty::new_error(tcx, reported);
+            let guar = self.report_trait_object_addition_traits_error(&regular_traits);
+            return Ty::new_error(tcx, guar);
+        }
+        // We  don't support empty trait objects.
+        if regular_traits.is_empty() && auto_traits.is_empty() {
+            let guar = self.report_trait_object_with_no_traits_error(span, &trait_bounds);
+            return Ty::new_error(tcx, guar);
         }
 
         // Check that there are no gross dyn-compatibility violations;

diff --git a/tests/ui/associated-types/issue-22560.rs b/tests/ui/associated-types/issue-22560.rs
@@ -7,9 +7,6 @@ trait Sub<Rhs=Self> {
 }
 
 type Test = dyn Add + Sub;
-//~^ ERROR E0393
-//~| ERROR E0191
-//~| ERROR E0393
-//~| ERROR E0225
+//~^ ERROR E0225
 
 fn main() { }
diff --git a/tests/ui/associated-types/issue-22560.stderr b/tests/ui/associated-types/issue-22560.stderr
@@ -9,56 +9,6 @@ LL | type Test = dyn Add + Sub;
    = help: consider creating a new trait with all of these as supertraits and using that trait here instead: `trait NewTrait: Add + Sub {}`
    = note: auto-traits like `Send` and `Sync` are traits that have special properties; for more information on them, visit <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>
 
-error[E0191]: the value of the associated types `Output` in `Add`, `Output` in `Sub` must be specified
-  --> $DIR/issue-22560.rs:9:17
-   |
-LL |     type Output;
-   |     ----------- `Output` defined here
-...
-LL |     type Output;
-   |     ----------- `Output` defined here
-...
-LL | type Test = dyn Add + Sub;
-   |                 ^^^   ^^^ associated type `Output` must be specified
-   |                 |
-   |                 associated type `Output` must be specified
-   |
-help: specify the associated types
-   |
-LL | type Test = dyn Add<Output = Type> + Sub<Output = Type>;
-   |                 ~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~
-
-error[E0393]: the type parameter `Rhs` must be explicitly specified
-  --> $DIR/issue-22560.rs:9:17
-   |
-LL | trait Add<Rhs=Self> {
-   | ------------------- type parameter `Rhs` must be specified for this
-...
-LL | type Test = dyn Add + Sub;
-   |                 ^^^
-   |
-   = note: because of the default `Self` reference, type parameters must be specified on object types
-help: set the type parameter to the desired type
-   |
-LL | type Test = dyn Add<Rhs> + Sub;
-   |                    +++++
-
-error[E0393]: the type parameter `Rhs` must be explicitly specified
-  --> $DIR/issue-22560.rs:9:23
-   |
-LL | trait Sub<Rhs=Self> {
-   | ------------------- type parameter `Rhs` must be specified for this
-...
-LL | type Test = dyn Add + Sub;
-   |                       ^^^
-   |
-   = note: because of the default `Self` reference, type parameters must be specified on object types
-help: set the type parameter to the desired type
-   |
-LL | type Test = dyn Add + Sub<Rhs>;
-   |                          +++++
-
-error: aborting due to 4 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0191, E0225, E0393.
-For more information about an error, try `rustc --explain E0191`.
+For more information about this error, try `rustc --explain E0225`.
diff --git a/tests/ui/associated-types/missing-associated-types.rs b/tests/ui/associated-types/missing-associated-types.rs
@@ -11,16 +11,12 @@ trait Fine<Rhs>: Div<Rhs, Output = Rhs> {}
 
 type Foo<Rhs> = dyn Add<Rhs> + Sub<Rhs> + X<Rhs> + Y<Rhs>;
 //~^ ERROR only auto traits can be used as additional traits in a trait object
-//~| ERROR the value of the associated types
 type Bar<Rhs> = dyn Add<Rhs> + Sub<Rhs> + X<Rhs> + Z<Rhs>;
 //~^ ERROR only auto traits can be used as additional traits in a trait object
-//~| ERROR the value of the associated types
 type Baz<Rhs> = dyn Add<Rhs> + Sub<Rhs> + Y<Rhs>;
 //~^ ERROR only auto traits can be used as additional traits in a trait object
-//~| ERROR the value of the associated types
 type Bat<Rhs> = dyn Add<Rhs> + Sub<Rhs> + Fine<Rhs>;
 //~^ ERROR only auto traits can be used as additional traits in a trait object
-//~| ERROR the value of the associated types
 type Bal<Rhs> = dyn X<Rhs>;
 //~^ ERROR the value of the associated types
 

diff --git a/tests/ui/associated-types/missing-associated-types.stderr b/tests/ui/associated-types/missing-associated-types.stderr
@@ -9,26 +9,8 @@ LL | type Foo<Rhs> = dyn Add<Rhs> + Sub<Rhs> + X<Rhs> + Y<Rhs>;
    = help: consider creating a new trait with all of these as supertraits and using that trait here instead: `trait NewTrait: Add<Rhs> + Sub<Rhs> + X<Rhs> + Y<Rhs> {}`
    = note: auto-traits like `Send` and `Sync` are traits that have special properties; for more information on them, visit <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>
 
-error[E0191]: the value of the associated types `A` in `Y`, `Output` in `Add`, `Output` in `Mul`, `Output` in `Sub` must be specified
-  --> $DIR/missing-associated-types.rs:12:21
-   |
-LL |     type A;
-   |     ------ `A` defined here
-...
-LL | type Foo<Rhs> = dyn Add<Rhs> + Sub<Rhs> + X<Rhs> + Y<Rhs>;
-   |                     ^^^^^^^^   ^^^^^^^^   ^^^^^^   ^^^^^^ associated type `A` must be specified
-   |                     |          |          |
-   |                     |          |          associated type `Output` must be specified
-   |                     |          associated type `Output` must be specified
-   |                     associated type `Output` must be specified
-   |
-help: specify the associated types
-   |
-LL | type Foo<Rhs> = dyn Add<Rhs, Output = Type> + Sub<Rhs, Output = Type> + X<Rhs, Output = Type> + Y<Rhs, A = Type>;
-   |                     ~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~
-
 error[E0225]: only auto traits can be used as additional traits in a trait object
-  --> $DIR/missing-associated-types.rs:15:32
+  --> $DIR/missing-associated-types.rs:14:32
    |
 LL | type Bar<Rhs> = dyn Add<Rhs> + Sub<Rhs> + X<Rhs> + Z<Rhs>;
    |                     --------   ^^^^^^^^ additional non-auto trait
@@ -38,33 +20,8 @@ LL | type Bar<Rhs> = dyn Add<Rhs> + Sub<Rhs> + X<Rhs> + Z<Rhs>;
    = help: consider creating a new trait with all of these as supertraits and using that trait here instead: `trait NewTrait: Add<Rhs> + Sub<Rhs> + X<Rhs> + Z<Rhs> {}`
    = note: auto-traits like `Send` and `Sync` are traits that have special properties; for more information on them, visit <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>
 
-error[E0191]: the value of the associated types `A` and `B` in `Z`, `Output` and `Output` in `Div`, `Output` in `Add`, `Output` in `Mul`, `Output` in `Sub` must be specified
-  --> $DIR/missing-associated-types.rs:15:21
-   |
-LL |     type A;
-   |     ------ `A` defined here
-LL |     type B;
-   |     ------ `B` defined here
-...
-LL | type Bar<Rhs> = dyn Add<Rhs> + Sub<Rhs> + X<Rhs> + Z<Rhs>;
-   |                     ^^^^^^^^   ^^^^^^^^   ^^^^^^   ^^^^^^ associated types `A`, `B`, `Output` must be specified
-   |                     |          |          |
-   |                     |          |          associated types `Output` (from trait `Div`), `Output` (from trait `Mul`) must be specified
-   |                     |          associated type `Output` must be specified
-   |                     associated type `Output` must be specified
-   |
-help: consider introducing a new type parameter, adding `where` constraints using the fully-qualified path to the associated types
-  --> $DIR/missing-associated-types.rs:15:43
-   |
-LL | type Bar<Rhs> = dyn Add<Rhs> + Sub<Rhs> + X<Rhs> + Z<Rhs>;
-   |                                           ^^^^^^
-help: specify the associated types
-   |
-LL | type Bar<Rhs> = dyn Add<Rhs, Output = Type> + Sub<Rhs, Output = Type> + X<Rhs> + Z<Rhs, A = Type, B = Type, Output = Type>;
-   |                     ~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
 error[E0225]: only auto traits can be used as additional traits in a trait object
-  --> $DIR/missing-associated-types.rs:18:32
+  --> $DIR/missing-associated-types.rs:16:32
    |
 LL | type Baz<Rhs> = dyn Add<Rhs> + Sub<Rhs> + Y<Rhs>;
    |                     --------   ^^^^^^^^ additional non-auto trait
@@ -74,25 +31,8 @@ LL | type Baz<Rhs> = dyn Add<Rhs> + Sub<Rhs> + Y<Rhs>;
    = help: consider creating a new trait with all of these as supertraits and using that trait here instead: `trait NewTrait: Add<Rhs> + Sub<Rhs> + Y<Rhs> {}`
    = note: auto-traits like `Send` and `Sync` are traits that have special properties; for more information on them, visit <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>
 
-error[E0191]: the value of the associated types `A` in `Y`, `Output` in `Add`, `Output` in `Sub` must be specified
-  --> $DIR/missing-associated-types.rs:18:21
-   |
-LL |     type A;
-   |     ------ `A` defined here
-...
-LL | type Baz<Rhs> = dyn Add<Rhs> + Sub<Rhs> + Y<Rhs>;
-   |                     ^^^^^^^^   ^^^^^^^^   ^^^^^^ associated type `A` must be specified
-   |                     |          |
-   |                     |          associated type `Output` must be specified
-   |                     associated type `Output` must be specified
-   |
-help: specify the associated types
-   |
-LL | type Baz<Rhs> = dyn Add<Rhs, Output = Type> + Sub<Rhs, Output = Type> + Y<Rhs, A = Type>;
-   |                     ~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~
-
 error[E0225]: only auto traits can be used as additional traits in a trait object
-  --> $DIR/missing-associated-types.rs:21:32
+  --> $DIR/missing-associated-types.rs:18:32
    |
 LL | type Bat<Rhs> = dyn Add<Rhs> + Sub<Rhs> + Fine<Rhs>;
    |                     --------   ^^^^^^^^ additional non-auto trait
@@ -102,28 +42,15 @@ LL | type Bat<Rhs> = dyn Add<Rhs> + Sub<Rhs> + Fine<Rhs>;
    = help: consider creating a new trait with all of these as supertraits and using that trait here instead: `trait NewTrait: Add<Rhs> + Sub<Rhs> + Fine<Rhs> {}`
    = note: auto-traits like `Send` and `Sync` are traits that have special properties; for more information on them, visit <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>
 
-error[E0191]: the value of the associated types `Output` in `Add`, `Output` in `Sub` must be specified
-  --> $DIR/missing-associated-types.rs:21:21
-   |
-LL | type Bat<Rhs> = dyn Add<Rhs> + Sub<Rhs> + Fine<Rhs>;
-   |                     ^^^^^^^^   ^^^^^^^^ associated type `Output` must be specified
-   |                     |
-   |                     associated type `Output` must be specified
-   |
-help: specify the associated types
-   |
-LL | type Bat<Rhs> = dyn Add<Rhs, Output = Type> + Sub<Rhs, Output = Type> + Fine<Rhs>;
-   |                     ~~~~~~~~~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~
-
 error[E0191]: the value of the associated types `Output` in `Div`, `Output` in `Mul` must be specified
-  --> $DIR/missing-associated-types.rs:24:21
+  --> $DIR/missing-associated-types.rs:20:21
    |
 LL | type Bal<Rhs> = dyn X<Rhs>;
    |                     ^^^^^^ associated types `Output` (from trait `Div`), `Output` (from trait `Mul`) must be specified
    |
    = help: consider introducing a new type parameter, adding `where` constraints using the fully-qualified path to the associated types
 
-error: aborting due to 9 previous errors
+error: aborting due to 5 previous errors
 
 Some errors have detailed explanations: E0191, E0225.
 For more information about an error, try `rustc --explain E0191`.
diff --git a/tests/ui/traits/bad-sized.rs b/tests/ui/traits/bad-sized.rs
@@ -3,7 +3,4 @@ trait Trait {}
 pub fn main() {
     let x: Vec<dyn Trait + Sized> = Vec::new();
     //~^ ERROR only auto traits can be used as additional traits in a trait object
-    //~| ERROR the size for values of type
-    //~| ERROR the size for values of type
-    //~| ERROR the size for values of type
 }
diff --git a/tests/ui/traits/bad-sized.stderr b/tests/ui/traits/bad-sized.stderr
@@ -9,37 +9,6 @@ LL |     let x: Vec<dyn Trait + Sized> = Vec::new();
    = help: consider creating a new trait with all of these as supertraits and using that trait here instead: `trait NewTrait: Trait + Sized {}`
    = note: auto-traits like `Send` and `Sync` are traits that have special properties; for more information on them, visit <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>
 
-error[E0277]: the size for values of type `dyn Trait` cannot be known at compilation time
-  --> $DIR/bad-sized.rs:4:12
-   |
-LL |     let x: Vec<dyn Trait + Sized> = Vec::new();
-   |            ^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `dyn Trait`
-note: required by an implicit `Sized` bound in `Vec`
-  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
-
-error[E0277]: the size for values of type `dyn Trait` cannot be known at compilation time
-  --> $DIR/bad-sized.rs:4:37
-   |
-LL |     let x: Vec<dyn Trait + Sized> = Vec::new();
-   |                                     ^^^^^^^^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `dyn Trait`
-note: required by a bound in `Vec::<T>::new`
-  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
-
-error[E0277]: the size for values of type `dyn Trait` cannot be known at compilation time
-  --> $DIR/bad-sized.rs:4:37
-   |
-LL |     let x: Vec<dyn Trait + Sized> = Vec::new();
-   |                                     ^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `dyn Trait`
-note: required by an implicit `Sized` bound in `Vec`
-  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
-
-error: aborting due to 4 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0225, E0277.
-For more information about an error, try `rustc --explain E0225`.
+For more information about this error, try `rustc --explain E0225`.
diff --git a/tests/ui/traits/issue-32963.rs b/tests/ui/traits/issue-32963.rs
@@ -7,5 +7,4 @@ fn size_of_copy<T: Copy+?Sized>() -> usize { mem::size_of::<T>() }
 fn main() {
     size_of_copy::<dyn Misc + Copy>();
     //~^ ERROR only auto traits can be used as additional traits in a trait object
-    //~| ERROR the trait bound `dyn Misc: Copy` is not satisfied
 }
diff --git a/tests/ui/traits/issue-32963.stderr b/tests/ui/traits/issue-32963.stderr
@@ -9,19 +9,6 @@ LL |     size_of_copy::<dyn Misc + Copy>();
    = help: consider creating a new trait with all of these as supertraits and using that trait here instead: `trait NewTrait: Misc + Copy {}`
    = note: auto-traits like `Send` and `Sync` are traits that have special properties; for more information on them, visit <https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits>
 
-error[E0277]: the trait bound `dyn Misc: Copy` is not satisfied
-  --> $DIR/issue-32963.rs:8:20
-   |
-LL |     size_of_copy::<dyn Misc + Copy>();
-   |                    ^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `dyn Misc`
-   |
-note: required by a bound in `size_of_copy`
-  --> $DIR/issue-32963.rs:5:20
-   |
-LL | fn size_of_copy<T: Copy+?Sized>() -> usize { mem::size_of::<T>() }
-   |                    ^^^^ required by this bound in `size_of_copy`
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0225, E0277.
-For more information about an error, try `rustc --explain E0225`.
+For more information about this error, try `rustc --explain E0225`.