diff options
4 files changed, 92 insertions, 2 deletions
diff --git a/src/test/ui/traits/trait-object-with-self-in-projection-output-bad.rs b/src/test/ui/traits/trait-object-with-self-in-projection-output-bad.rs index b157ef6ed5d..766bd147431 100644 --- a/src/test/ui/traits/trait-object-with-self-in-projection-output-bad.rs +++ b/src/test/ui/traits/trait-object-with-self-in-projection-output-bad.rs @@ -1,3 +1,7 @@ +// Regression test for #56288. Checks that if a supertrait defines an associated type +// projection that references `Self`, then that associated type must still be explicitly +// specified in the `dyn Trait` variant, since we don't know what `Self` is anymore. + trait Base { type Output; } @@ -16,7 +20,31 @@ impl Helper for u32 type Target = i32; } +trait ConstI32 { + type Out; +} + +impl<T: ?Sized> ConstI32 for T { + type Out = i32; +} + +// Test that you still need to manually give a projection type if the Output type +// is normalizable. +trait NormalizableHelper: + Base<Output=<Self as ConstI32>::Out> +{ + type Target; +} + +impl NormalizableHelper for u32 +{ + type Target = i32; +} + fn main() { let _x: Box<dyn Helper<Target=i32>> = Box::new(2u32); //~^ ERROR the value of the associated type `Output` (from the trait `Base`) must be specified + + let _y: Box<dyn NormalizableHelper<Target=i32>> = Box::new(2u32); + //~^ ERROR the value of the associated type `Output` (from the trait `Base`) must be specified } diff --git a/src/test/ui/traits/trait-object-with-self-in-projection-output-bad.stderr b/src/test/ui/traits/trait-object-with-self-in-projection-output-bad.stderr index c2e274b0245..350f8ea8507 100644 --- a/src/test/ui/traits/trait-object-with-self-in-projection-output-bad.stderr +++ b/src/test/ui/traits/trait-object-with-self-in-projection-output-bad.stderr @@ -1,5 +1,5 @@ error[E0191]: the value of the associated type `Output` (from the trait `Base`) must be specified - --> $DIR/trait-object-with-self-in-projection-output-bad.rs:20:17 + --> $DIR/trait-object-with-self-in-projection-output-bad.rs:45:17 | LL | type Output; | ------------ `Output` defined here @@ -7,6 +7,15 @@ LL | type Output; LL | let _x: Box<dyn Helper<Target=i32>> = Box::new(2u32); | ^^^^^^^^^^^^^^^^^^^^^^ associated type `Output` must be specified -error: aborting due to previous error +error[E0191]: the value of the associated type `Output` (from the trait `Base`) must be specified + --> $DIR/trait-object-with-self-in-projection-output-bad.rs:48:17 + | +LL | type Output; + | ------------ `Output` defined here +... +LL | let _y: Box<dyn NormalizableHelper<Target=i32>> = Box::new(2u32); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ associated type `Output` must be specified + +error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0191`. diff --git a/src/test/ui/traits/trait-object-with-self-in-projection-output-good.rs b/src/test/ui/traits/trait-object-with-self-in-projection-output-good.rs index 07681086e16..793d556d08c 100644 --- a/src/test/ui/traits/trait-object-with-self-in-projection-output-good.rs +++ b/src/test/ui/traits/trait-object-with-self-in-projection-output-good.rs @@ -1,5 +1,10 @@ // compile-pass +// Regression test related to #56288. Check that a supertrait projection (of +// `Output`) that references `Self` can be ok if it is referencing a projection (of +// `Self::Target`, in this case). Note that we still require the user to manually +// specify both `Target` and `Output` for now. + trait Base { type Output; } diff --git a/src/test/ui/traits/trait-object-with-self-in-projection-output-repeated-supertrait.rs b/src/test/ui/traits/trait-object-with-self-in-projection-output-repeated-supertrait.rs new file mode 100644 index 00000000000..46c083f9305 --- /dev/null +++ b/src/test/ui/traits/trait-object-with-self-in-projection-output-repeated-supertrait.rs @@ -0,0 +1,48 @@ +// compile-pass + +// Regression test related to #56288. Check that a supertrait projection (of +// `Output`) that references `Self` is ok if there is another occurence of +// the same supertrait that specifies the projection explicitly, even if +// the projection's associated type is not explicitly specified in the object type. +// +// Note that in order for this to compile, we need the `Self`-referencing projection +// to normalize fairly directly to a concrete type, otherwise the trait resolver +// will hate us. +// +// There is a test in `trait-object-with-self-in-projection-output-bad.rs` that +// having a normalizing, but `Self`-containing projection does not *by itself* +// allow you to avoid writing the projected type (`Output`, in this example) +// explicitly. + +trait ConstI32 { + type Out; +} + +impl<T: ?Sized> ConstI32 for T { + type Out = i32; +} + +trait Base { + type Output; +} + +trait NormalizingHelper: Base<Output=<Self as ConstI32>::Out> + Base<Output=i32> { + type Target; +} + +impl Base for u32 +{ + type Output = i32; +} + +impl NormalizingHelper for u32 +{ + type Target = i32; +} + +fn main() { + // Make sure this works both with and without the associated type + // being specified. + let _x: Box<dyn NormalizingHelper<Target=i32>> = Box::new(2u32); + let _y: Box<dyn NormalizingHelper<Target=i32, Output=i32>> = Box::new(2u32); +} |