Mention implicit T: Sized bound in E0277 errors
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Extracted from #69709. |
rust-highfive
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Also, I'm not sure this PR handles weird cases like |
nikomatsakis
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Mar 9, 2020
| @@ -6,7 +6,7 @@ LL | fn test1<T: ?Sized + Foo>(t: &T) { | |||
| LL | let u: &dyn Foo = t; | |||
| | ^ doesn't have a size known at compile-time | |||
| | | |||
| = help: the trait `std::marker::Sized` is not implemented for `T` | |||
| = help: type parameters have an implicit `Sized` requirement by default | |||
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Huh, these help messages seem to be kind of confusing to me. That is, just looking at the error message, I can't really tell what it's talking about here.
| @@ -12,7 +12,7 @@ LL | mem::size_of::<U>(); | |||
| LL | pub const fn size_of<T>() -> usize { | |||
| | - required by this bound in `std::mem::size_of` | |||
| | | |||
| = help: the trait `std::marker::Sized` is not implemented for `U` | |||
| = help: type parameters have an implicit `Sized` requirement by default | |||
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this is a case where it kind of makes sense, but I feel like we would ideally want it to be in place of the "required by this bound" message. e.g., something like
pub const fn size_of<T>
- required because of the default `Sized` requirement on this type parameter
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