Prohibit unused type parameters in impls. #20593
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r=me after a rebase |
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r=aturon |
nikomatsakis
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parameters on impls must now also appear in the trait ref, self type, or some associated type declared on the impl. This ensures that they are constrianed in some way and that the semantics of the trait system are well-defined (always a good thing). There are three major ways to fix this error: 1. Convert the trait to use associated types; most often the type parameters are not constrained because they are in fact outputs of the impl. 2. Move the type parameters to methods. 3. Add an additional type parameter to the self type or trait so that the unused parameter can appear there. In some cases, it is not possible to fix the impl because the trait definition needs to be changed first (and that may be out of your control). In that case, for the time being, you can opt out of these rules by using `#[old_impl_check]` on the impl and adding a `#![feature(old_impl_check)]` to your crate declaration.
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Make check passes locally. |
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Giving p=1 because this should land for alpha, but it's not supercritical. |
alexcrichton
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Jan 7, 2015
Conflicts: src/libcollections/lib.rs src/librustc/lib.rs src/libserialize/lib.rs src/libstd/lib.rs
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Per rust-lang/rfcs#447
r? @aturon