Add an extended prelude for the 2018 editions #51434
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Yay more prelude. But how will the decision be made for proposed extensions such as: |
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I'm not sure if I think we can, in theory, write lint to the rust-2018-compatibility group that changes calls to methods that become ambiguous to their fully qualified form. But I'd rather hear from @Manishearth who has way more experience with this and can better judge the |
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@leodasvacas I think that a decision for each of these needs to be made on a case-by-case basis, and not necessarily in this PR. @killercup I just checked https://rust-lang.github.io/rfcs/2052-epochs.html#a-broad-policy-on-epoch-changes and having rustfix automate the transition would be nice to have but per the RFC it is a requirement that code that would break warns in the previous edition. Unfortunately I don’t know how to go about implementing that warning… |
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Lint feels a bit tricky to handle. Unsure what edge cases exist, though, so it might not be that tricky. |
| @@ -42,6 +42,7 @@ error[E0573]: expected type, found variant `Ok` | |||
| LL | fn foo() -> Ok { | |||
| | ^^ not a type | |||
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| = help: there is an enum variant `std::prelude::rust2018::Ok`, try using `std::prelude::rust2018`? | |||
| = help: there is an enum variant `std::prelude::v1::Ok`, try using `std::prelude::v1`? | |||
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Just noticed this terrible suggestion. std::prelude::v1 is not an enum!
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Ping from triage! What's the status on this? |
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This is blocked on additional implementation work (a warning on 2015-edition code that would break in the 2018 edition) that I don’t know how to do… or deciding an exception for this “hard requirement” stated in the RFC. |
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Closing for now to make triage easier. This is still tracked at #51418. |
As proposed in #51418.
Update: Per discussion below this PR also needs to add a warning for 2015 edition code that would break with the new prelude. Help wanted: any ideas how to make that happen?