Add explanation to type mismatch involving type params and assoc types #63907
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r? @eddyb (rust_highfive has picked a reviewer for you, use r? to override) |
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@rust-lang/wg-diagnostics can I get some eyeballs on this? I would like feedback on the copy, verbosity and ideas. |
| - change `foo` to return an argument of type `T`: | ||
| ``` | ||
| impl<T> Trait<T> for X { | ||
| fn foo(&self, x: T) -> T { x } |
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this one confused me since it hinges on changes to the trait def as well as the impl
src/librustc/ty/error.rs
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| db.note("you might be missing a type parameter or trait bound"); | ||
| } | ||
| (ty::Param(_), _) | (_, ty::Param(_)) => { | ||
| db.help("given a type parameter `T` and a method `foo`: |
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Can we gate the long explanations (both of them) under the teaching flag?
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We can, but I'm getting more and more convinced that --teach will not be as useful as focusing on improving the existing default errors. I would like help editing and pruning down the error. We could even give this case a different error code to have somewhere to put these explanations. Then we could have --teach just embed the error code text below the error when they are flagged as not having special support for it... 🤔
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I just think we need to keep in mind folks who have already learned the concept and don't want to be spammed down with very long messages (which are useful to beginners but not familiar folks).
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Agree.
I think it would be better if we just had a section in the book that we could link to explaining this case. Having at most two lines, including link, of text should be reasonable (and is my unofficial cutoff for these kind of messages).
What do you think?
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I'll be getting back to this over the weekend. |
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📌 Commit 479ce39 has been approved by |
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…-obk Add explanation to type mismatch involving type params and assoc types CC rust-lang#63711
Rollup of 9 pull requests Successful merges: - #63907 (Add explanation to type mismatch involving type params and assoc types) - #64615 (rustbuild: Turn down compression on exe installers) - #64617 (rustbuild: Turn down compression on msi installers) - #64618 (rustbuild: Improve output of `dist` step) - #64619 (Fixes #63962. Hint about missing tuple parentheses in patterns) - #64634 (Update to LLVM 9.0.0) - #64635 (Allow using fn pointers in const fn with unleash miri) - #64660 (unify errors for tuple/struct variants) - #64664 (fully remove AstBuilder) Failed merges: r? @ghost
CC #63711