In some limited cases, suggest where bounds for non-type params
#82194
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Feb 18, 2021
| @@ -9,6 +9,10 @@ help: consider removing the leading `&`-reference | |||
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| LL | let mut stream_reader = BufReader::new(stream); | |||
| | -- | |||
| help: consider introducing a `where` bound, but there might be an alternative better way to express this requirement | |||
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| LL | fn issue_81421<T: Read + Write>(mut stream: T) where &T: std::io::Read { | |||
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Is this syntax even allowed? where &T: .. will not compile due to missing lifetime parameters unfortunately
error[E0637]: `&` without an explicit lifetime name cannot be used here
--> src/lib.rs:2:23
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2 | fn foo<T>(x: T) where &T: std::io::Read { }
| ^ explicit lifetime name needed hereThere was a problem hiding this comment.
We (I?) allow for limited "mistakes" in the suggested code as long as the compiler gives you further suggestions that lead you to working code. We can gate this suggestion in particular or/and extend E0637 to suggest where a lifetime can be added (we already have suggestions to extend foo's type param list and to add a for lifetime in other places).
Indeed writing where for<'a> &'a T: Read compiles successfully.
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Filed #82312 to track that potential work.
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…n, r=petrochenkov In some limited cases, suggest `where` bounds for non-type params Partially address rust-lang#81971.
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Rollup of 10 pull requests Successful merges: - rust-lang#81546 ([libtest] Run the test synchronously when hitting thread limit) - rust-lang#82066 (Ensure valid TraitRefs are created for GATs) - rust-lang#82112 (const_generics: Dont evaluate array length const when handling yet another error ) - rust-lang#82194 (In some limited cases, suggest `where` bounds for non-type params) - rust-lang#82215 (Replace if-let and while-let with `if let` and `while let`) - rust-lang#82218 (Make sure pdbs are copied along with exe and dlls when bootstrapping) - rust-lang#82236 (avoid converting types into themselves (clippy::useless_conversion)) - rust-lang#82246 (Add long explanation for E0549) - rust-lang#82248 (Optimize counting digits in line numbers during error reporting) - rust-lang#82256 (Print -Ztime-passes (and misc stats/logs) on stderr, not stdout.) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Partially address #81971.