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When encountering trait bound errors that satisfy some heuristics that tell us that the relevant trait for the user comes from the root obligation and not the current obligation, we use the root predicate for the main message. This allows to talk about "X doesn't implement Pattern<'_>" over the most specific case that just happened to fail, like "char doesn't implement Fn(&mut char)" in `tests/ui/traits/suggest-dereferences/root-obligation.rs` The heuristics are: - the type of the leaf predicate is (roughly) the same as the type from the root predicate, as a proxy for "we care about the root" - the leaf trait and the root trait are different, so as to avoid talking about `&mut T: Trait` and instead remain talking about `T: Trait` instead - the root trait is not `Unsize`, as to avoid talking about it in `tests/ui/coercion/coerce-issue-49593-box-never.rs`. ``` error[E0277]: the trait bound `&char: Pattern<'_>` is not satisfied --> $DIR/root-obligation.rs:6:38 | LL | .filter(|c| "aeiou".contains(c)) | -------- ^ the trait `Fn<(char,)>` is not implemented for `&char`, which is required by `&char: Pattern<'_>` | | | required by a bound introduced by this call | = note: required for `&char` to implement `FnOnce<(char,)>` = note: required for `&char` to implement `Pattern<'_>` note: required by a bound in `core::str::<impl str>::contains` --> $SRC_DIR/core/src/str/mod.rs:LL:COL help: consider dereferencing here | LL | .filter(|c| "aeiou".contains(*c)) | + ``` Fix #79359, fix #119983, fix #118779, cc #118415 (the suggestion needs to change).
36 lines
1.3 KiB
Plaintext
36 lines
1.3 KiB
Plaintext
error[E0277]: the trait bound `String: Pattern<'_>` is not satisfied
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--> $DIR/issue-104961.rs:4:19
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LL | x.starts_with("hi".to_string() + " you")
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| ----------- ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Pattern<'_>` is not implemented for `String`
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| |
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| required by a bound introduced by this call
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= note: required for `String` to implement `Pattern<'_>`
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note: required by a bound in `core::str::<impl str>::starts_with`
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--> $SRC_DIR/core/src/str/mod.rs:LL:COL
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help: consider borrowing here
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LL | x.starts_with(&("hi".to_string() + " you"))
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| ++ +
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error[E0277]: the trait bound `String: Pattern<'_>` is not satisfied
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--> $DIR/issue-104961.rs:9:19
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LL | x.starts_with("hi".to_string())
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| ----------- ^^^^^^^^^^^^^^^^ the trait `Pattern<'_>` is not implemented for `String`
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| |
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| required by a bound introduced by this call
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= note: required for `String` to implement `Pattern<'_>`
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note: required by a bound in `core::str::<impl str>::starts_with`
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--> $SRC_DIR/core/src/str/mod.rs:LL:COL
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help: consider borrowing here
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LL | x.starts_with(&"hi".to_string())
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| +
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0277`.
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