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The SCCs of the region graph are not a reliable heuristic to use for blaming an interesting constraint for diagnostics. For region errors, if the outlived region is `'static`, or the involved types are invariant in their lifetiems, there will be cycles in the constraint graph containing both the target region and the most interesting constraints to blame. To get better diagnostics in these cases, this commit removes that heuristic.
33 lines
1.4 KiB
Plaintext
33 lines
1.4 KiB
Plaintext
error[E0596]: cannot borrow `y` as mutable, as it is not declared as mutable
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--> $DIR/ex3-both-anon-regions-using-trait-objects.rs:2:3
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LL | y.push(z);
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| ^ cannot borrow as mutable
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help: consider changing this to be mutable
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LL | fn foo(x:Box<dyn Fn(&u8, &u8)> , mut y: Vec<&u8>, z: &u8) {
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| +++
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error: lifetime may not live long enough
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--> $DIR/ex3-both-anon-regions-using-trait-objects.rs:2:3
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LL | fn foo(x:Box<dyn Fn(&u8, &u8)> , y: Vec<&u8>, z: &u8) {
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| - - let's call the lifetime of this reference `'1`
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| |
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| let's call the lifetime of this reference `'2`
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LL | y.push(z);
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| ^^^^^^^^^ argument requires that `'1` must outlive `'2`
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= note: requirement occurs because of a mutable reference to `Vec<&u8>`
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= note: mutable references are invariant over their type parameter
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= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
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help: consider introducing a named lifetime parameter
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LL | fn foo<'a>(x:Box<dyn Fn(&u8, &u8)> , y: Vec<&'a u8>, z: &'a u8) {
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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 E0596`.
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