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docs/test: add UI test and docs for E0476

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Ezra Shaw 2023-02-25 19:11:58 +13:00
parent f0bc76ac41
commit 9f876cc900
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5 changed files with 67 additions and 2 deletions
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2
compiler/rustc_error_codes/src/error_codes.rs
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@ -253,6 +253,7 @@ E0466: include_str!("./error_codes/E0466.md"),
E0468: include_str!("./error_codes/E0468.md"),
E0469: include_str!("./error_codes/E0469.md"),
E0472: include_str!("./error_codes/E0472.md"),
E0476: include_str!("./error_codes/E0476.md"),
E0477: include_str!("./error_codes/E0477.md"),
E0478: include_str!("./error_codes/E0478.md"),
E0482: include_str!("./error_codes/E0482.md"),
@ -611,7 +612,6 @@ E0793: include_str!("./error_codes/E0793.md"),
// E0473, // dereference of reference outside its lifetime
// E0474, // captured variable `..` does not outlive the enclosing closure
// E0475, // index of slice outside its lifetime
E0476, // lifetime of the source pointer does not outlive lifetime bound...
// E0479, // the type `..` (provided as the value of a type parameter) is...
// E0480, // lifetime of method receiver does not outlive the method call
// E0481, // lifetime of function argument does not outlive the function call

21
compiler/rustc_error_codes/src/error_codes/E0476.md Normal file
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@ -0,0 +1,21 @@
The coerced type does not outlive the value being coerced to.
Example of erroneous code:
```compile_fail,E0476
#![feature(coerce_unsized)]
#![feature(unsize)]
use std::marker::Unsize;
use std::ops::CoerceUnsized;
// error: lifetime of the source pointer does not outlive lifetime bound of the
// object type
impl<'a, 'b, T, S> CoerceUnsized<&'a T> for &'b S where S: Unsize<T> {}
```
During a coercion, the "source pointer" (the coerced type) did not outlive the
"object type" (value being coerced to). In the above example, `'b` is not a
subtype of `'a`. This error can currently only be encountered with the unstable
`CoerceUnsized` trait which allows custom coercions of unsized types behind a
smart pointer to be implemented.