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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:13 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:13 +0000 |
commit | 218caa410aa38c29984be31a5229b9fa717560ee (patch) | |
tree | c54bd55eeb6e4c508940a30e94c0032fbd45d677 /compiler/rustc_error_codes/src/error_codes/E0377.md | |
parent | Releasing progress-linux version 1.67.1+dfsg1-1~progress7.99u1. (diff) | |
download | rustc-218caa410aa38c29984be31a5229b9fa717560ee.tar.xz rustc-218caa410aa38c29984be31a5229b9fa717560ee.zip |
Merging upstream version 1.68.2+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'compiler/rustc_error_codes/src/error_codes/E0377.md')
-rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0377.md | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0377.md b/compiler/rustc_error_codes/src/error_codes/E0377.md new file mode 100644 index 000000000..b1d364063 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0377.md @@ -0,0 +1,29 @@ +The trait `CoerceUnsized` may only be implemented for a coercion between +structures with the same definition. + +Example of erroneous code: + +```compile_fail,E0377 +#![feature(coerce_unsized)] +use std::ops::CoerceUnsized; + +pub struct Foo<T: ?Sized> { + field_with_unsized_type: T, +} + +pub struct Bar<T: ?Sized> { + field_with_unsized_type: T, +} + +// error: the trait `CoerceUnsized` may only be implemented for a coercion +// between structures with the same definition +impl<T, U> CoerceUnsized<Bar<U>> for Foo<T> where T: CoerceUnsized<U> {} +``` + +When attempting to implement `CoerceUnsized`, the `impl` signature must look +like: `impl CoerceUnsized<Type<U>> for Type<T> where T: CoerceUnsized<U>`; +the *implementer* and *`CoerceUnsized` type parameter* must be the same +type. In this example, `Bar` and `Foo` (even though structurally identical) +are *not* the same type and are rejected. Learn more about the `CoerceUnsized` +trait and DST coercion in +[the `CoerceUnsized` docs](../std/ops/trait.CoerceUnsized.html). |