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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /compiler/rustc_error_codes/src/error_codes/E0692.md | |
parent | Initial commit. (diff) | |
download | rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip |
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'compiler/rustc_error_codes/src/error_codes/E0692.md')
-rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0692.md | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0692.md b/compiler/rustc_error_codes/src/error_codes/E0692.md new file mode 100644 index 000000000..596cb1e77 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0692.md @@ -0,0 +1,49 @@ +A `repr(transparent)` type was also annotated with other, incompatible +representation hints. + +Erroneous code example: + +```compile_fail,E0692 +#[repr(transparent, C)] // error: incompatible representation hints +struct Grams(f32); +``` + +A type annotated as `repr(transparent)` delegates all representation concerns to +another type, so adding more representation hints is contradictory. Remove +either the `transparent` hint or the other hints, like this: + +``` +#[repr(transparent)] +struct Grams(f32); +``` + +Alternatively, move the other attributes to the contained type: + +``` +#[repr(C)] +struct Foo { + x: i32, + // ... +} + +#[repr(transparent)] +struct FooWrapper(Foo); +``` + +Note that introducing another `struct` just to have a place for the other +attributes may have unintended side effects on the representation: + +``` +#[repr(transparent)] +struct Grams(f32); + +#[repr(C)] +struct Float(f32); + +#[repr(transparent)] +struct Grams2(Float); // this is not equivalent to `Grams` above +``` + +Here, `Grams2` is a not equivalent to `Grams` -- the former transparently wraps +a (non-transparent) struct containing a single float, while `Grams` is a +transparent wrapper around a float. This can make a difference for the ABI. |