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Don't emit clashing decl lint for FFI-safe enums.

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An example of an FFI-safe enum conversion is when converting
Option<NonZeroUsize> to usize. Because the Some value must be non-zero,
rustc can use 0 to represent the None variant, making this conversion is
safe. Furthermore, it can be relied on (and removing this optimisation
already would be a breaking change).
This commit is contained in:
jumbatm 2020-07-03 20:14:05 +10:00
parent 4da72f5387
commit 3eaead7d51
3 changed files with 137 additions and 25 deletions
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62
src/test/ui/lint/clashing-extern-fn.stderr
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@ -105,5 +105,65 @@ LL | fn draw_point(p: Point);
= note: expected `unsafe extern "C" fn(sameish_members::a::Point)`
found `unsafe extern "C" fn(sameish_members::b::Point)`
warning: 8 warnings emitted
warning: `missing_return_type` redeclared with a different signature
--> $DIR/clashing-extern-fn.rs:208:13
|
LL | fn missing_return_type() -> usize;
| ---------------------------------- `missing_return_type` previously declared here
...
LL | fn missing_return_type();
| ^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
|
= note: expected `unsafe extern "C" fn() -> usize`
found `unsafe extern "C" fn()`
warning: `non_zero_usize` redeclared with a different signature
--> $DIR/clashing-extern-fn.rs:226:13
|
LL | fn non_zero_usize() -> core::num::NonZeroUsize;
| ----------------------------------------------- `non_zero_usize` previously declared here
...
LL | fn non_zero_usize() -> usize;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
|
= note: expected `unsafe extern "C" fn() -> std::num::NonZeroUsize`
found `unsafe extern "C" fn() -> usize`
warning: `non_null_ptr` redeclared with a different signature
--> $DIR/clashing-extern-fn.rs:228:13
|
LL | fn non_null_ptr() -> core::ptr::NonNull<usize>;
| ----------------------------------------------- `non_null_ptr` previously declared here
...
LL | fn non_null_ptr() -> *const usize;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
|
= note: expected `unsafe extern "C" fn() -> std::ptr::NonNull<usize>`
found `unsafe extern "C" fn() -> *const usize`
warning: `option_non_zero_usize_incorrect` redeclared with a different signature
--> $DIR/clashing-extern-fn.rs:254:13
|
LL | fn option_non_zero_usize_incorrect() -> usize;
| ---------------------------------------------- `option_non_zero_usize_incorrect` previously declared here
...
LL | fn option_non_zero_usize_incorrect() -> isize;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
|
= note: expected `unsafe extern "C" fn() -> usize`
found `unsafe extern "C" fn() -> isize`
warning: `option_non_null_ptr_incorrect` redeclared with a different signature
--> $DIR/clashing-extern-fn.rs:256:13
|
LL | fn option_non_null_ptr_incorrect() -> *const usize;
| --------------------------------------------------- `option_non_null_ptr_incorrect` previously declared here
...
LL | fn option_non_null_ptr_incorrect() -> *const isize;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
|
= note: expected `unsafe extern "C" fn() -> *const usize`
found `unsafe extern "C" fn() -> *const isize`
warning: 13 warnings emitted