Auto merge of #96195 - sunfishcode:sunfishcode/handle-or-error-type, r=joshtriplett
Define a dedicated error type for `HandleOrNull` and `HandleOrInvalid`. Define `NullHandleError` and `InvalidHandleError` types, that implement std::error::Error, and use them as the error types in `HandleOrNull` and `HandleOrInvalid`, This addresses [this concern](https://github.com/rust-lang/rust/issues/87074#issuecomment-1080031167). This is the same as #95387. r? `@joshtriplett`
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commit
bb85bcaca9
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@ -76,7 +76,7 @@ pub struct OwnedHandle {
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/// `NULL`. This ensures that such FFI calls cannot start using the handle without
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/// checking for `NULL` first.
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///
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/// This type concerns any value other than `NULL` to be valid, including `INVALID_HANDLE_VALUE`.
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/// This type considers any value other than `NULL` to be valid, including `INVALID_HANDLE_VALUE`.
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/// This is because APIs that use `NULL` as their sentry value don't treat `INVALID_HANDLE_VALUE`
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/// as special.
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///
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@ -96,7 +96,7 @@ pub struct HandleOrNull(OwnedHandle);
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/// `INVALID_HANDLE_VALUE`. This ensures that such FFI calls cannot start using the handle without
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/// checking for `INVALID_HANDLE_VALUE` first.
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///
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/// This type concerns any value other than `INVALID_HANDLE_VALUE` to be valid, including `NULL`.
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/// This type considers any value other than `INVALID_HANDLE_VALUE` to be valid, including `NULL`.
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/// This is because APIs that use `INVALID_HANDLE_VALUE` as their sentry value may return `NULL`
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/// under `windows_subsystem = "windows"` or other situations where I/O devices are detached.
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///
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@ -143,17 +143,17 @@ impl BorrowedHandle<'_> {
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}
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impl TryFrom<HandleOrNull> for OwnedHandle {
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type Error = ();
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type Error = NullHandleError;
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#[inline]
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fn try_from(handle_or_null: HandleOrNull) -> Result<Self, ()> {
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fn try_from(handle_or_null: HandleOrNull) -> Result<Self, NullHandleError> {
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let owned_handle = handle_or_null.0;
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if owned_handle.handle.is_null() {
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// Don't call `CloseHandle`; it'd be harmless, except that it could
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// overwrite the `GetLastError` error.
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forget(owned_handle);
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Err(())
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Err(NullHandleError(()))
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} else {
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Ok(owned_handle)
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}
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@ -201,23 +201,59 @@ impl OwnedHandle {
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}
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impl TryFrom<HandleOrInvalid> for OwnedHandle {
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type Error = ();
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type Error = InvalidHandleError;
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#[inline]
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fn try_from(handle_or_invalid: HandleOrInvalid) -> Result<Self, ()> {
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fn try_from(handle_or_invalid: HandleOrInvalid) -> Result<Self, InvalidHandleError> {
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let owned_handle = handle_or_invalid.0;
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if owned_handle.handle == c::INVALID_HANDLE_VALUE {
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// Don't call `CloseHandle`; it'd be harmless, except that it could
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// overwrite the `GetLastError` error.
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forget(owned_handle);
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Err(())
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Err(InvalidHandleError(()))
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} else {
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Ok(owned_handle)
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}
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}
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}
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/// This is the error type used by [`HandleOrNull`] when attempting to convert
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/// into a handle, to indicate that the value is null.
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// The empty field prevents constructing this, and allows extending it in the future.
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#[unstable(feature = "io_safety", issue = "87074")]
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct NullHandleError(());
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#[unstable(feature = "io_safety", issue = "87074")]
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impl fmt::Display for NullHandleError {
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fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
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"A HandleOrNull could not be converted to a handle because it was null".fmt(fmt)
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}
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}
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#[unstable(feature = "io_safety", issue = "87074")]
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impl crate::error::Error for NullHandleError {}
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/// This is the error type used by [`HandleOrInvalid`] when attempting to
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/// convert into a handle, to indicate that the value is
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/// `INVALID_HANDLE_VALUE`.
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// The empty field prevents constructing this, and allows extending it in the future.
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#[unstable(feature = "io_safety", issue = "87074")]
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct InvalidHandleError(());
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#[unstable(feature = "io_safety", issue = "87074")]
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impl fmt::Display for InvalidHandleError {
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fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
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"A HandleOrInvalid could not be converted to a handle because it was INVALID_HANDLE_VALUE"
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.fmt(fmt)
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}
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}
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#[unstable(feature = "io_safety", issue = "87074")]
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impl crate::error::Error for InvalidHandleError {}
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impl AsRawHandle for BorrowedHandle<'_> {
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#[inline]
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fn as_raw_handle(&self) -> RawHandle {
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@ -0,0 +1,39 @@
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error[E0277]: the trait bound `(): std::error::Error` is not satisfied
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--> $DIR/coerce-issue-49593-box-never-windows.rs:18:53
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LL | /* *mut $0 is coerced to Box<dyn Error> here */ Box::<_ /* ! */>::new(x)
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| ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::error::Error` is not implemented for `()`
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= help: the following other types implement trait `std::error::Error`:
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!
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&'a T
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AccessError
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AddrParseError
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Arc<T>
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BorrowError
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BorrowMutError
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Box<T>
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and 45 others
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= note: required for the cast to the object type `dyn std::error::Error`
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error[E0277]: the trait bound `(): std::error::Error` is not satisfied
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--> $DIR/coerce-issue-49593-box-never-windows.rs:23:49
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LL | /* *mut $0 is coerced to *mut Error here */ raw_ptr_box::<_ /* ! */>(x)
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::error::Error` is not implemented for `()`
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= help: the following other types implement trait `std::error::Error`:
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!
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&'a T
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AccessError
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AddrParseError
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Arc<T>
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BorrowError
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BorrowMutError
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Box<T>
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and 45 others
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= note: required for the cast to the object type `(dyn std::error::Error + 'static)`
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0277`.
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58
src/test/ui/coercion/coerce-issue-49593-box-never-windows.rs
Normal file
58
src/test/ui/coercion/coerce-issue-49593-box-never-windows.rs
Normal file
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@ -0,0 +1,58 @@
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// revisions: nofallback fallback
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// only-windows - the number of `Error` impls is platform-dependent
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//[fallback] check-pass
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//[nofallback] check-fail
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#![feature(never_type)]
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#![cfg_attr(fallback, feature(never_type_fallback))]
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#![allow(unreachable_code)]
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use std::error::Error;
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use std::mem;
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fn raw_ptr_box<T>(t: T) -> *mut T {
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panic!()
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}
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fn foo(x: !) -> Box<dyn Error> {
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/* *mut $0 is coerced to Box<dyn Error> here */ Box::<_ /* ! */>::new(x)
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//[nofallback]~^ ERROR trait bound `(): std::error::Error` is not satisfied
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}
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fn foo_raw_ptr(x: !) -> *mut dyn Error {
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/* *mut $0 is coerced to *mut Error here */ raw_ptr_box::<_ /* ! */>(x)
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//[nofallback]~^ ERROR trait bound `(): std::error::Error` is not satisfied
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}
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fn no_coercion(d: *mut dyn Error) -> *mut dyn Error {
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/* an unsize coercion won't compile here, and it is indeed not used
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because there is nothing requiring the _ to be Sized */
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d as *mut _
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}
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trait Xyz {}
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struct S;
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struct T;
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impl Xyz for S {}
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impl Xyz for T {}
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fn foo_no_never() {
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let mut x /* : Option<S> */ = None;
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let mut first_iter = false;
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loop {
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if !first_iter {
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let y: Box<dyn Xyz>
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= /* Box<$0> is coerced to Box<Xyz> here */ Box::new(x.unwrap());
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}
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x = Some(S);
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first_iter = true;
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}
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let mut y : Option<S> = None;
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// assert types are equal
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mem::swap(&mut x, &mut y);
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}
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fn main() {
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}
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@ -1,5 +1,5 @@
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error[E0277]: the trait bound `(): std::error::Error` is not satisfied
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--> $DIR/coerce-issue-49593-box-never.rs:17:53
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--> $DIR/coerce-issue-49593-box-never.rs:18:53
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LL | /* *mut $0 is coerced to Box<dyn Error> here */ Box::<_ /* ! */>::new(x)
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| ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::error::Error` is not implemented for `()`
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@ -17,7 +17,7 @@ LL | /* *mut $0 is coerced to Box<dyn Error> here */ Box::<_ /* ! */>::new(x
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= note: required for the cast to the object type `dyn std::error::Error`
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error[E0277]: the trait bound `(): std::error::Error` is not satisfied
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--> $DIR/coerce-issue-49593-box-never.rs:22:49
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--> $DIR/coerce-issue-49593-box-never.rs:23:49
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LL | /* *mut $0 is coerced to *mut Error here */ raw_ptr_box::<_ /* ! */>(x)
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::error::Error` is not implemented for `()`
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@ -1,4 +1,5 @@
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// revisions: nofallback fallback
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// ignore-windows - the number of `Error` impls is platform-dependent
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//[fallback] check-pass
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//[nofallback] check-fail
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