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Diffstat (limited to 'compiler/rustc_error_codes/src/error_codes/E0476.md')
-rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0476.md | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0476.md b/compiler/rustc_error_codes/src/error_codes/E0476.md new file mode 100644 index 000000000..fc141ba77 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0476.md @@ -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. |