Rust errors / Types and traits
Rust compiler error · checked with rustc 1.99.0
Rust error E0116: cannot define inherent `impl` for a type outside of the crate where the type is defined
What it meansAn inherent implementation was defined for a type outside the current crate.
What rustc prints
error[E0116]: cannot define inherent `impl` for a type outside of the crate where the type is defined --> main.rs:1:1 | 1 | impl Vec<u8> { } // error | ^^^^^^^^^^^^ impl for type defined outside of crate | = help: consider defining a trait and implementing it for the type or using a newtype wrapper like `struct MyType(ExternalType);` and implement it = note: for more details about the orphan rules, see <https://doc.rust-lang.org/reference/items/implementations.html?highlight=orphan#orphan-rules>
Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.
The compiler team's explanation
An inherent implementation was defined for a type outside the current crate.
Erroneous code example:
impl Vec<u8> { } // errorYou can only define an inherent implementation for a type in the same crate where the type was defined. For example, an impl block as above is not allowed since Vec is defined in the standard library.
To fix this problem, you can either:
- define a trait that has the desired associated functions/types/constants and implement the trait for the type in question
- define a new type wrapping the type and define an implementation on the new type
Note that using the type keyword does not work here because type only introduces a type alias:
type Bytes = Vec<u8>;
impl Bytes { } // error, same as aboveFrom rustc --explain E0116 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
Related errors
- E0308mismatched types
- E0277the trait bound is not satisfied
- E0599no method named X found in the current scope
- E0433failed to resolve
- E0107missing generics for struct `Foo`
- E0109type arguments are not allowed on builtin type `u32`
- E0117only traits defined in the current crate can be implemented for types defined outside of the crate
- E0118no nominal type found for inherent implementation
Up next
Often hit nextE0308: mismatched typesA related error from the same family.Read it next →Did this answer your question?