Rust errors / Types and traits
Rust compiler error · checked with rustc 1.99.0
Rust error E0367: `Drop` impl requires `T: Foo` but the struct it is implemented for does not
What it meansAn attempt was made to implement Drop on a specialization of a generic type.
What rustc prints
error[E0367]: `Drop` impl requires `T: Foo` but the struct it is implemented for does not --> main.rs:7:9 | 7 | impl<T: Foo> Drop for MyStruct<T> { | ^^^ | note: the implementor must specify the same requirement --> main.rs:3:1 | 3 | struct MyStruct<T> { | ^^^^^^^^^^^^^^^^^^
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 attempt was made to implement Drop on a specialization of a generic type.
Erroneous code example:
trait Foo {}
struct MyStruct<T> {
t: T
}
impl<T: Foo> Drop for MyStruct<T> {
fn drop(&mut self) {}
}This code is not legal: it is not possible to specialize Drop to a subset of implementations of a generic type. In order for this code to work, MyStruct must also require that T implements Foo. Alternatively, another option is to wrap the generic type in another that specializes appropriately:
trait Foo{}
struct MyStruct<T> {
t: T
}
struct MyStructWrapper<T: Foo> {
t: MyStruct<T>
}
impl <T: Foo> Drop for MyStructWrapper<T> {
fn drop(&mut self) {}
}From rustc --explain E0367 (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
- E0364`foo` is private, and cannot be re-exported
- E0366`Drop` impls cannot be specialized
- E0368binary assignment operation `<<=` cannot be applied to type `f32`
- E0369binary operation cannot be applied to type
Up next
Often hit nextE0308: mismatched typesA related error from the same family.Read it next →Did this answer your question?