Rust errors / Types and traits
Rust compiler error · checked with rustc 1.99.0
Rust error E0750: negative impls cannot be default impls
What it meansA negative impl was made default impl.
What rustc prints
error[E0750]: negative impls cannot be default impls
--> main.rs:5:1
|
5 | default impl !MyTrait for u32 {} // error!
| ^^^^^^^ ^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.
E0750Types and traits
Activein rustc 1.99.0
8related errors linked below
The compiler team's explanation
A negative impl was made default impl.
Erroneous code example:
trait MyTrait {
type Foo;
}
default impl !MyTrait for u32 {} // error!Negative impls cannot be default impls. A default impl supplies default values for the items within to be used by other impls, whereas a negative impl declares that there are no other impls. Combining it does not make sense.
From rustc --explain E0750 (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
- E0746return type cannot have an unboxed trait object
- E0749negative impls cannot have any items
- E0751found both positive and negative implementation of trait `MyTrait` for type `i32`:
- E0770the type of const parameters must not depend on other generic parameters
Up next
Often hit nextE0308: mismatched typesA related error from the same family.Read it next →Did this answer your question?