Rust errors / Types and traits
Rust compiler error · checked with rustc 1.99.0
Rust error E0735: generic parameters cannot use `Self` in their defaults
What it meansType parameter defaults cannot use Self on structs, enums, or unions.
What rustc prints
error[E0735]: generic parameters cannot use `Self` in their defaults
--> main.rs:1:20
|
1 | struct Foo<X = Box<Self>> {
| ^^^^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.
E0735Types and traits
Activein rustc 1.99.0
8related errors linked below
The compiler team's explanation
Type parameter defaults cannot use Self on structs, enums, or unions.
Erroneous code example:
struct Foo<X = Box<Self>> {
field1: Option<X>,
field2: Option<X>,
}
// error: type parameters cannot use `Self` in their defaults.From rustc --explain E0735 (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
- E0719the value of the associated type `Item` in trait `Iterator` is already specified
- E0720cannot resolve opaque type
- E0737`#[track_caller]` can only be used with the Rust ABI
- E0740field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
Up next
Often hit nextE0308: mismatched typesA related error from the same family.Read it next →Did this answer your question?