Understanding Rust Error E0050

What is Rust Error E0050?

Rust Error E0050 occurs when a trait method implementation has the incorrect number of function parameters compared to the trait method declaration.

An example of erroneous code:

trait Foo {
    fn foo(&self, x: u8) -> bool;
}

struct Bar;

impl Foo for Bar {
    fn foo(&self) -> bool { true }
}

Error Explanation

The trait Foo has a method foo, which takes two parameters - &self and x with type u8. However, when implementing this trait for the struct Bar, we forgot to include the second parameter, resulting in Rust Error E0050.

How to fix Rust Error E0050

To fix this error, make sure the trait method implementation has the same number of parameters as the trait method declaration.

A corrected code example:

trait Foo {
    fn foo(&self, x: u8) -> bool;
}

struct Bar;

impl Foo for Bar {
    fn foo(&self, x: u8) -> bool { true }
}

Common scenarios and mistakes

In some cases, the missing parameter could be the result of an accidental omission. For example, you might have forgotten to include a parameter when implementing the trait method. Alternatively, the trait method declaration itself might have an extra parameter by mistake.

Preventing Rust Error E0050

To avoid Rust Error E0050, always double-check your trait method implementations and trait method declarations to ensure that they have the correct number of parameters.

If you are changing the signature of a trait method, make sure to update all the implementations to include the correct parameters.

Conclusion

In this article, we have explained Rust Error E0050, which occurs when a trait method implementation has the incorrect number of function parameters compared to the trait method declaration. We have covered how to fix the error, common scenarios and mistakes, and ways to prevent the error from occurring.

Recommended Reading

• Understanding Rust Traits