Understanding Rust Error E0132

Introduction to Rust Error E0132

Rust Error E0132 occurs when a function with the start attribute is declared with type parameters. In this article, we'll provide a detailed explanation and examples to help you understand and resolve this error.

Understanding the start attribute

The start attribute in Rust can be applied to a function to specify an alternative entry point for the application. To use this attribute, you must enable the start feature in your code. The function with the start attribute should have a specific type signature, as shown below:

fn(isize, *const *const u8) -> isize;

Now let's dive into error E0132 and see how it can be resolved.

Exploring Rust Error E0132

Rust Error E0132 is triggered when a function with the start attribute includes type parameters. The following erroneous code example demonstrates this issue:

#![allow(unused)]
#![feature(start)]

fn main() {
  #[start]
  fn f<T>() {}
}

As mentioned earlier, functions with the start attribute should match the required type signature. In the erroneous code above, the function `f` has a type parameter `T`, which violates the type signature requirements.

Resolving Rust Error E0132

To fix Rust Error E0132, ensure that your function with the start attribute does not include type parameters and matches the required type signature. The corrected code example below demonstrates this:

#![allow(unused)]
#![feature(start)]

fn main() {
  #[start]
  fn my_start(argc: isize, argv: *const *const u8) -> isize {
    0
  }
}

In this corrected code, the function `my_start` does not include type parameters, and it matches the required type signature. As a result, the code will compile without triggering Rust Error E0132.

Conclusion

Rust Error E0132 occurs when a function with the start attribute is declared with type parameters. To resolve this error, ensure that such functions match the required type signature and do not include type parameters. With this information, you should be better equipped to handle and fix Error E0132 in your Rust projects.