Rust Error E0737: Requirements for #[track_caller] Attribute

Understanding Rust Error E0737

Error E0737 relates to misuse of the #[track_caller] attribute, which extends Rust's error reporting capabilities on panics. The attribute is utilized to mark functions to implicitly receive caller location data. When a function marked with #[track_caller] panics, Rust provides more detailed error information that includes caller location.

The error code E0737 arises when a function defined with #[track_caller] does not follow its expected restrictions. In order to avoid this error, the function must have the "Rust" ABI associated with it.

Erroneous Example

#![allow(unused)]
fn main() {
#[track_caller]
extern "C" fn foo() {}
}

In the example above, the error occurs as the function 'foo' with #[track_caller] attribute is defined with an external "C" ABI instead of the "Rust" ABI.

Fixing Rust Error E0737

To fix this error, ensure that any function using the #[track_caller] attribute is not defined with an external ABI and instead uses the "Rust" ABI.

Correct Example

#![allow(unused)]
fn main() {
#[track_caller]
fn foo() {}
}

In the corrected example above, the 'foo' function defined with #[track_caller] does not use any external ABI, and thus it uses the "Rust" ABI by default.

Conclusion