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Understanding Rust Error E0711: Conflicting Stability Requirements

Rust Error E0711: Conflicting Stability Requirements

Error E0711 occurs when a feature in the Rust programming language is declared with conflicting stability requirements. This is an internal error in the compiler and will not be emitted with typical Rust code.

Example of Rust Error E0711

#![feature(staged_api)]

#![stable(feature = "foo", since = "1.0.0")]

#[stable(feature = "foo", since = "1.0.0")]
fn foo_stable_1_0_0() {}

#[stable(feature = "foo", since = "1.29.0")]
fn foo_stable_1_29_0() {}

#[unstable(feature = "foo", issue = "none")]
fn foo_unstable() {}

In the example above, the 'foo' feature is declared as stable since version 1.0.0, then re-declared as stable since version 1.29.0, causing a conflict and triggering the E0711 error. Additionally, 'foo' is defined as unstable, creating another conflict and raising the error.

How to Fix Rust Error E0711

To resolve this error, you should split the conflicting feature, allowing for separate stability requirements and removing any possibility of conflict. It's important to ensure that features are uniquely and consistently defined to avoid this error.

Fixed Example

#![feature(staged_api)]

#![stable(feature = "foo", since = "1.0.0")]

#[stable(feature = "foo", since = "1.0.0")]
fn foo_stable_1_0_0() {}

#![stable(feature = "bar", since = "1.29.0")]

#[stable(feature = "bar", since = "1.29.0")]
fn foo_stable_1_29_0() {}

#[unstable(feature = "baz", issue = "none")]
fn foo_unstable() {}

In this revised example, the features have been split into 'foo', 'bar', and 'baz', each with unique stability requirements, thus resolving the conflicts and correcting the error.

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