Deprecation

The @deprecated annotation marks a property, callback, or function as deprecated. The compiler warns wherever the member is used from outside the component that declares it, and the warning carries the message the annotation gives it:

component Inner {
    in-out property <int> new-prop;
    @deprecated("Please use 'new-prop' instead") in-out property <int> old-prop <=> new-prop;
}

export component Example {
    inner := Inner { }
    // Warning: The property 'old-prop' has been deprecated: Please use 'new-prop' instead
    out property <int> value: inner.old-prop;
}

slint

The annotation affects diagnostics only. A deprecated member keeps the type, visibility and behavior its declaration gives it, and the compiled result is the same as without the annotation.

Form

@deprecated precedes the declaration, ahead of any visibility or purity modifier, and takes the message in parentheses:

@deprecated("Compute it from 'new-prop' instead") in-out property <int> older-prop: 42;
@deprecated("Use 'new-callback' instead") callback old-callback();
@deprecated("Use 'new-function' instead") public pure function old-function() -> int { 1 }

slint

• The message is mandatory. @deprecated without parentheses is a compile error.
• The message must be a plain string literal. A \{} template expression in it is a compile error.
• A declaration may carry @deprecated only once.

An empty message, @deprecated(""), deprecates the member without advising on a replacement. The warning then names the member and stops, as in The property 'old-prop' has been deprecated.

Warnings

Using a deprecated member is a warning, never an error, so code written against it keeps compiling. Reading it, assigning to it, binding it on an element, aliasing it with <=>, animating it, calling it, and setting a handler for it each warn.

Uses within the component that declares the member don’t warn, since that component still has to implement it.