Readonly: Explicit Readonly Keywords
There are a few places where an explicit readonly keyword is required when using readonly values.
Calling a readonly function
Calling a function or method that returns readonly requires wrapping the result in a readonly expression.
class Foo {}
function returns_readonly(): readonly Foo {
return readonly new Foo();
}
function test(): void {
$x = readonly returns_readonly(); // this is required to call returns_readonly()
}
Accessing readonly properties
Accessing a readonly property (i.e. a property annotated readonly at the declaration, not accessing a property off of a readonly object) requires readonly annotation.
class Bar {}
class Foo {
public function __construct(
public readonly Bar $bar,
) {}
}
function test(Foo $f): void {
$bar = readonly $f->bar; // this is required
}
Interactions with Coeffects
If your function has the ReadGlobals capability but not the AccessGlobals capability (i.e. is marked read_globals or leak_safe), it can only access class static variables if they are wrapped in a readonly expression:
<<file:__EnableUnstableFeatures("readonly")>>
class Bar {}
class Foo {
public static readonly ?Bar $bar = null;
}
function read_static()[read_globals]: void {
$y = readonly Foo::$bar; // keyword required
}
function read_static2()[leak_safe]: void {
$y = readonly Foo::$bar; // keyword required
}
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