class Foo {
    private final boo;
 
    Foo(boo) { this.boo = boo }
    def bar() { "original $boo" }
}
 
class FooCategory {
    def static bar(Foo self) { "categorical ${self.boo}" }
}
 
def f = new Foo('hello')
 
assert f.bar() == 'original hello'
 
use(FooCategory) { assert f.bar() == 'categorical hello' }
 
class Baz {
    def quux(boo) { new Foo(boo).bar() }
}
 
use(FooCategory) { assert new Baz().quux('no') == 'original no' } // fails as quux returns 'categorical no' even though Foo.bar is not called in this lexical scope!

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