scoping gotcha with Groovy Categories

CategoryGotcha.groovy

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!

Foo.groovy

class Foo {
    private final boo;
    
    Foo(boo) { this.boo = boo }
    def bar() { "original $boo" }
}

FooCategory.groovy

class FooCategory {
    def static bar(Foo self) { "categorical ${self.boo}" }
}

@olabini pointed out to me that Groovy's categories are runtime-scoped, not lexically-scoped

run this at http://groovyconsole.appspot.com/script/433001 or https://ideone.com/V1Z9E