Has Grammar::Debugger bitrotted?

golfed-grammar-debugger.p6

my class C is Mu is Metamodel::GrammarHOW {
    has $!x;
    
    method find_method($obj, $name) {
        return callsame if $name eq any(<parse CREATE BUILD Bool defined MATCH>);
        -> $c, |args { self.y($name) };
    }
    
    method y($name) {
        $!x = 1;
    }
    
    method publish_method_cache($obj) {
    }
}

my module EXPORTHOW { }
EXPORTHOW::<grammar> = C;

output.txt

$ PERL6LIB=lib perl6 -e 'use Grammar::Debugger; grammar G { regex TOP { hi } }; G.parse("hi")'
TOP
> 
Cannot modify an immutable Bool
  in block  at .../lib/Grammar/Debugger.pm:77
  in block  at .../lib/Grammar/Debugger.pm:75
  in method intervene at .../lib/Grammar/Debugger.pm:70
  in block  at .../lib/Grammar/Debugger.pm:45
  in method parse at src/gen/m-CORE.setting:13041
  in block  at -e:1

Underlying error:

$ PERL6LIB=lib perl6 -e 'use Grammar::Debugger; grammar G { regex TOP { hi } }; G.parse("hi")'
No such method 'TOP' for invocant of type 'Bool'
  in method parse at src/gen/m-CORE.setting:13239
  in block  at -e:1