What is the error of using extend in a mixin with a parameter?

Question

css

We have in LESS

@color-blue: blue;


.mymixin(@color) {      
     
  [email protected]{color} {
  font-size: 1
  }  
  
 .zzz {
  &:extend([email protected]{color});
  }
 
}

.mymixin(blue);

Result

.test-blue {
  font-size: 1;
}

Need to see output

.test-blue, 
.zzz {
  font-size: 1;
}

Here I am debugging

Answer 1

I gave you a link about extend in the last answer. Please read the entire page with examples.
websketches.ru/less/extend