Multiple ampersands do not produce a syntax error.

[knpwrs]

Tested in less.js 1.6.0.

The following code has very predictable output:

p {
  .foo {
    font-weight: bold;
    &.bar {
      color: red;
    }
  }
}

As such:

p .foo {
  font-weight: bold;
}
p .foo.bar {
  color: red;
}

Being the smartass I am, I then decided I wanted to know what would happen if I tried multiple ampersands:

p {
  .foo {
    font-weight: bold;
    &&.bar {
      color: red;
    }
  }
}

Produces the following css:

p .foo {
  font-weight: bold;
}
p .foop .foo.bar {
  color: red;
}

.foo and p were mashed together to make .foop. I don't know what else should happen -- a syntax error makes the most sense to me. You can also add more ampersands for even more hilarious results:

p {
  .foo {
    font-weight: bold;
    &&&&.bar {
      color: red;
    }
  }
}

Produces:

p .foo {
  font-weight: bold;
}
p .foop .foop .foop .foo.bar {
  color: red;
}

I therefore declare this the foop foop foop bug.

FWIW Sass (SCSS) produces a syntax error with the same code.

[lukeapage]

In general, It is actually a feature, consider

.a {
    & + & {
    }
}

etc.

what is kind of a bug is that it joins together the p and the .foo

[seven-phases-max]

what is kind of a bug is that it joins together the .p and the .foo

I don't think it's a bug either. && should join (unlike & &) see docs#40 for example.

[lukeapage]

Yes, you are right people are using it to postfix everything.
I just think its nice that selectors stay selectors e.g. I might expect in
this example for the p tag to be moved to be p.foo.. anyway it can be
worked around and I agree thus should be closed.