Master fix 4252

[puckowski]

What:

Fixes issue #4252 where a container query created via mixin would reuse previously evaluated variables leading to incorrect CSS output.

Why:

This should be valid Less.js:

.wrapper {
  container-name: wrapper;
  container-type: size;
}

.my_mixin(@height) {
  @container wrapper (height < @height) {
    a {
      max-height: @height;
    }
  }
}

.my_mixin(100);
.my_mixin(200);
.my_mixin(300);

Currently we produce:

.wrapper {
  container-name: wrapper;
  container-type: size;
}
@container wrapper (height < 100) {
  a {
    max-height: 100;
  }
}
@container wrapper (height < 100) {
  a {
    max-height: 200;
  }
}
@container wrapper (height < 100) {
  a {
    max-height: 300;
  }
}

Checklist:

• Documentation
• Added/updated unit tests
• Code complete

New Less.js output is:

.wrapper {
  container-name: wrapper;
  container-type: size;
}
@container wrapper (height < 100) {
  a {
    max-height: 100;
  }
}
@container wrapper (height < 200) {
  a {
    max-height: 200;
  }
}
@container wrapper (height < 300) {
  a {
    max-height: 300;
  }
}

[puckowski]

I submitted a few PRs. I expect rebase(s) will be needed in order to merge all of them, so let me know when a rebase is needed.