Mixin in a namespace sometimes errors when referring to nested sibling mixin.

[Jimbly]

This less code generates an error about ".sub is undefined":

.someclass { #namespace > .mixin(#F00); }
#namespace {
  .sub(@arg1) { background-color: @arg1; }
  .mixin(@color1) { .sub(@color1); }
}

But, none of the following do, which seems inconsistent. If the namespace is first, there is no error:

#namespace {
  .sub(@arg1) { background-color: @arg1; }
  .mixin(@color1) { .sub(@color1); }
}
.someclass { #namespace > .mixin(#F00); }

Or if the the error-generating mixin is moved out a scope level higher (but still later in the file):

.someclass { #namespace > .mixin(#F00); }
#namespace {
  .mixin(@color1) { .sub(@color1); }
}
.sub(@arg1) { background-color: @arg1; }

Or if it is referenced more explicitly:

.someclass { #namespace > .mixin(#F00); }
#namespace {
  .sub(@arg1) { background-color: @arg1; }
  .mixin(@color1) { #namespace > .sub(@color1); }
}

I could not find any reference in the documentation about whether or not order was required for mixins to work, though empirically it seems fine to reference a mixin defined after you reference it. It just seems to fail in this one case where referencing a mixin in a namespace which is referencing another mixin in the same namespace and all of this is after the first reference.

[SomMeri]

I think that this is duplicate of the #996 issue. The other one is labeled as a bug, but it is difficult to fix.

Solution for now is to define the namespace before using it. This works correctly:

#namespace {
  .sub(@arg1) { background-color: @arg1; }
  .mixin(@color1) { .sub(@color1); }
}
.someclass { #namespace > .mixin(#F00); }

I'm closing this as a duplicate. Leave the comment or re-open if you disagree.