Cannot namespace detached ruleset

Input

#namespace {
  @ruleset: {
    foo: bar;
  }
}

.my-selector {
  #namespace.@ruleset();
}

Output

ModuleBuildError: Module build failed (from ../node_modules/less-loader/dist/cjs.js):


  .my-selector {
    #namespace.@ruleset();
             ^
Unrecognised input

Aside, the docs seem really unclear about whether a namespace should be declared as #namespace or #namespace(), but it doesn't make a difference either way, in this case.

Start by reproducing the supplied Less input through the less-loader build and compare it with the namespace documentation linked in the report. Trace the parser or namespace handling for #namespace.@ruleset(); done means the detached ruleset invocation is accepted and produces the intended output, with the documentation ambiguity addressed.