Guarded namespace unavailable when calling mixin with ruleset

I keep running into issues today it seems.

Example:

#media {
  #desktop (@ruleset) {
    @media (min-width: 700px) {
      @ruleset();
    }
  }

  #mobile (@ruleset) {
    @media (max-width: 699px) {
      @ruleset();
    }
  }
}


@switch: demo;

.example {
  #lookup when (@switch = demo) {
    @not-found: 1;
  }

  @found: 2;
  
  #lookup2 {
    @also-found: 3;
  }

  
  #media#desktop({
    // Comment the next line and it will all compile
    error: #lookup[@not-found];
    success1: @found;
    success2: #lookup2[@also-found];
  });
}

Expected output:

@media (min-width: 700px) {
  .example {
    error: 1;
    success1: 2;
    success2: 3;
  }
}

Actual output: variable @not-found not found .

I managed to narrow it down to usage of the guard. Remove it and it works. Put the namespace within the ruleset and it works.

Reproduce the supplied Less example and confirm that the guarded namespace call fails while the unguarded variant succeeds. Trace the compiler path for guarded namespace lookup and add a regression test covering the expected CSS output; done when @not-found resolves to 1 without breaking the other properties.