Parent selector interpolation in @extend

[garetht]

When attempting to reference the parent selector from within an extended placeholder, attempting to access its value through interpolation does not work:

%foo {
  height: 20px;
  &.baz {
    width: 20px;
  }
  @at-root #{&}-baz {
    width: 20px;
  }
}

.bar {
  @extend %foo;
}

produces (in 3.4.7)

.bar {
  height: 20px;
}
.baz.bar {
  width: 20px;
}

It seems the parent selector works fine to produce .baz.bar, but unexpectedly the rule .bar-baz is missing.

[nex3]

Duplicate of #1455.