ParseError with variable interpolation after ':' in selector

[plumbojumbo]

This succeeds:

(new Less_Parser())->parse('@position: after; .@{position} {}');

This, however, fails:

(new Less_Parser())->parse('@position: after; &:@{position} {}');

ParseError: Unexpected input in anonymous-file-2.less on line 1, column 14
1| @foo: after; &:@{foo} {}

Both Less.js and lessphp compile it just fine. (cmp.)

[Krinkle]

I have confirmed that this passes on the specific Less.js version we aim to support (Less.js 2.5.3), e.g. via fiddle.

@position: after;

.foo {
    &:@{position} {
        color: green;
    }
}

Which Less.js 2.5.3 compiles to:

.foo:after {
  color: green;
}