implicit mixin with variable class name

[tlindig]

I try to include definitions from a class of FontAwesome in my less files.
FontAwesome use class names, build at runtime with a variable to be able to support custom prefixes.

Here is an example I tried at less2css.org

.@{fa-css-prefix} { display: inline-block; }
.@{fa-css-prefix}-2x { font-size: 2em; }

.my-class {
  .@{fa-css-prefix};
  .@{fa-css-prefix}-2x;
}

@fa-css-prefix:       my-icon;

And I got the error message:

Parse error: Unrecognised input
.my-class {      .@{fa-css-prefix};        .@{fa-css-prefix}-2x;

I could only choose version 1.6.0 (current), 1.6.1 was not available in less2css.org.

What is wrong with this example? How can I get the implicit mixin?

[tlindig]

After some more tries, I found a way. But is this the recommended solution?

I replaced the variable with it value.

.@{fa-css-prefix} { display: inline-block; }
.@{fa-css-prefix}-2x { font-size: 2em; }

.my-class {
  .my-icon;
  .my-icon-2x;
}

@fa-css-prefix: my-icon;

[seven-phases-max]

In #1838 I linked to this SO topic with two possible solutions