LESS & Bootstrap: error evaluation function `darken`: color.toHSL is not a function in the file

Question

I work with MobileAngularUI infrastructure.

When gulp creates a task for my application, with LESS source files overriding some Bootstrap variables, I get a strange error:

Error evaluating function `darken`: color.toHSL is not a function in file /Users/fabio/mobileangularui/bower_components/bootstrap/less/variables.less line no. 382

In my LESS file, I override some variables like this, for example:

@brand-primary: #FF9900;
@my-navbar-link-color: #3399CC;

@navbar-default-color: @brand-primary;
@navbar-default-link-color: @my-navbar-link-color;

What is the problem, why am I getting this error?

Thanks in advance!

Answer 1

The variables.lessvariable is used @navbar-default-brand-color:

@navbar-default-brand-color: @navbar-default-link-color;
@navbar-default-brand-hover-color: darken(@navbar-default-brand-color, 10%);

, , , darken ( LESS native) @my-navbar-link-color, , ( , , )

Answer 2

: transparent