Suppose the following ParamSet:

> ps <- ParamSet$new(list(
  ParamLgl$new("x", default = TRUE),
  ParamLgl$new("y")))
> ps$add_dep("y", "x", CondEqual$new(TRUE))

Here the default = TRUE indicates that, if the parameter x is not given, the whole thing should behave like x is set to TRUE. E.g. x could indicate whether a certain feature is used, and y could then influence the configuration of that feature---y then depends on x being TRUE, since it does not have anything to configure if x is FALSE.

Since the "default" behaviour indicated is that the feature is usually present (everything behaves like x is TRUE) if x is not given at all, it makes sense to just set the y parameter and have the x parameter be "implicitly" TRUE.

This is not what happens, however:

> ps$values <- list(y = TRUE)
Error in (function (xs)  : 
  Assertion on 'xs' failed: The parameter 'y' can only be set if the following condition is met 'x = TRUE'. Instead the parameter value for 'x' is not set at all. Try setting 'x' to a value that satisfies the condition.

The ParamSet$check() function should do an xs = insert_named(self$default, xs) after the if(!isTRUE(ok)) block. What I am describing above should be added as a test; possibly add more tests.

(I believe one of our student assistants could solve this)