I think the warning is actually valid. The static type of the variable is '(V, V) -> int' and the static type of the method is '(Comparable, Comparable) -> int' and those types are not assignable to each other.

But while the warning is valid, the error message is confusing. It should at least contain actual types something like

  A value of type '(Comparable, Comparable) -> int' is not assignable to a variable of type '(V, V) -> int'

Added this to the 1.5 milestone.
Removed Priority-Unassigned label.
Added Priority-Medium, Analyzer-UX labels.

Ok, the warning message did confuse me. Changing the type parameter declaration to V extends Comparable<V> fixes the warning too.

Removed this from the 1.5 milestone.
Added this to the 1.6 milestone.

Removed this from the 1.6 milestone.
Added Oldschool-Milestone-1.6 label.

Removed Oldschool-Milestone-1.6 label.
Changed the title to: "Confusing warning message on assignment to typedefs with type parameters".

The message has been updated to read "A value of type 'Comparable' cannot be assigned to a variable of type 'V'".

Added Fixed label.

Added this to the 1.8 milestone.