Recursion limit warning encountered too often

[jfecher]

867cfea caused us to try constraints earlier and retry if they fail, which lead to more constraints hitting the recursion limit and issuing a warning before retrying later and succeeding.

The retry behavior is not a bug but the trait solver should be smarter about its impl search such that it either can detect infinite recursion before resorting to the recursion counter (current limit is 10 recursive calls) or the warning should be forever silenced, along with a possible lowering of the recursion limit (to 5? 7?*) since it affects the speed of the trait solver much more now.

The warning has been temporarily disabled for the time being by the same commit.

• 7 or even 5 recursive traits should be sufficient to solve most programs, but one can always construct a trait that requires > 5 given constraints deep. Uncertain as to how common this may be in highly generic libraries.