- exprIsBottom should look through type lambdas as evaluting (\ (@ a) -> e) diverges if and only if evaluating e diverges. This was found in the context of Trac #10180.
- New Lint check: no alternatives implies bottoming expression detected either by exprIsBottom or by an empty type. This was suggested by SPJ and fixes Trac #10180.
(will push these two bits sparately.)