Probable bug with ctxtFromTypedPattern in abs and let cases

[dorchard]

(mostly notes to myself)

I suspect there is a potential for bugs coming from the use of the ctxtFromTypedPattern function when checking/synthing local patterns for lambdas, because ctxtFromTypedPattern generates a predicate relating to the pattern and it also generates a contextual predicate which goes on the head of the tail of the stack (cadr). However in local contexts this contextual predicate needs handling separately (local implication for abs, and immediate use for let).